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August 1994
- 5 participants
- 8 discussions
Dear folks,
this is the *2nd* draft agenda for the Lisbon Database-WG meeting.
Thanks for the input received so far!
I tried to
- slightly rearrange the individual items
- key the topics indicating the type of activity expected
- provide a list of references to have ourselves prepared :-)
Any feedback appreciated!
Wilfried.
--------------------------------------------------------------------------------
2nd Draft: Proposed Agenda for the DB-Working-Group at RIPE-19, Lisbon.
-----------------------------------------------------------------------
0. Opening (30')
. appointment of scribe
. amendment/rearrangement of agenda
. any admin stuff
I . review of DB-WG in the context of a changing RIPE
x. The Classless Database (60')
S . review of beta (as announced by Marten Terpstra)
S . review of requirements and scheduled changes
A . (ripe-clarep, ripe-inetnum) document review, and decision
x. Database Operations Review (60')
A . (ripe-auth) proposed guardian mechanism changes
A . (inet-rtr) proposed router object review and decision
A . RIPE-Handles (flag day?)
I . any loose ends? (experiences)
I . ownership of objects, update, coordination (Daniel Kalchev)
I . need for new types of lookup/backlinks? (Havard Eidnes)
x. Interworking with other regions (30')
S . DB-Exchange (status)
S . RWhois, aggrwalk, ...
x. CLNS Routing Registry (10')
A . status review and decision about further activities
Z. AOB
Key:
I ... Informal discussion
S ... review of Status, on-going
A ... discussion and Approval requested
Supporting documents:
ftp://ftp.ripe.net/ripe/drafts/ripe-clarep.txt
ftp://ftp.ripe.net/ripe/drafts/ripe-inetnum.txt
ftp://ftp.ripe.net/ripe/drafts/inet-rtr.txt
ftp://ftp.ripe.net/ripe/drafts/ripe-auth.txt
(a "transition document" to be announced by the NCC)
--------------------------------------------------------------------------
Wilfried Woeber : e-mail: Wilfried.Woeber(a)CC.UniVie.ac.at
Computer Center - ACOnet :
Vienna University : Tel: +43 1 4065822 355
Universitaetsstrasse 7 : Fax: +43 1 4065822 170
A-1010 Vienna, Austria, Europe : NIC: WW144
--------------------------------------------------------------------------
1
0
Dear folks,
attached is the *1st* attempt on a draft agenda for the Lisbon
Database-WG meeting. Due to the fact that I'll leave Vienna on Monday
the 5th of September, I'd ask for comments, suggestions, etc. before
Friday to allow for distribution of the next draft agenda to the
ripe-list before Monday 5th.
This draft is based on the assumption that (again) the ripe-81++ stuff
will be reviewed by the Routing-WG (Jean-Michel?).
Could the NCC people please point me to the items that need a decision
in Lisbon (if any). I'd like to try for one more (and actually maybe
for the last time) to get a WG scheduling agreed that allows active
participation by a reasonable number of interested people to really
facilitate consensus and decisions...
Any feedback appreciated!
Wilfried.
--------------------------------------------------------------------------------
1st Draft -- 1st Draft -- 1st Draft
Draft agenda for the DB-Working-Group at RIPE-19, Lisbon.
---------------------------------------------------------
0. Opening (30')
. appointment of scribe
. amendment/rearrangement of agenda
. any admin stuff
. review of DB-WG in the context of a changing RIPE
x. The Classless Database (60')
. review of beta (as announced by Marten T.)
. review of requirements and scheduled changes
. document review (ripe-clarep, ripe-inetnum)
. discussion and decision
x. Database Operations Review (60')
. potential guardian mechanism changes
. RIPE-Handles
. any loose ends? (experiences)
. ownership of objects
and update responsibility and coordination (Daniel K.)
. need for new types of lookup/backlinks? (Havard E.)
x. Interworking with other regions (30')
. DB-Exchange (status)
. RWhois, aggrwalk, ...
x. CLNS Routing Registry (10')
. status review and decision about further activities
Z. AOB
--------------------------------------------------------------------------
Wilfried Woeber : e-mail: Wilfried.Woeber(a)CC.UniVie.ac.at
Computer Center - ACOnet :
Vienna University : Tel: +43 1 4065822 355
Universitaetsstrasse 7 : Fax: +43 1 4065822 170
A-1010 Vienna, Austria, Europe : NIC: WW144
--------------------------------------------------------------------------
3
2
Folks,
As you may have guessed, we have put quite some work over the last few
months into getting the RIPE database classless. We currently have a
beta implementation running, with the idea that we will switch to this
software shortly after the RIPE meeting.
We would like you to have a look at the whois server we currently have
running on my workstation rijp.ripe.net. If you have some time, please
fire off some queries to this machine to see if the server responds
like you would expect it to respond. A few things:
- the new server is slightly slower than the current one. This mainly
because of the classless lookups, and the fact that the database is no
longer kept in one file, but seperate files per object type, each with
their own index. Also the server uses data on a remote file system.
- although the server supports more and less specific lookups for
networks, the current client you may have will not support this. A new
client will be given out as soon as this has been properly tested at
the NCC.
- you can now specify network lookups of the forms:
192.87.45.1
192.87.45.1/32
ie host addresses are recognized, and prefix/length lookups are
recognized. The old style queries like "128.141" are still supported
as well.
- the default behaviour for network queries is that the server will
give an exact match if available or the first less specific match for
this query. So for host or subnet queries, the server will output the
classful network mostly.
- the test database is aligned with the real database for most of the
data. We have also put in quite some test data like the ripe-81 routes
and some inet-rtr objects. Please use this database only for testing,
not for authoritative output. Because we are still working on all
this, the new objects may sometimes show up and sometimes not.
- we have also generated objects for the class C blocks that we have
delegated to local IRs. So, for queries of non-assigned numbers, you
should get the class C block they come out of.
Basically we would like to get an idea from you that we have not
changed the look and feel of the server in a way that may cause tools
you may have that use the whois server to fail.
If you find any problems, please direct them to me personally.
Cheers,
-Marten
PS Please note you have to do:
whois -h rijp.ripe.net <query>
to get the new database software to respond.
1
0
Hi,
see the attached which contains my original question/suggestion and Tony's
response.
My main motivation for wanting this is to make it easier to see the
references when a subset of the database is presented (without having to
follow the nic-hdl cross-references). Such a superset might be an overview
of all the objects a given person is registered as contact (either admin-
or tech-) for. I have plans to make people more aware of the fact that
they are registered as contacts and their roles and responsibilities in
connection with this (e.g for the domain objects, where I have my own set
of roles and responsibilities I want to make them aware of).
I agree that what I am asking for is syntactic sugar, and that "pulling up"
the names instead of the NIC handles in the objects could be done by my
"database extraction" tool rather than having it implemented in the
database. I do however not think that I myself had the idea for the syntax
for the reference (in tech-c and admin-c), but I can't think of where I
have seen it suggested before.
This is merely to suggest the issue and not put too much pressure behind
it; I can take "no" for an answer.
Oh, yes, while on a bordering issue I probably should mention this
(although it is beginning to deviate from the main issue in this letter,
modify Subject line if you respond to this): The description of what kind
of roles and responsibilities the contact persons are supposed to have are
IMHO a bit imprecisely defined. This may be intentionally, but then again
it may not. I personally would be happy with a better clarification on
this point (I am referring to the descriptions in the documents ripe-50
etc., I'm sorry that I haven't kept track of whether the new database
documents are out yet).
- Havard
1
0
This is the promised summary of changes of document to help focus
discussion at the forthcoming RIPE meeting.
URL: ftp://ftp.ripe.net/ripe/drafts/ripe-81++.changes.txt -- Text version
URL: ftp://ftp.ripe.net/ripe/drafts/ripe-81++.changes.ps -- PS
version
--Tony.
Summary of changes in RIPE-81++ from previous RIPE
Meeting.
Tony Bates
23rd August, 1994
1. Introduction
In an effort to focus discussion for the forthcoming RIPE meeting in
Lisbon in September I have made a brief outline of the changes to
the RIPE-81++ draft from the last RIPE meeting. It is divided into
two sections; basic and major changes. The major changes section
will be most relevant for the forthcoming RIPE meeting and in par-
ticular the RIPE routing working group. The latest RIPE-81++ draft
is available from:
URL: ftp://ftp.ripe.net/ripe/drafts/ripe-81++.{ps,txt}
2. Basic Agreed Changes
This sections details the changes that were agreed and have been
fully incorporated into the current draft of RIPE-81++. All the
changes are with respect to the RIPE-81++ proposal tabled at the
RIPE meeting in Amsterdam in May, 1994. In each case only very brief
detail is given as these changes have been agreed by consensus.
Network Lists.
Add the use of network lists in the routing policy expression com-
ponent. This will be in the form proposed by Merit. i.e. list of
nets separate by commas within braces:
{ 35.0.0.0/8, 192.87.45.0/24 }
Extension to "default" attribute
There is a set of additional OPTIONAL components added to the
default attribute. See RIPE-81++ for more details.
- 2 -
Syntactic SUGAR
We added in the additional reserved words to make the syntax
clearer. NOTE: the reserved words will all be in lower-case to dis-
tinguish them from special policy keywords and communities.
Here is a summary of current SUGAR to add and where.
accept
announce
exclude
from
to
transit
Examples of the usage of the reserved words are:
as-in: from neighborAS accept route
as-out: to neighborAS announce route
as-exclude: exclude ASpath to destination
as-transit: transit ASpath to destination
default: from neighborAS accept route
default: to neighborAS announce route
Note: that as-transit is an experimental attribute. See below.
Network Representation
We used the "prefix length" notation documented in the classless
proposal paper. i.e.
35.0.0.0/8
192.87.45.0/24
"as-reject" changed to "as-exclude"
The text remained the same. The name of the attribute changed.
3. Major Changes
This section details the major changes with respect to the draft
- 3 -
presented at the RIPE meeting in Amsterdam in May, 1994.
The "component" attribute is gone
The component attribute was dropped as it was deemed to be too com-
plex to understand and too difficult to maintain and guard. The out-
come of this is two new attributes and one new object that facili-
tate the functionality of the component attribute
1) withdrawn attribute
Often is is useful to show a route that has been withdrawn from
the routing table. The has become very important now that CIDR
is deployed as service providers start to withdraw more
specific routes from an aggregate.
2) hole attribute
For tools in can be very useful to indicate "holes" in a CIDR
aggregate where there is currently no expected connectivity.
3) inet-rtr object
This allows you to detail the interfaces of a router as well as
the AS the router belong to. This is extremely useful for
routes/networks which fall into the category of what used to be
called "inter-as networks" described by the proposed to be
obsoleted "ias-int" attribute in the "inetnum" object. This
object is described in:
Bates, T., "Specifying an `Internet Router' in the Routing
Registry", July, 1994. DRAFT.
URL: ftp://ftp.ripe.net/drafts/inet-rtr.{ps,txt}
The "interas-in" and "interas-out" attributes.
This is an additional set of attributes added to detail local poli-
cies between any two ASes which have more than one interconnecting
link. This description is necessary only if the ASs are connected in
more than one way and the routing policy and differs at these two
connections.
Example:
LINK1
193.0.1.1 +----------+ 193.0.1.2
| |
AS1------AS2== ==AS3-----AS4
| |
193.0.1.5 +----------+ 193.0.1.6
LINK2
- 4 -
Descriptions of interas policies do not replace the global pol-
icy described in as-in, as-out and other policy attributes which
always describes the global policy between the two ASes. The
interas-in/out attributes only specify local variations to the glo-
bal policy described in the other attributes. If the global policy
mentions more routes than the local policy then local preferences
for these routes are assumed to be equal for all links.
A simple extendable syntax has been defined for this additional
information. For details of this refer to the ripe-81++ draft.
Possible outstanding issues with interas-in/interas-out
A major discussion point came from these attributes
The ordering
There were two styles of ordering proposed.
A) interas-in: <my id> [from] ASxx <neighbor id> <pref> <pol-
icy>
B) interas-in: [from] ASxxx <my id> <neighbor id> <pref> <pol-
icy>
Fortunately, an executive decision has been made by the chair
of the RIPE routing group to go with option B. The main reason
behind this is for consistency with the as-in and as-out attri-
butes.
Clarification of evaluation of operators.
Some text has been added to clarify the ordering of how the logical
operators are evaluated in routing policy expressions and what they
actually mean. It was recognised that ripe-81++ was weak on this
point.
This text is taken verbatim from the ripe-81++ draft:
.... <routing policy expression> can take the following formats.
1. A list of one or more ASes, AS Macros, Communities or Net-
work Lists.
A Network List is a list of network numbers in prefix
length format, separated by commas, and surrounded by
curly brackets (braces, i.e. `{' and '}').
Examples:
- 5 -
as-in: from AS1103 100 accept AS1103
as-in: from AS786 105 accept AS1103
as-in: from AS786 10 accept AS786 HEPNET
as-in: from AS1755 110 accept AS1103 AS786
as-in: from AS3333 100 accept {192.87.45.0/16, 128.141.0.0/16}
2. A set of KEYWORDS. The following KEYWORD is currently
defined:
ANY this means anything the neighbour AS knows.
3. A logical expression of either 1 or 2 above The current
logical operators are defined as:
AND
OR
NOT
This operators are defined as true BOOLEAN operators even
if the operands themselves do not appear to be BOOLEAN.
Their operations are defined as follows:
Operator Operation Example
OR UNION AS1 OR AS2
|
+-> all routes in AS1 or AS2.
AND INTERSECTION AS1 AND HEPNET
|
+-> a route in AS1 and belonging
to community HEPNET.
NOT COMPLEMENT NOT AS3
|
+-> any route except AS3 routes.
Rules are grouped together using parenthesis i.e "(" and
")".
The ordering of evaluation of operators and there associa-
tion is as follows:
Operator Associativity
() left to right
NOT right to left
AND left to right
OR left to right
- 6 -
NOTE: if no logical operator is given between ASes, AS-
macros, Communities, Network Lists and KEYWORDS it is
implicitly evaluated as an `OR' operation. The OR can be
left out for conciseness. However, please note the opera-
tors are still evaluated as below so make sure you include
parentheses whenever needed. To highlight this here is a
simple example. If we denoted a policy of for example;
from AS1755 I accept all routes except routes from AS1, A2
and AS3 and you enter the following as-in line.
as-in: from AS1755 100 accept NOT AS1 AS2 AS3
This will be evaluated as:
as-in: from AS1755 100 accept NOT AS1 OR AS2 OR AS3
Which in turn would be evaluated like this:
(NOT AS1) OR AS2 OR AS3
-> ((ANY except AS1) union AS2) union AS3)
--> (ANY except AS1)
This is clearly incorrect and not the desired result. The
correct syntax should be:
as-in: from AS1755 100 accept NOT (AS1 AS2 AS3)
Producing the following evaluation:
NOT (AS1 OR AS2 OR AS3)
-> (ANY) except (union of AS1, AS2, AS3)
Which depicts the desired routing policy.
Note that can also be written as below which is perhaps
somewhat clearer:
as-in: from AS1755 100 accept ANY AND NOT (AS1 OR AS2 OR AS3)
1
0
Unfortunately, a couple of small changes needed to be made to the
RIPE-81++ draft. The changes concern the semantics, ordering and
associativity of the logical operators defined for the routing policy
expression syntax. My thanks to Cengiz Alaettinoglu at ISI for
pointing this out to me. The other change was to make the local-rid and
remote-rid fields mandatory in the interas-in/interas-out attributes
to avoid ambiguity in the syntax. This I hope to be the last change
before the RIPE meeting.
The latest draft is available as:
URL ftp://ftp.ripe.net/ripe/drafts/ripe-81++.ps
URL ftp://ftp.ripe.net/ripe/drafts/ripe-81++.txt
I will not include a copy of the text this time ;-).
Please also note I will send a very brief summary of changes document
out on Friday to help focus discussion at the RIPE meeting.
--Tony.
1
0
Please find below the last draft of ripe-81++ to be issued before the
RIPE meeting. The changes are only slight but include some comments
from Kannan Varadhan sent direclty to me and a further slight
clarification to the interas-in/interas-out text as well as
the Table of Contents being updated to be correct. I intened to send
out a seperate `short' document summarising the major changes from the
last meeting and also highlighting any currently open issues to focus
the discussion at the forthcoming RIPE meeting.
As usual the draft is available as:
ftp://ftp.ripe.net/drafts/ripe-81++.{ps,txt}
Regards,
--Tony.
Representation of IP Routing Policies
in a Routing Registry
(ripe-81++)
DRAFT DRAFT DRAFT
Tony Bates
Elise Gerich
Laurent Joncheray
Jean-Michel Jouanigot
Daniel Karrenberg
Marten Terpstra
Jessica Yu
Document-ID: ripe-1nn
Obsoletes: ripe-81
August, 1994
ABSTRACT
This document is an update to the original `ripe-
81'[1] proposal for representing and storing routing
polices within the RIPE database. It incorporates
several extensions proposed by Merit Inc.[2] and gives
details of a generalised IP routing policy representa-
tion to be used by all Internet routing registries. It
acts as both tutorial and provides details of database
objects and attributes that use and make up a routing
registry.
ripe-1nn.txt August, 1994
- 2 -
Table of Contents
1 Introduction ................................................ 3
2 Organisation of this Document ............................... 3
3 General Representation of Policy Information ................ 4
4 The Routing Registry and the RIPE Database .................. 10
5 The Route Object ............................................ 14
6 The Autonomous System Object ................................ 23
7 The AS Macro Object ......................................... 30
8 The Community Object ........................................ 31
9 Representation of Routing Policies .......................... 34
10 Future Extensions .......................................... 43
11 References ................................................. 45
12 Authors Addresses .......................................... 46
Appendix A - Syntax for the "aut-num" object .................. 48
Appendix B - Syntax for the "community" object ................ 57
Appendix C - Syntax for the "as-macro" object ................. 61
Appendix D - Syntax for the "route" object .................... 65
Appendix E - List of reserved words ........................... 69
Appendix F - Motivations for RIPE-81++ ........................ 70
Appendix G - Transition strategy .............................. 72
ripe-1nn.txt August, 1994
- 3 -
1. Introduction
This document is a much revised version of the RIPE routing registry
document known as ripe-81[1]. Since its inception in February, 1993
and the establishment of the RIPE routing registry, several addi-
tions and clarifications have come to light which can be better
presented in a single updated document rather than separate addenda.
Some of the text remains the same the as the original ripe-81 docu-
ment keeping its tutorial style mixed with details of the RIPE data-
base objects relating to routing policy representation. However
this document does not repeat the background and historical remarks
in ripe-81. For these please refer to the original document. It
should be noted that whilst this document specifically references
the RIPE database and the RIPE routing registry one can easily read
"Regional routing registry" in place of RIPE as this representation
is certainly general and flexible enough to be used outside of the
RIPE community incorporating many ideas and features from other
routing registries in this update.
As you can see this document has a new RIPE document identification
number but can also be referred to as ripe-81++. Appendix F summar-
ises the changes from ripe-81 plus the motivation for these changes.
We would like to acknowledge many people for help with this docu-
ment. Specifically, Peter Lothberg who was a co-author of the ori-
ginal ripe-81 document for his many ideas and Gilles Farrache. We
would also like to thank the RIPE routing working group for their
review and comment. Finally, we like to thank Merit Inc. for many
constructive comments and ideas and making the routing registry a
worldwide Internet service. We would also like to acknowledge the
funding provided by the PRIDE project run in conjunction with the
RARE Technical Program, RIPE and the RIPE NCC without which this
paper would not have been possible.
2. Organisation of this Paper
This paper acts as both a basic tutorial for understanding routing
policy and provides details of objects and attributes used within an
Internet routing registry to store routing policies. Section 3
describes general issues about IP routing policies and their
representation in routing registries. Experienced readers may wish
to skip this section. Section 4 provides an overview of the RIPE
database, its basic concepts, schema and objects which make up the
database itself. It highlights the way in which the RIPE database
splits routing information from allocation information. Sections 5,
6, 7 and 8 detail all the objects associated with routing policy
representation. Section 9 gives a fairly extensive "walk through"
of how these objects are used for expressing routing policy and the
general principles behind their use. Section 10 provides a list of
references used throughout this document. Appendix A, B, C and D
document the formal syntax for the database objects and attributes.
Appendix F details the main changes from ripe-81 and motivations for
these changes. Appendix G tackles the issues of transition from
ripe-1nn.txt August, 1994
- 4 -
ripe-81 to ripe-81++.
ripe-1nn.txt August, 1994
- 5 -
3. General Representation of Policy Information
Networks, Network Operators and Autonomous Systems
Throughout this document an effort is made to be consistent with
terms so as not to confuse the reader.
When we talk about "networks" we mean physical networks which have a
unique classless IP network number: Layer 3 entities. We do not mean
organisations.
We call the organisations operating networks "network operators".
For the sake of the examples we divide network operators into two
categories: "service providers" and "customers". A "service pro-
vider" is a network operator who operates a network to provide
Internet services to different organisations, its "customers". The
distinction between service providers and customers is not clear
cut. A national research networking organisation frequently acts as
a service provider to Universities and other academic organisations,
but in most cases it buys international connectivity from another
service provider. A University networking department is a customer
of the research networking organisation but in turn may regard
University departments as its customers.
An Autonomous System (AS) is a group of IP networks having a single
clearly defined routing policy which is run by one or more network
operators. Inside ASes IP packets are routed using one or more Inte-
rior Routing Protocols (IGPs). In most cases interior routing deci-
sions are based on metrics derived from technical parameters like
topology, link speeds and load(1).
ASes exchange routing information with other ASes using Exterior
Routing Protocols (EGPs). Exterior routing decisions are frequently
based on policy based rules rather than purely on technical parame-
ters. Tools are needed to configure complex policies and to commun-
icate those policies between ASes while still ensuring proper opera-
tion of the Internet as a whole. Some EGPs like BGP-3 [8] and BGP-4
[9] provide tools to filter routing information according to policy
rules and more. None of them provides a mechanism to publish or com-
municate the policies themselves. Yet this is critical for opera-
tional coordination and fault isolation among network operators and
thus for the operation of the global Internet as a whole. This
document describes a "Routing Registry" providing this functional-
ity.
_________________________
(1) The entity we refer to as an AS is frequently and
more generally called a routing domain with the AS just
being an implementation vehicle. We have decided to use
the term AS exclusively because it relates more direct-
ly with the database objects and routing tools. By us-
ing only one term we hope to reduce the number of con-
cepts and to avoid confusion. The academically inclined
reader may forgive us.
ripe-1nn.txt August, 1994
- 6 -
Routing Policies
The exchange of routing information between ASes is subject to rout-
ing policies. Consider the case of two ASes, X and Y exchanging
routing information:
NET1 ...... ASX <---> ASY ....... NET2
ASX knows how to reach a network called NET1. It does not matter
whether NET1 is belonging to ASX or some other AS which exchanges
routing information with ASX either directly or indirectly; we just
assume that ASX knows how to direct packets towards NET1. Likewise
ASY knows how to reach NET2.
In order for traffic from NET2 to NET1 to flow between ASX and ASY,
ASX has to announce NET1 to ASY using an external routing protocol.
This states that ASX is willing to accept traffic directed to NET1
from ASY. Policy thus comes into play first in the decision of ASX
to announce NET1 to ASY.
In addition ASY has to accept this routing information and use it.
It is ASY's privilege to either use or disregard the information
that ASX is willing to accept traffic for NET1. ASY might decide not
to use this information if it does not want to send traffic to NET1
at all or if it considers another route more appropriate to reach
NET1.
So in order for traffic in the direction of NET1 to flow between ASX
and ASY, ASX must announce it to ASY and ASY must accept it from
ASX:
resulting packet flow towards NET1
<<===================================
|
|
announce NET1 | accept NET1
--------------> + ------------->
|
AS X | AS Y
|
<------------- + <--------------
accept NET2 | announce NET2
|
|
resulting packet flow towards NET2
===================================>>
Ideally, and seldom practically, the announcement and acceptance
policies of ASX and ASY are identical.
ripe-1nn.txt August, 1994
- 7 -
In order for traffic towards NET2 to flow, announcement and accep-
tance of NET2 must be in place the other way round. For almost all
applications connectivity in just one direction is not useful at
all.
It is important to realise that with current destination based for-
warding technology routing policies must eventually be expressed in
these terms. It is relatively easy to formulate reasonable policies
in very general terms which CANNOT be expressed in terms of announc-
ing and accepting networks. With current technology such policies
are almost always impossible to implement.
Usually policies are not configured for each network separately but
for groups of networks. In practise these groups are almost always
defined by the networks forming one or more ASes.
Routing Policy limitations
The generic example of a reasonable but un-implementable routing is
a split of already joined packet streams based on something other
than destination address. Once traffic for the same destination
network passes the same router, or the same AS at our level of
abstraction, it will take exactly the same route to the destina-
tion(2).
In a concrete example AS Z might be connected to the outside world
by two links. AS Z wishes to reserve these links for different
kinds of traffic, let's call them black and white traffic. For this
purpose the management of AS Z keeps two lists of ASes, the black
and the white list. Together these lists comprise all ASes in the
world reachable from AS Z.
"W"
<--->
... AS Z .... NET 3
<--->
"B"
It is quite possible to implement the policy for traffic originating
in AS Z: AS Z will only accept announcements for networks in white
ASes on the white link and will only accept announcements for net-
works in black ASes on the black link. This causes traffic from
networks within AS Z towards white ASes to use the white link and
likewise traffic for black ASes to use the black link.
Note that this way of implementing things makes it necessary to
decide on the colour of each new AS which appears before traffic can
be sent to it from AS Z. A way around this would be to accept only
_________________________
(2) Disregarding special cases like "type of service"
routing, load sharing and routing instabilities.
ripe-1nn.txt August, 1994
- 8 -
white announcements via the white link and to accept all but white
announcements on the black link. That way traffic from new ASes
would automatically be sent down the black link and AS Z management
would only need to keep the list of white ASes rather than two
lists.
Now for the unimplementable part of the policy. This concerns
traffic towards AS Z. Consider the following topology:
B AS ---) "W"
W AS ---) --->
B AS ---)>> AS A ---> ... AS Z .... NET 3
B AS ---) --->
W AS ---) "B"
As seen from AS Z there are both black and white ASes "behind" AS A.
Since ASes can make routing decisions based on destination only, AS
A and all ASes between AS A and the two links connecting AS Z can
only make the same decision for traffic directed at a network in AS
Z, say NET 3. This means that traffic from both black and white
ASes towards NET 3 will follow the same route once it passes through
AS A. This will either be the black or the white route depending on
the routing policies of AS A and all ASes between it and AS Z.
The important thing to note is that unless routing and forwarding
decisions can be made based on both source and destination
addresses, policies like the "black and white" example cannot be
implemented in general because "once joined means joined forever".
Access Policies
Access policies contrary to routing policies are not necessarily
defined in terms of ASes. The very simplest type of access policy is
to block packets from a specific network S from being forwarded to
another network D. A common example is when some inappropriate use
of resources on network D has been made from network S and the prob-
lem has not been resolved yet. Other examples of access policies
might be resources only accessible to networks belonging to a par-
ticular disciplinary group or community of interest. While most of
these policies are better implemented at the host or application
level, network level access policies do exist and are a source of
connectivity problems which are sometimes hard to diagnose. There-
fore they should also be documented in the routing registry accord-
ing to similar requirements as outlined above.
Routing vs. Allocation information
The RIPE database contains both routing registry and address space
allocation registry information. In the past the database schema
combined this information. Because RIPE was tasked with running both
an allocation and routing registry it seemed natural to initially
ripe-1nn.txt August, 1994
- 9 -
combine these functions. However, experience has shown that a clear
separation of routing information from allocation is desirable.
Often the maintainer of the routing information is not the same as
the maintainer of the allocation information. Moreover, in other
parts of the world there are different registries for each kind of
information.
Whilst the actual routing policy objects will be introduced in the
next section it is worthy of note that a transition from the current
objects will be required. Appendix G details the basic step of such
a transition.
This split in information represents a significant change in the
representational model of the RIPE database. Appendix F expands on
the reasons for this a little more.
Tools
The network operators will need a series of tools for policy rout-
ing. Some tools are already available to perform some of the tasks.
Most notably, the PRIDE tools [3] from the PRIDE project started in
September 1993 as well as others produced by Merit Inc [4] and CERN
[5].
These tools will enable them to use the routing policy stored in the
RIPE routing registry to perform such tasks as check actual routing
against policies defined, ensure consistency of policies set by dif-
ferent operators, and simulate the effects of policy changes.
Work continues on producing more useful tools to service the Inter-
net community.
ripe-1nn.txt August, 1994
- 10 -
4. The Routing Registry and the RIPE Database
One of the activities of RIPE is to maintain a database of Euro-
pean IP networks, DNS domains and their contact persons along with
various other kinds of network management information. The database
content is public and can be queried using the whois protocol as
well as retrieved as a whole. This supports NICs/NOCs all over
Europe and beyond to perform their respective tasks.
The RIPE database combines both allocation registry and routing
registry functions. The RIPE allocation registry contains data
about address space allocated to specific enterprises and/or
delegated to local registries as well as data about the domain name
space. The allocation registry is described in separate documents
[6,7] and outside the scope of this document.
Database Objects
Each object in the database describes a single entity in the real
world. This basic principle means that information about that
entity should only be represented in the corresponding data-
base object and not be repeated in other objects. The whois ser-
vice can automatically display referenced objects where appropriate.
The types of objects stored in the RIPE database are summarised in
the table below:
R Object Describes References
____________________________________________________________________
B person contact persons
A inetnum IP address space person
A domain DNS domain person
R aut-num autonomous system person
(aut-num,community)
R as-macro a group of autonomous systems person, aut-num
R community community person
R route a route being announced aut-num, community
R clns CLNS address space and routing person
The first column indicates whether the object is part of the alloca-
tion registry (A), the routing registry (R) or both (B). The last
column indicates the types of objects referenced by the particular
type of object. It can be seen that almost all objects reference
contact persons.
Objects are described by attributes value pairs, one per line.
Objects are separated by empty lines. An attribute that consists
ripe-1nn.txt August, 1994
- 11 -
of multiple lines should have the attribute name repeated on
consecutive lines. The information stored about network 192.87.45.0
consists of three objects, one inetnum object and two person
objects and looks like this:
inetnum: 192.87.45.0
netname: RIPE-NCC
descr: RIPE Network Coordination Centre
descr: Amsterdam, Netherlands
country: NL
admin-c: Daniel Karrenberg
tech-c: Marten Terpstra
rev-srv: ns.ripe.net
rev-srv: ns.eu.net
notify: ops(a)ripe.net
changed: tony(a)ripe.net 940110
source: RIPE
person: Daniel Karrenberg
address: RIPE Network Coordination Centre (NCC)
address: Kruislaan 409
address: NL-1098 SJ Amsterdam
address: Netherlands
phone: +31 20 592 5065
fax-no: +31 20 592 5090
e-mail: dfk(a)ripe.net
nic-hdl: DK58
changed: ripe-dbm(a)ripe.net 920826
source: RIPE
person: Marten Terpstra
address: RIPE Network Coordination Centre (NCC)
address: PRIDE Project
address: Kruislaan 409
address: NL-1098 SJ Amsterdam
address: Netherlands
phone: +31 20 592 5064
fax-no: +31 20 592 5090
e-mail: Marten.Terpstra(a)ripe.net
nic-hdl: MT2
notify: marten(a)ripe.net
changed: marten(a)ripe.net 931230
source: RIPE
Objects are stored and retrieved in this tag/value format. The RIPE
NCC does not provide differently formatted reports because any
desired format can easily be produced from this generic one.
ripe-1nn.txt August, 1994
- 12 -
Routing Registry Objects
The main objects comprising the routing registry are "aut-num" and
"route", describing an autonomous system and a route respectively.
It should be noted that routes not described in the routing registry
should never be routed in the Internet itself.
The autonomous system (aut-num) object provides contact information
for the AS and describes the routing policy of that AS. The routing
policy is described by enumerating all neighbouring ASes with which
routing information is exchanged. For each neighbour the routing
policy is described in terms of exactly what is being sent
(announced) and allowed in (accepted). It is important to note that
this is exactly the part of the global policy over which an AS has
direct control. Thus each aut-num object describes what can indeed
be implemented and enforced locally by the AS concerned. Combined
together all the aut-num objects provide the global routing graph
and permit to deduce the exact routing policy between any two ASes.
While the aut-num objects describe how routing information is pro-
pagated, the route object describes a single route injected into the
external routing mesh. The route object references the AS injecting
(originating) the route and thereby indirectly provides contact
information for the originating AS. This reference also provides the
primary way of grouping routes into larger collections. This is
necessary because describing routing policy on the level of single
routes would be awkward to impractical given the number of routes in
the Internet which is about 20,000 at the time of this writing.
Thus routing policy is most often defined for groups of routes by
originating AS. This method of grouping is well supported by
current exterior routing protocols. The route object also refer-
ences community objects described below to provide another method of
grouping routes. Modification of aut-num object itself and the
referencing by route objects is strictly protected to provide net-
work operators control over the routing policy description and the
routes originated by their ASes.
Sometimes even keeping track of groups of routes at the AS level is
cumbersome. Consider the case of policies described at the transit
provider level which apply transitively to all customers of the
transit provider. Therefore another level of grouping is provided by
the as-macro object which provides groups of ASes which can be
referenced in routing policies just like single ASes. Membership of
as-macro groups is also strictly controlled.
Sometimes there is a need to group routes on different criteria than
ASes for purposes like statistics or local access policies. This is
provided by the community object. A community object is much like
an AS but without a routing policy. It just describes a group of
routes. This is not supported at all by exterior routing protocols
and depending on aggregation of routes may not be generally usable
to define routing policies. It is suitable for local policies and
non-routing related purposes.
ripe-1nn.txt August, 1994
- 13 -
These routing related objects will be described in detail in the
sections below.
ripe-1nn.txt August, 1994
- 14 -
5. The Route Object
As stated in the previous chapter routing and address space alloca-
tion information are now clearly separated. This is performed with
the introduction of the route object. The route object will contain
all the information regarding a routing announcement.
All routing related attributes are removed from the inetnum object.
Some old attributes are obsoleted: connect, routpr-l, bdryg-l, nsf-
in, nsf-out, gateway). The currently useful routing attributes are
moved to the route object: aut-sys becomes origin, ias-int will be
encoded as part of the inet-rtr [15] object and comm-list simply
moves. See [6] for detail of the "inetnum" object definition.
The information in the old inetnum object
inetnum: 192.87.45.0
netname: RIPE-NCC
descr: RIPE Network Coordination Centre
descr: Amsterdam, Netherlands
country: NL
admin-c: Daniel Karrenberg
tech-c: Marten Terpstra
connect: RIPE NSF WCW
aut-sys: AS3333
comm-list: SURFNET
ias-int: 192.87.45.80 AS1104
ias-int: 192.87.45.6 AS2122
ias-int: 192.87.45.254 AS2600
rev-srv: ns.ripe.net
rev-srv: ns.eu.net
notify: ops(a)ripe.net
changed: tony(a)ripe.net 940110
source: RIPE
will be distributed over two objects:
ripe-1nn.txt August, 1994
- 15 -
inetnum: 192.87.45.0
netname: RIPE-NCC
descr: RIPE Network Coordination Centre
descr: Amsterdam, Netherlands
country: NL
admin-c: Daniel Karrenberg
tech-c: Marten Terpstra
rev-srv: ns.ripe.net
rev-srv: ns.eu.net
notify: ops(a)ripe.net
changed: tony(a)ripe.net 940110
source: RIPE
route: 192.87.45.0/24
descr: RIPE Network Coordination Centre
origin: AS3333
comm-list: SURFNET
changed: dfk(a)ripe.net 940427
source: RIPE
The route object is used to represent a single route originated into
the Internet routing mesh. The actual syntax is given in Appendix
D. However, there are several important aspects of the attributes
worthy of note.
The value of the route attribute will be a classless address. It
represents the exact route being injected into the routing mesh.
The representation of classless addresses is described in [10].
The value of the origin attribute will be an AS reference of the
form AS1234 referring to an aut-num object. It represents the AS
injecting this route into the routing mesh. The "aut-num" object
(see below) thus referenced provides all the contact information for
this route.
Special cases: There can only be a single originating AS in each
route object. However in todays Internet sometimes a route is
injected by more than one AS. This situation is potentially
dangerous as it can create conflicting routing policies for that
route and requires coordination between the originating ASes. In
the routing registry this is represented by multiple route objects.
This is a departure from the one route (net), one AS principle of
the ripe-81 routing registry. The consequences for the different
tools based in the routing registry will need to be evaluated and
possibly additional consistency checking of the database is needed.
ripe-1nn.txt August, 1994
- 16 -
The examples below will illustrate the usage of the route object
further. Suppose three chunks of address space of 2 different
enterprises represented by the following inetnum objects:
Examples
inetnum: 193.0.1.0
netname: ENT-1
descr: Enterprise 1
...
inetnum: 193.0.8.0
netname: ENT-2
descr: Enterprise 2
...
inetnum: 193.0.9.0
netname: ENT-2-SPEC
descr: Enterprise 2
...
Supposing that the Enterprises have their own AS numbers straight
application of routing without aggregation would yield:
route: 193.0.1.0/24
descr: Enterprise 1
origin: AS1
...
route: 193.0.8.0/24
descr: Enterprise 2
origin: AS2
...
route: 193.0.9.0/24
descr: Enterprise 2
origin: AS2
...
NB: This representation can be achieved by straight translation from
the ripe-81 representation. See Appendix G for more details.
Homogeneous Aggregation
The two chunks of address space of Enterprise 2 can be represented
by one aggregate route turning two route objects into one and poten-
tially saving routing table space for one route.
ripe-1nn.txt August, 1994
- 17 -
route: 193.0.8.0/23
descr: Enterprise 2
origin: AS2
...
Note that AS2 can also decide to originate all routes mentioned so
far, two 24-bit prefixes and one 23-bit prefix. This case would be
represented by storing all three route objects in the database. In
this particular example the additional routes will not add any func-
tionality however and only increase the amount of routes announced
unnecessarily.
Heterogeneous Aggregation
Consider the following case however:
route: 193.0.8.0/24
descr: Enterprise 2
origin: AS2
...
route: 193.0.9.0/24
descr: Enterprise 2 / Special
origin: AS2
comm-list: SPECIAL
...
Now the prefix 193.0.9.0/24 belongs to community SPECIAL (this com-
munity may well not be relevant to routing) and the other prefix
originated by AS2 does not. If AS2 aggregates these prefixes into
the 193.0.8.0/23 prefix, routing policies based on the community
value SPECIAL cannot be implemented in general, because there is no
way to distinguish between the special and the not-so-special parts
of AS2. If another AS has the policy to accept only routes to
members of community SPECIAL it cannot implement it, because accept-
ing the route to 193.0.8.0/23 would also route to 193.0.8.0/24 and
not accepting this route would lose connectivity to the special part
193.0.9.0/24. We call aggregate routes consisting of components
belonging to different communities or even different ASes "hetero-
geneous aggregates".
The problems introduced with heterogeneous aggregates are that once
the homogeneous routes are withdrawn one cannot tell if a more
specific part of the heterogeneous has a different policy. However,
if can be counter argued that knowing this policy is of little use
if you cannot implement a routing policy based on the less specific
(and only route present) heterogeneous aggregate. In fact, this
displays a facet of CIDR itself in that one may actually compromise
slight variations on policy over announcing a larger (albeit
ripe-1nn.txt August, 1994
- 18 -
heterogeneous in terms of policy) aggregate to save address space.
However, it is still useful to be able to document these variations
in policy especially when this homogeneous more specific route is
just being withdrawn. For this one can use the "withdrawn" attri-
bute. The withdrawn attribute can serve to both indicate that a less
specific aggregate is in fact heterogeneous and also allow the gen-
eral documenting of route withdrawal.
So there has to be a way for AS2 to document this even if it does
not originate the route to 193.0.9.0/24 any more. This can be done
with the "withdrawn" attribute of the route object. The aggregate
route to 193.0.8.0/23 is now be registered as:
route: 193.0.8.0/23
descr: Enterprise 2
origin: AS2
...
With the two homogeneous routes marked as withdrawn from the Inter-
net routing mesh but still preserving their original routing infor-
mation.
route: 193.0.8.0/24
descr: Enterprise 2
origin: AS2
withdrawn: 940701
...
route: 193.0.9.0/24
descr: Enterprise 2 / Special
origin: AS2
comm-list: SPECIAL
withdrawn: 940701
...
It should be noted that the date value used in the withdrawn attri-
bute can only be in the past.
Proxy Aggregation
The next step of aggregation are aggregates consisting of more than
one AS. This generally means one AS is aggregating on behalf of
another. It is called proxy aggregation. Proxy aggregation should be
done with great care and always be coordinated with other providers
announcing the same route.
Consider the following:
ripe-1nn.txt August, 1994
- 19 -
route: 193.0.0.0/20
descr: All routes known by AS1 in a single package
origin: AS1
...
route: 193.0.1.0/24
descr: Foo
origin: AS1
withdrawn: 940310
...
route: 193.0.8.0/24
descr: Bar
origin: AS2
withdrawn: 940310
...
route: 193.0.9.0/24
descr: Bar-2
origin: AS2
withdrawn: 940310
comm-list: SPECIAL
...
If AS1 announced no other routes to a single homed neighbouring AS,
that neighbour can in general either take that route or leave it but
not differentiate between AS1 and AS2.
Note: If the neighbor was previously configured to accept routes
originating in AS2 but not in AS1 they lose connectivity to AS2 as
well. This means that proxy aggregation has to be done carefully
and in a well coordinated fashion. The information in the withdrawn
route object can help to achieve that.
Aggregates with Holes
If we assume that the world of our example still consists of only
three chunks of address space the aggregate above contains what are
called holes, parts of an aggregate that are not reachable via the
originator of the route. From the routing information itself one
cannot tell whether these are holes and what part of the route falls
inside one. The only way to tell is to send a packet there and see
ripe-1nn.txt August, 1994
- 20 -
whether it gets to the destination, or an ICMP message is received
back, or there is silence. On the other hand announcing aggregates
with holes is quite legitimate. Consider a 16-bit aggregate with
only one 24-bit prefix unreachable. The savings in routing table
size by far outweigh the hole problem.
For operational reasons however it is very useful to register these
holes in the routing registry. Consider the case where a remote net-
work operator experiences connectivity problems to addresses inside
an aggregate route. If the packets are getting to the AS announcing
the aggregate and there are no more specific routes, the normal
cause of action is to get in touch with the originating AS of the
aggregate route and ask them to fix the problem. If the address
falls into a hole this is futile. Therefore problem diagnosis can be
sped up and unnecessary calls prevented by registering the holes in
the routing registry. We do this by using the "hole" attribute. In
our example the representation would be:
route: 193.0.0.0/20
descr: All routes known by AS1
origin: AS1
hole: 193.0.0.0/24
hole: 193.0.2.0/23
hole: 193.0.4.0/22
hole: 193.0.10.0/23
hole: 193.0.12.0/22
...
Note: there would also be two routes with the withdrawn attribute as
displayed above (i.e. 193.0.8.0/24 and 193.0.9.0/24)
Multiple Proxy Aggregation
Finally suppose that AS2 decides to announce the same aggregate,
they would add the following route object to the registry:
route: 193.0.0.0/20
descr: All routes known by AS2
origin: AS2
hole: 193.0.0.0/24
hole: 193.0.2.0/23
hole: 193.0.4.0/22
hole: 193.0.10.0/23
hole: 193.0.12.0/22
...
As per the update procedures below both AS1 and AS2 will be notified
that there already is a route to the same prefix in the registry.
This multiple proxy aggregation is very dangerous to do if the sub-
ripe-1nn.txt August, 1994
- 21 -
aggregates of the route are not the same. It is still dangerous when
the sub-aggregates are consistent but connectivity to the sub-
aggregates varies widely between the originators.
Route object update procedures
Adding a route object will be have to be authorised by the guardian
of the originating AS. The actual implementation of this is outside
the scope of this document. This guarantees that an AS guardian has
full control over the registration of the routes it announces.
What is an Inter-AS network ?
An inter-AS network(3) exists for the purpose of passing traffic and
routing information between different autonomous systems. The most
simple example of an inter-AS network is a point-to-point link, con-
necting exactly two ASes. Each end of such a link is connected to
an interface of router belonging to each of the autonomous systems.
More complex examples are broadcast type networks with multiple
interfaces connecting multiple ASes with the possibility of more
than one connection per AS. Consider the following example of three
routers 1, 2 and 3 with interfaces a through f connected by two
inter-AS networks X and Y:
X Y
a1b --- c2d --- e3f
Suppose that network X is registered in the routing registry as part
of AS1 and net Y as part of AS3. If traffic passes from left to
right prtraceroute will report the following sequence of interfaces
and ASes:
a in AS1
c in AS1
e in AS3
The traceroute algorithm enumerates only the receiving interfaces on
the way to the destination. In the example this leads to the pas-
sage of AS2 going unnoticed. This is confusing to the user and will
also generate exceptions when the path found is checked against the
routing registry.
_________________________
(3) Inter-AS IP networks are those networks are
currently called FIXes, IXFs, DMZs, NAPs, GIX and many
other acronyms.
ripe-1nn.txt August, 1994
- 22 -
For operational monitoring tools such as prtraceroute it is neces-
sary to know which interface on an inter-AS network belongs to which
AS. If AS information is not known about interfaces on an inter-AS
network, tools like prtraceroute cannot determine correctly which
ASes are being traversed.
All interfaces on inter-AS networks will are described in a separate
object know as the `inet-rtr' object [15].
ripe-1nn.txt August, 1994
- 23 -
6. The Autonomous System Object
Autonomous Systems
An Autonomous System (AS) is a group of IP networks run by one or
more network operators which has a single and clearly defined rout-
ing policy.
An AS has a unique number associated with it which is used both in
exchange of exterior routing information and as an identifier of the
AS itself. Exterior routing protocols such as BGP and EGP are used
to exchange routing information between ASes.
In routing terms an AS will normally use one or more interior gate-
way protocols (IGPs) in conjunction with some sort of common agreed
metrics when exchanging network information within its own AS.
The term AS is often confused or even misused as a convenient way of
grouping together a set of networks which belong under the same
administrative umbrella even if within that group of networks there
are various different routing policies. We provide the "community"
concept for such use. ASes can strictly have only one single rout-
ing policy.
The creation of an AS should be done in a conscious and well coordi-
nated manner to avoid creating ASes for the sake of it, perhaps
resulting in the worst case scenario of one AS per routing announce-
ment. It should be noted that there is a limited number of AS
numbers available. Also creating an AS may well increase the number
of AS paths modern EGPs will have to keep track of. This aggravates
what is known as "the routing table growth problem". This may mean
that by applying the general rules for the creation and allocation
of an AS below, some re-engineering may well be needed. However,
this may be the only way to actually implement the desired routing
policy anyway. The creation and allocation of an AS should be done
with the following recommendations in mind:
o Creation of an AS is only required when exchanging routing
information with other ASes. Some router implementations make
use of an AS number as a form of tagging to identify the rout-
ing process. However, it should be noted that this tag does
not need to be unique unless routing information is indeed
exchanged with other ASes.
o For a simple case of customer networks connected to a single
service provider, the IP network should normally be a member of
the service providers AS. In terms of routing policy the IP
network has exactly the same policy as the service provider and
there is no need to make any distinction in routing informa-
tion. This idea may at first seem slightly alien to some, but
it highlights the clear distinction in the use of the AS number
ripe-1nn.txt August, 1994
- 24 -
as a representation of routing policy as opposed to some form
of administrative use.
o If a network operator connects to more than one AS with dif-
ferent routing policies then they need to create their own AS.
In the case of multi-homed customer networks connected to two
service providers there are at least two different routing pol-
icies to a given customer network. At this point the customer
networks will be part of a single AS and this AS would be dis-
tinct from either of the service providers ASes. This allows
the customer the ability of having a different representation
of policy and preference to the different service providers.
This is the ONLY case where a network operator should create
its own AS number.
o As a general rule one should always try to populate the AS with
as many routes as possible, providing all routes conform to the
same routing policy.
Each AS is represented in the RIPE database by both an AS object and
the route objects representing the routes originated by the AS. The
AS object stores descriptive, administrative and contact information
about the AS as well as the routing policies of the AS in relation
to all neighbouring ASes.
The origin attributes of the route objects define the set of routes
originated by the AS. Each route object can have exactly one origin
attribute. Route objects can only be created and updated by the
"guardian" of the AS and not by those immediately responsible for
the particular routes referenced therein. This ensures that opera-
tors, especially service providers, remain in control of AS routing
announcements.
The AS object itself is used to represent a description of adminis-
trative details and the routing policies of the AS itself. The AS
object definition is depicted as follows.
ripe-1nn.txt August, 1994
- 25 -
Example:
aut-num: AS1104
descr: NIKHEF-H Autonomous system
as-in: from AS1213 100 accept AS1213
as-in: from AS1913 100 accept AS1913
as-in: from AS1755 150 accept ANY
as-out: to AS1213 announce ANY
as-out: to AS1913 announce ANY
as-out: to AS1755 announce AS1104 AS1913 AS1213
tech-c: Rob Blokzijl
admin-c: Eric Wassenaar
guardian: as-guardian(a)nikhef.nl
changed: ripe-dbm(a)ripe.net 920910
source: RIPE
See Appendix A for a complete syntax definition of the "aut-num"
object.
It should be noted that this representation provides two things:
o a set of routes.
o a description of administrative details and routing policies.
The set of routes can be used to generate network list based confi-
guration information as well as configuration information for exte-
rior routing protocols knowing about ASes. This means an AS can be
defined and is useful even if it does not use routing protocols
which know about the AS concept.
ripe-1nn.txt August, 1994
- 26 -
Description of routing policies between ASs with multiple connec-
tions - "interas-in/interas-out"
Description of multiple connections between ASs defines how two ASs
have chosen to set different policies for the use of each or some of
the connections between the ASs. This description is necessary only
if the ASs are connected in more than one way and the routing policy
and differs at these two connections.
Example:
LINK1
193.0.1.1 +----------+ 193.0.1.2
| |
AS1------AS2== ==AS3-----AS4
| |
193.0.1.5 +----------+ 193.0.1.6
LINK2
Note: LINK here denotes to connection points between ASs.
It is not necessary just a serial link as it may be inter-
preted. It could be ethernet or other type of connection
as well.
It may be that AS2 wants to use LINK2 only for traffic towards AS4.
LINK1 is used for traffic to AS3 and as backup to AS4, should LINK2
fail. To implement this policy, one would use the attribute
"interas-in" and "interas-out." This attribute permits ASs to
describe their local decisions based on its preference such as
multi-exit-discriminators (MEDs) as used in some inter-domain rout-
ing protocols (BGP4, IDRP) and to communicate those routing deci-
sions. This information would be useful in resolving problems when
some traffic paths changed from traversing AS3's gateway in Timbuktu
rather than the gateway in Mogadishu. The exact syntax is given in
Appendix A. However, if we follow this example through in
terms of AS2 we would represent this policy as follows:
Example:
aut-num: AS2
as-in: from AS3 10 accept AS3 AS4
as-out: to AS3 announce AS1 AS2
interas-in: from AS3 193.0.1.1/32 193.0.1.2/32 (pref=5) accept AS3
interas-in: from AS3 193.0.1.1/32 193.0.1.2/32 (pref=15) accept AS4
interas-in: from AS3 193.0.1.5/32 193.0.1.6/32 (pref=10) accept AS4
...
ripe-1nn.txt August, 1994
- 27 -
Here we see additional policy information between two ASs in terms
of the IP addresses of the connection. The parentheses and keyword
are syntactic placeholders to add the readability of the attributes.
If pref=MED is specified the preference indicated by the remote AS
via the multi-exit- discriminator metric such as BGP is used. Of
course this type on inter-AS policy should always be bilaterally
agreed upon to avoid asymmetry and in practice there may need to be
corresponding interas-in attributes in the policy representation of
AS3.
The interas-out attribute is similar in the same way to interas-in
as as-out to as-in. The one major difference being that interas-out
allows to associate an outgoing metric with each route. It is impor-
tant to note that this metric is just passed to the peer AS and it
is at the peer AS's discretion to use or ignore it. A special value
of IGP specifies that the metric passed to the receiving AS will be
derived from the IGP of the sending AS. In this way the peer AS can
choose the optimal link for its traffic as determined by the sending
AS.
Descriptions of interas policies do not replace the global pol-
icy described in as-in, as-out and other policy attributes which
should be specified too. If the global policy mentions more
routes than the local policy then local preferences for these
routes are assumed to be equal for all links.
Any route specified in interas-in/out but not specified in as-in/out
is assumed not accepted/announced between the ASes concerned. Diag-
nostic tools should flag this inconsistency as an error.
ripe-1nn.txt August, 1994
- 28 -
How to describe the exclusion policy of a certain AS - "as-exclude"
Some ASes have a routing policy based on the exclusion of certain
routes if for whatever reason a certain AS is used as transit.
Whilst, this is in general not good practice as it makes implicit
assumptions on topology with asymmetry a possible outcome if not
coordinated, this case needs to be accommodated within the routing
policy representation.
The way this is achieved is by making use of the "as-exclude" attri-
bute. The precise syntax of this attribute can be found in Appendix
A along with the rest of the defined syntax for the "aut-num"
object. However, some explanation of the use of this attribute is
useful. If we have the following example topology.
Example:
AS4--------AS3
| | |
| | |
AS1--------AS2--------AS5
With a simple corresponding policy like so:
Example:
aut-num: AS1
as-in: from AS2 100 accept ANY
as-out: to AS2 announce AS1
as-exclude: exclude AS4 to ANY
....
We see an interesting policy. What this says in simple terms is AS1
doesn't want to reach anything if it transits AS4. This can be a
perfectly valid policy. However, it should be realised that if for
whatever reason AS2 decides to route to AS3 via AS4 then immediately
AS1 has no connectivity to AS3 or if AS1 is running default to AS2
packets from AS1 will still flow via AS4. The important point about
this is that whilst AS1 can advise its neighbours of its policy it
has no direct control on how it can enforce this policy to neigh-
bours upstream.
Another interesting scenario to highlight the unexpected result of
using such an "as-exclude" policy. If we assume in the above example
AS2 preferred AS4 to reach AS3 and AS1 did not use default routing
then as stated AS1 would have no connectivity to AS3. Now lets sup-
pose that for example the link between AS2 and AS4 went down for
some reason. Like so:
ripe-1nn.txt August, 1994
- 29 -
Example:
AS4--------AS3
|
|
AS1--------AS2--------AS5
Suddenly AS1 now has connectivity to AS3. This unexpected behavior
should be considered when created policies based on the "as-exclude"
attribute.
The second problem with this type of policy is the potential of
asymmetry. In the original example we saw the correct policy from
AS1's point of view but if ASes with connectivity through AS4 do not
use a similar policy you have asymmetric traffic and policy. If an
AS uses such a policy they must be aware of the consequences of its
use. Namely that the specified routes which transit the AS (i.e.
routing announcements with this AS in the AS path information) in
question will be excluded. If not coordinated this can easily cause
asymmetry or even worse loss of connectivity to unknown ASes behind
(or in front for that matter) the transit AS in question. With this
in mind this attribute can only be viewed as a form of advisory to
other service providers. However, this does not preclude its use
with policy based tools if the attribute exists.
By having the ability to specify a route keyword based on any of the
four notations given in the syntax it allows the receiving AS to
specify what routes it wishes to exclude through a given transit AS
to a network granularity.
ripe-1nn.txt August, 1994
- 30 -
7. AS Macros
It may be difficult to keep track of each and every new AS that is
represented in the routing registry. A convenient way around this
is to define an `AS Macro' which essentially is a convenient way to
group ASes. This is done so that each and every AS guardian does not
have to add a new AS to it's routing policy as described by the as-
in and as-out attributes of it's AS object.
However, it should be noted that this creates an implicit trust on
the guardian of the AS-Macro.
An AS-Macro can be used in <routing policy expressions> for the
"as-in" and "as-out" attributes in the aut-num object. The AS-Macro
object is then used to derive the list or group of ASes.
A simple example would be something like:
Example:
aut-num: AS786
as-in: from AS1755 100 accept AS-EBONE AND NOT AS1104
as-in: from AS1755 100 accept AS-EBONE AND NOT AS1104
as-out to AS1755 announce AS786
.....
Where the as-macro object for AS-EBONE is as follows:
as-macro: AS-EBONE
descr: ASes routed by EBONE
as-list: AS2121 AS1104 AS2600 AS2122
as-list: AS1103 AS1755 AS2043
guardian: guardian(a)ebone.net
......
So the policy would be evaluated to:
aut-num: AS786
as-in: from AS1755 100 accept (AS2121 OR AS1104 OR AS2600 OR AS2122
as-in: from AS1755 100 accept AS1103 OR AS1755 OR AS2043) AND NOT AS1104
......
It should be noted that the above examples incorporates the rule for
line wrapping as defined in Appendix A for policy lines. See Appen-
dix C for a definition on the AS-Macro syntax.
ripe-1nn.txt August, 1994
- 31 -
8. The Community Object
A community is a group of routes that cannot be represented by an AS
or a group of ASes. It is in some circumstances useful to define a
group of routes that have something in common. This could be a spe-
cial access policy to a supercomputer centre, a group of routes used
for a specific mission, or a disciplinary group that is scattered
among several autonomous systems. Also these communities could be
useful to group routes for the purpose of network statistics.
Communities do not exchange routing information, since they do not
represent an autonomous system. More specifically, communities do
not define routing policies, but access or usage policies. However,
they can de used as in conjunction with an ASes routing policy to
define a set of routes the AS sets routing policy for.
Communities should be defined in a strict manner, to avoid creating
as many communities as there are routes, or even worse. Communities
should be defined following the two rules below;
o Communities must have a global meaning. Communities that have
no global meaning, are used only in a local environment and
should be avoided.
o Communities must not be defined to express non-local policies.
It should be avoided that a community is created because some
other organisation forces a policy upon your organisation.
Communities must only be defined to express a policy defined by
your organisation.
Community examples
There are some clear examples of communities:
BACKBONE -
all customers of a given backbone service provider even though
they can have various different routing policies and hence
belong to different ASes. This would be extremely useful for
statistics collection.
HEPNET -
the High Energy Physics community partly shares infrastructure
with other organisations, and the institutes it consists of are
scattered all over Europe, often being part of a non HEPNET
autonomous system. To allow statistics, access or part of a
routing policy , a community HEPNET, consisting of all routes
that are part of HEPNET, conveniently groups all these routes.
ripe-1nn.txt August, 1994
- 32 -
NSFNET -
the National Science Foundation Network imposes an acceptable
use policy on routes that wish to make use of it. A community
NSFNET could imply the set of routes that comply with this pol-
icy.
MULTI -
a large multinational corporation that does not have its own
internal infrastructure, but connects to the various parts of
its organisations by using local service providers that connect
them all together, may decide to define a community to restrict
access to their networks, only by networks that are part of
this community. This way a corporate network could be defined
on shared infrastructure. Also, this community could be used by
any of the service providers to do statistics for the whole of
the corporation, for instance to do topology or bandwidth plan-
ning.
Similar to Autonomous systems, each community is represented in the
RIPE database by both a community object and community tags on the
route objects representing the routes belonging to the community.
The community object stores descriptive, administrative and contact
information about the community.
The community tags on the route objects define the set of routes
belonging to a community. A route can have multiple community tags.
The community tags can only be created and updated by the "guardian"
of the community and not by those directly responsible for the par-
ticular network. This ensures that community guardians remain in
control of community membership.
Here's an example of how this might be represented in terms of the
community tags within the network object. We have an example where
the route 192.16.199.0/24 has a single routing policy (i.e. that of
AS 1104), but is part of several different communities of interest.
We use the tag "comm-list" to represent the list of communities
associated with this route. NIKHEF-H uses the service provider
SURFNET (a service provider with customers with more than one rout-
ing policy), is also part of the High Energy Physics community as
well as having the ability to access the Supercomputer at CERN(4).
_________________________
(4) The community `CERN-SUPER', is somewhat national,
but is intended as an example of a possible use of an
access policy constraint.
ripe-1nn.txt August, 1994
- 33 -
Example:
route: 192.16.199.0/24
descr: Local Ethernet
descr: NIKHEF section H
origin: AS1104
comm-list: HEPNET CERN-SUPER SURFNET
changed: ripe-dbm(a)ripe.net 920604
source: RIPE
In the above examples some communities have been defined. The com-
munity object itself will take the following format:
Example:
community: SURFNET
descr: Dutch academic research network
authority: SURFnet B.V.
guardian: comm-guardian(a)surfnet.nl
admin-c: Erik-Jan Bos
tech-c: Erik-Jan Bos
changed: ripe-dbm(a)ripe.net 920604
source: RIPE
For a complete explanation of the syntax please refer to Appendix B.
ripe-1nn.txt August, 1994
- 34 -
9. Representation of Routing Policies
Routing policies of an AS are represented in the autonomous system
object. Initially we show some examples, so the reader is familiar
with the concept of how routing information is represented, used and
derived. Refer to Appendix A, for the full syntax of the "aut-num"
object.
The topology of routing exchanges is represented by listing how
routing information is exchanged with each neighbouring AS. This is
done separately for both incoming and outgoing routing information.
In order to provide backup and back door paths a relative cost is
associated with incoming routing information.
Example 1:
AS1------AS2
This specifies a simple routing exchange of two presumably isolated
ASes. Even if either of them has routing information about routes
in ASes other than AS1 and AS2, none of that will be announced to
the other.
aut-num: AS1
as-out: to AS2 announce AS1
as-in: from AS2 100 accept AS2
aut-num: AS2
as-out: to AS1 announce AS2
as-in: from AS1 100 accept AS1
The number 100 in the in-bound specifications is a relative cost,
which is used for backup and back door routes. The absolute value is
of no significance. The relation between different values within the
same AS object is. A lower value means a lower cost. This is cons-
ciously similar to the cost based preference scheme used with DNS MX
RRs.
Example 2:
Now suppose that AS2 is connected to one more AS, besides AS1, and
let's call that AS3:
AS1------AS2------AS3
ripe-1nn.txt August, 1994
- 35 -
In this case there are two reasonable routing policies:
a) AS2 just wants to exchange traffic with both AS1 and AS3 itself
without passing traffic between AS1 and AS3.
b) AS2 is willing to pass traffic between AS3 and AS1, thus acting
as a transit AS
Example 2a:
In the first case AS1's representation in the routing registry will
remain unchanged as will be the part of AS2's representation
describing the routing exchange with AS1. A description of the addi-
tional routing exchange with AS3 will be added to AS2's representa-
tion:
aut-num: AS1
as-out: to AS2 announce AS1
as-in: from AS2 100 accept AS2
aut-num: AS2
as-out: to AS1 announce AS2
as-in: from AS1 100 accept AS1
as-out: to AS3 announce AS2
as-in: from AS3 100 accept AS3
aut-num: AS3
as-out: to AS2 announce AS3
as-in: from AS2 100 accept AS2
Note that in this example, AS2 keeps full control over its
resources. Even if AS3 and AS1 were to allow each others routes in
from AS2, the routing information would not flow because AS2 is not
announcing it(5).
Example 2b:
If contrary to the previous case, AS1 and AS3 are supposed to have
connectivity to each other via AS2, all AS objects have to change:
_________________________
(5) Of course AS1 and AS3 could just send traffic to
each other to AS2 even without AS2 announcing the
routes, hoping that AS2 will forward it correctly. Such
questionable practices however are beyond the scope of
this document.
ripe-1nn.txt August, 1994
- 36 -
aut-num: AS1
as-out: to AS2 announce AS1
as-in: from AS2 100 accept AS2 AS3
aut-num: AS2
as-out: to AS1 announce AS2 AS3
as-in: from AS1 100 accept AS1
as-out: to AS3 announce AS2 AS1
as-in: from AS3 100 accept AS3
aut-num: AS3
as-out: to AS2 announce AS3
as-in: from AS2 100 accept AS1 AS2
Note that the amount of routing information exchanged with a neigh-
bour AS is defined in terms of routes belonging to ASes. In BGP
terms this is the AS where the routing information originates and
the originating AS information carried in BGP could be used to
implement the desired policy. However, using BGP or the BGP AS-path
information is not required to implement the policies thus speci-
fied. Configurations based on route lists can easily be generated
from the database. The AS path information, provided by BGP can
then be used as an additional checking tool as desired.
The specification understands one special expression and this can be
expressed as a boolean expressions:
ANY - means any routing information known. For output this means
that all routes an AS knows about are announced. For input it
means that anything is accepted from the neighbour AS.
ripe-1nn.txt August, 1994
- 37 -
Example 3:
AS4 is a stub customer AS, which only talks to service provider
AS123.
|
|
-----AS123------AS4
|
|
aut-num: AS4
as-out: to AS123 announce AS4
as-in: from AS123 100 accept ANY
aut-num: AS123
as-in: from AS4 100 accept AS4
as-out: to AS4 announce ANY
<further neighbours>
Since AS4 has no other way to reach the outside world than AS123 it
is not strictly necessary for AS123 to send routing information to
AS4. AS4 can simply send all traffic for which it has no explicit
routing information to AS123 by default. This strategy is called
default routing. It is expressed in the routing registry by adding
one or more default tags to the autonomous system which uses this
strategy. In the example above this would look like:
aut-num: AS4
as-out: to AS123 announce AS4
default: AS123 100
aut-num: AS123
as-in: from AS4 100 accept AS4
<further neighbours>
ripe-1nn.txt August, 1994
- 38 -
Example 4:
AS4 now connects to a different operator, AS5. AS5 uses AS123 for
outside connectivity but has itself no direct connection to AS123.
AS5 traffic to and from AS123 thus has to pass AS4. AS4 agrees to
act as a transit AS for this traffic.
|
|
-----AS123------AS4-------AS5
|
|
aut-num: AS4
as-out: to AS123 announce AS4 AS5
as-in: from AS123 100 accept ANY
as-out: to AS5 announce ANY
as-in: from AS5 50 accept AS5
aut-num: AS5
as-in: from AS4 100 accept ANY
as-out: to AS4 announce AS5
aut-num: AS123
as-in: from AS4 100 accept AS4 AS5
as-out: to AS4 announce ANY
<further neighbours>
Now AS4 has two sources of external routing information. AS5 which
provides only information about its own routes and AS123 which pro-
vides information about the external world. Note that AS4 accepts
information about AS5 from both AS123 and AS5 although AS5 informa-
tion cannot come from AS123 since AS5 is connected only via AS4
itself. The lower cost of 50 for the announcement from AS5 itself
compared to 100 from AS123 ensures that AS5 is still believed even
in case AS123 will unexpectedly announce AS5.
In this example too, default routing can be used by AS5 much like in
the previous example. AS4 can also use default routing towards
AS123:
ripe-1nn.txt August, 1994
- 39 -
aut-num: AS4
as-out: to AS123 announce AS4 AS5
default: AS123 11
as-in: from AS5 50 accept AS5
Note no announcements to AS5, they default to us.
aut-num: AS5
as-out: to AS4 announce AS5
default: AS4 100
aut-num: AS123
as-in: from AS4 100 announce AS4 AS5
<further neighbours>
Note that the relative cost associated with default routing is
totally separate from the relative cost associated with in-bound
announcements. The default route will never be taken if an explicit
route is known to the destination. Thus an explicit route can never
have a higher cost than the default route. The relative cost asso-
ciated with the default route is only useful in those cases where
one wants to configure multiple default routes for redundancy.
Note also that in this example the configuration using default
routes has a subtly different behavior than the one with explicit
routes: In case the AS4-AS5 link fails AS4 will send traffic to AS5
to AS123 when using the default configuration. Normally this makes
not much difference as there will be no answer and thus little
traffic. With certain datagram applications which do not require
acknowledgments however, significant amounts of traffic may be use-
lessly directed at AS123. Similarly default routing should not be
used if there are stringent security policies which proscribe any
traffic intended for AS5 to ever touch AS123.
Generally it can be said that default routing should only be used in
very simple topologies. Once the situation gets more complex using
default routes can lead to unexpected results or even defeat the
routing policies established when links fail. As an example consider
how Example 5a) below could be implemented using default routing.
ripe-1nn.txt August, 1994
- 40 -
Example 5:
In a different example AS4 has a private connection to AS6 which in
turn is connected to the service provider AS123:
|
|
-----AS123------AS4
| |
| |
| |
AS6 ---------+
There are a number of policies worth examining in this case:
a) AS4 and AS6 wish to exchange traffic between themselves
exclusively via the private link between themselves; such
traffic should never pass through the backbone (AS123). The
link should never be used for transit traffic, i.e. traffic not
both originating in and destined for AS4 and AS6.
b) AS4 and AS6 wish to exchange traffic between themselves via the
private link between themselves. Should the link fail, traffic
between AS4 and AS6 should be routed via AS123. The link
should never be used for transit traffic.
c) AS4 and AS6 wish to exchange traffic between themselves via the
private link between themselves. Should the link fail, traffic
between AS4 and AS6 should be routed via AS123. Should the
connection between AS4 and AS123 fail, traffic from AS4 to des-
tinations behind AS123 can pass through the private link and
AS6's connection to AS123.
d) AS4 and AS6 wish to exchange traffic between themselves via the
private link between themselves. Should the link fail, traffic
between AS4 and AS6 should be routed via AS123. Should the
backbone connection of either AS4 or AS6 fail, the traffic of
the disconnected AS should flow via the other AS's backbone
connection.
ripe-1nn.txt August, 1994
- 41 -
Example 5a:
aut-num: AS4
as-in: from AS123 100 accept NOT AS6
as-out: to AS123 announce AS4
as-in: from AS6 50 accept AS6
as-out: to AS6 announce AS4
aut-num: AS123
as-in: from AS4 100 accept AS4
as-out: to AS4 announce ANY
as-in: from AS6 100 accept AS6
as-out: to AS6 announce ANY
<further neighbours>
aut-num: AS6
as-in: from AS123 100 accept NOT AS4
as-out: to AS123 announce AS6
as-in: from AS4 50 accept AS4
as-out: to AS4 announce AS6
Note that here the configuration is slightly inconsistent. AS123
will announce AS6 to AS4 and AS4 to AS6. These announcements will be
filtered out on the receiving end. This will implement the desired
policy. Consistency checking tools might flag these cases however.
ripe-1nn.txt August, 1994
- 42 -
Example 5b:
aut-num: AS4
as-in: from AS123 100 accept ANY
as-out: to AS123 announce AS4
as-in: from AS6 50 accept AS6
as-out: AS6 AS4
aut-num: AS123
as-in: AS4 100 AS4
as-out: AS4 ANY
as-in: AS6 100 AS6
as-out: AS6 ANY
<further neighbours>
aut-num: AS6
as-in: from AS123 100 accept ANY
as-out: to AS123 announce AS6
as-in: from AS4 50 accept AS4
as-out: to AS4 announce AS6
The thing to note here is that in the ideal operational case, `all
links working' AS4 will receive announcements for AS6 from both
AS123 and AS6 itself. In this case the announcement from AS6 will
be preferred because of its lower cost and thus the private link
will be used as desired. AS6 is configured as a mirror image.
ripe-1nn.txt August, 1994
- 43 -
Example 5c:
The new feature here is that should the connection between AS4 and
AS123 fail, traffic from AS4 to destinations behind AS123 can pass
through the private link and AS6's connection to AS123.
aut-num: AS4
as-in: from AS123 100 accept ANY
as-out: to AS123 announce AS4
as-in: from AS6 50 accept AS6
as-in: from AS6 110 accept ANY
as-out: to AS6 AS4
aut-num: AS123
as-in: from AS4 1 accept AS4
as-out: to AS4 announce ANY
as-in: from AS6 1 accept AS6
as-in: from AS6 2 accept AS4
as-out: to AS6 announce ANY
<further neighbours>
aut-num: AS6
as-in: from AS123 100 accept ANY
as-out: to AS123 AS6 announce AS4
as-in: from AS4 50 accept AS4
as-out: to AS4 announce ANY
Note that it is important to make sure to propagate routing informa-
tion for both directions in backup situations like this. Connec-
tivity in just one direction is not useful at all for almost all
applications.
Note also that in case the AS6-AS123 connection breaks, AS6 will
only be able to talk to AS4. The symmetrical case (5d) is left as an
exercise to the reader.
10. Future Extensions
We envision that over time the requirements for describing routing
policy will evolve. The routing protocols will evolve to support the
requirements and the routing policy description syntax will need to
evolve as well. For that purpose, a separate document will describe
experimental syntax definitions for policy description. This docu-
ment will be updated when new objects or attributes are proposed or
modified.
Two new attributes of the AS object which are proposed and supported
by the Merit Routing Registry are as-transit and db-selector.
as-transit describes the transit preferences of an AS. It allows an
AS to describe its path preference in order to reach certain
ripe-1nn.txt August, 1994
- 44 -
destinations. The AS(s) specified in the path preference may or may
not be an immediate neighbor of the AS defined in the AS object.
as-transit accommodates policy decisions involving AS path whereas
as-in and as-out do not. It is not unusual for ASs to have routing
policies which involve path selection based on AS. Emerging proto-
cols like SDRP [13] will allow an AS to choose a path independent of
a neighboring ASs path choice. as-transit permits descriptions based
on AS path selection.
The DataBase Selector (db-selector) function allows one to take
advantage of information registered in other Registries. It permits
the selection of networks in a database based on their attributes.
It is proposed to be used within the as-in/as-out attribute family
to make the description of policy concise. For example, if an AS
has the policy of not accepting any routes from country XYZ, the AS
can use the db-selector to check a database which has a network and
country attribute and relate that information to the information in
the routing registry. The advantage of referencing another database
is that the routing registry will avoid duplicating the information
maintained in other information registries.
Detailed examples and syntax are described in document ???? [14].
ripe-1nn.txt August, 1994
- 45 -
11. References
[1] Bates, T., Jouanigot, J-M., Karrenberg, D., Lothberg, P.,
Terpstra, M., "Representation of IP Routing Policies in the
RIPE Database", RIPE-81, February 1993.
[2] Merit Network Inc.,"Representation of Complex Routing Policies
of an Autonomous System", DRAFT, March, 1994.
[3] PRIDE Tools Release 1.
See ftp.ripe.net:pride/tools/pride-tools-1.tar.Z.
[4] Merit Inc. RRDB Tools.
See rrdb.merit.edu:pub/meritrr/*
[5] The Network List Compiler.
See dxcoms.cern.ch:pub/ripe-routing-wg/nlc-2.2d.tar
[6] Lord, A., Terpstra, M., "RIPE Database Template for Networks
and Persons", DRAFT, May 1994.
[7] Karrenberg, D., "RIPE Database Template for Domains", RIPE-49,
April 1992.
[8] Lougheed, K., Rekhter, Y., "A Border Gateway Protocol 3 (BGP-
3)", RFC1267, October 1991.
[9] Rekhter, Y., Li, T., "A Border Gateway Protocol 4 (BGP-4)",
RFC-1654, May 1994.
[10] Bates, T., Karrenberg, D., Terpstra, M., "Support for Classless
Internet Addresses in the RIPE Database", DRAFT, May 1994.
[11] Karrenberg, D., "Authorisation and Notification of Changes in
the RIPE Database", RIPE-96, October 1993.
[12] Bates, T., "Support of Guarded fields within the RIPE Data-
base", ripe-108, February 1994.
[13] Estrin, D., Li, T., Rekhter, Y., Varadhan, K., Zappala, D.,
"Source Demand Routing: Packet Format and Forwarding Specifica-
tion (Version 1)", INTERNET-DRAFT, draft-ietf-sdr-sdrp-04.txt,
March 1994.
[14] ?????, "Experimental Objects and attributes for the Routing
Registry, ???, ????.
[15] Bates, T., "Specifying an `Internet Router' in the Routing
Registry", DRAFT, July 1994.
ripe-1nn.txt August, 1994
- 46 -
12. Author's Addresses
Tony Bates
RARE/PRIDE Project
c/o RIPE Network Coordination Centre
Kruislaan 409
NL-1098 SJ Amsterdam
The Netherlands
+31 20 592 5064
T.Bates(a)ripe.net
Elise Gerich
The University of Michigan
Merit Computer Network
1075 Beal Avenue
Ann Arbor, MI 48109
USA
+1 313 936 2120
epg(a)merit.edu
Laurent Joncheray
The University of Michigan
Merit Computer Network
1075 Beal Avenue
Ann Arbor, MI 48109
USA
+1 313 936 2065
lpj(a)merit.edu
Jean-Michel Jouanigot
CERN, European Laboratory for Particle Physics
CH-1211 Geneva 23
Switzerland
+41 22 767 4417
Jean-Michel.Jouanigot(a)cern.ch
Daniel Karrenberg
RIPE Network Coordination Centre
Kruislaan 409
NL-1098 SJ Amsterdam
The Netherlands
+31 20 592 5065
D.Karrenberg(a)ripe.net
ripe-1nn.txt August, 1994
- 47 -
Marten Terpstra
PRIDE Project
c/o RIPE Network Coordination Centre
Kruislaan 409
NL-1098 SJ Amsterdam
The Netherlands
+31 20 592 5064
M.Terpstra(a)ripe.net
Jessica Yu
The University of Michigan
Merit Computer Network
1075 Beal Avenue
Ann Arbor, MI 48109
USA
+1 313 936 2655
jyy(a)merit.edu
ripe-1nn.txt August, 1994
- 48 -
Appendix A - Syntax for the aut-num object.
Here is a summary of the tags associated with aut-num object itself
and their status. The first column specifies the attribute, the
second column whether this attribute is mandatory in the aut-num
object, and the third column whether this specific attribute can
occur only once per object [single], or more than once [multiple].
When specifying multiple lines per attribute, the attribute name
must be repeated. See [6] the example for the descr: attribute.
aut-num: [mandatory] [single]
descr: [mandatory] [multiple]
as-in: [optional] [multiple]
as-out: [optional] [multiple]
interas-in: [optional] [multiple]
interas-out: [optional] [multiple]
as-exclude: [optional] [multiple]
default: [optional] [multiple]
tech-c: [mandatory] [multiple]
admin-c: [mandatory] [multiple]
guardian: [mandatory] [single]
remarks: [optional] [multiple]
notify: [optional] [multiple]
maintainer: [optional] [single]
changed: [mandatory] [multiple]
source: [mandatory] [single]
Each attribute has the following syntax:
aut-num:
The autonomous system number. This must be a uniquely allo-
cated autonomous system number from an AS registry (i.e. the
RIPE NCC, the Inter-NIC, etc).
Format:
AS<positive integer between 1 and 65535>
Example:
aut-num: AS1104
Status: mandatory, only one line allowed
descr:
A short description of the Autonomous System.
Format:
free text
Status: mandatory, multiple lines allowed
as-in:
ripe-1nn.txt August, 1994
- 49 -
Example:
descr: NIKHEF section H
descr: Science Park Watergraafsmeer
descr: Amsterdam
A description of accepted routing information between AS peers.
Format:
from <aut-num> <cost> accept <routing policy expression>
The keywords from and accept are optional and can be omit-
ted.
<aut-num> refers to your AS neighbour.
<cost> is a positive integer used to express a relative
cost of routes learned. The lower the cost the more pre-
ferred the route.
<routing policy expression> can take the following for-
mats.
1. A list of one or more ASes, AS Macros, Communities or
Network Lists.
A Network List is a list of network numbers in prefix
length format, separated by commas, and surrounded by
curly brackets.
Examples:
as-in: from AS1103 100 accept AS1103
as-in: from AS786 105 accept AS1103
as-in: from AS786 10 accept AS786 HEPNET
as-in: from AS1755 110 accept AS1103 AS786
as-in: from AS3333 100 accept {192.87.45.0/16, 128.141.0.0/16}
2. A set of KEYWORDS. The following KEYWORD is
currently defined:
ANY this means anything the neighbour AS knows.
3. A logical expression of either 1 or 2 above The
current logical operators are defined as:
AND
OR
NOT
ripe-1nn.txt August, 1994
- 50 -
NOTE: if no logical operator is given between ASes,
AS-macros, Communities, Network Lists and KEYWORDS it
is implicitly evaluated as an `OR' operation. The OR
can be left out for conciseness.
Rules are grouped together using parenthesis i.e "("
and ")".
Example:
as-in: from AS1755 100 accept ANY AND NOT (AS1234 OR AS513)
as-in: from AS1755 150 accept AS1234 OR {35.0.0.0/8}
A rule can be wrapped over lines providing the
associated <aut-num>, <cost> values and from and
accept keywords are repeated and occur on con-
secutive lines.
Example:
as-in: from AS1755 100 accept ANY AND NOT (AS1234 AS513)
and
as-in: from AS1755 100 accept ANY AND NOT (
as-in: from AS1755 100 accept AS1234 AS513)
are evaluated to the same result. Please note
that the ordering of these continuing lines
matters.
Status: optional, multiple lines allowed
as-out:
A description of generated routing information sent to other AS
peers.
Format:
to <aut-num> announce <routing policy expression
The to and announce keywords are optional and can be omit-
ted.
<aut-num> refers to your AS neighbour.
<routing policy expression> is explained in the as-in
attribute definition above.
Example:
as-out: to AS1104 announce AS978
as-out: to AS1755 announce ANY
as-out: to AS786 announce ANY AND NOT (AS978)
Status: optional, multiple lines allowed
ripe-1nn.txt August, 1994
- 51 -
interas-in:
Describes incoming local preferences on an inter AS connection.
Format:
from <aut-num> [<local-rid>] [<neighbor-rid>] <preference>
accept <routing policy expression>
The keywords from and accept are optional and can be omit-
ted.
<aut-num> is an autonomous system as defined in as-in.
<local-rid> contains the IP address of the border router
in the AS describing the policy. IP address must be in
prefix length format. This field is optional.
<neighbor-rid> contains the IP address of neighbor AS's
border router from which this AS accept routes defined in
the <routing policy expression>. IP addresses must be in
prefix length format. This field is optional.
<local-info> contains the IP address of the local border
router, followed by a space, followed by the IP address of
the remote border router. IP addresses must be in prefix
length format.
<preference> is defined as follows:
(<pref-type>=<value>)
It should be noted the parenthesis ``('' and ``)'' and the
``<pref-type>'' keyword must be present for this prefer-
ence to be valid.
<pref-type> currently only supports "pref". It could be
expanded to other type of preference such as TOS/QOS as
routing technology matures.
<value> can take one of the following values:
<cost>
<cost> is a positive integer used to express a rela-
tive cost of routes learned. The lower the cost the
more preferred the route. This <cost> value is only
relevant to other interas-in attributes, not to as-in
attributes.
MED
This indicates the AS will use the
MUTLI_EXIT_DISCRIMINATOR (MED) metric, as implemented
in BGP4 and IDRP, sent from its neighbor AS.
NOTE: Combinations of MED and <cost> should be
avoided for the same destinations.
ripe-1nn.txt August, 1994
- 52 -
CAVEAT: The pref-type values may well be enhanced in
the future as more inter-ASs routing protocols intro-
duce other metrics.
<routing policy expression> is an expression as defined in
as-in above.
Examples:
interas-in: from AS1104 192.87.45.254/32 192.87.45.80/32 (pref=10) accept AS786 AS987
interas-in: from AS1104 192.87.45.254/32 192.87.45.79/32 (pref=20) accept AS987
interas-in: from AS1103 192.87.45.254/32 192.87.45.32/32 (pref=MED) accept ANY
Status: optional, multiple lines allowed
interas-out:
Format:
to <aut-num> [<local-rid>] [<neighbor-rid>] announce
[<metric>] <routing policy expression>
The keywords to and announce are optional and can be omit-
ted.
The definitions of <aut-num>, <local-rid> <neighbor-rid>,
and <routing policy expression> are identical to those
defined in interas-in.
<metric> is defined as follows:
(<metric-type>=<value>)
It should be noted the parenthesis ``('' and ``)'' and the
keywords of ``<metric-type>'' must be present for this
metric to be valid.
<metric-type> currently only supports "metric-out". It
could be expanded to other type of preference such as
TOS/QOS as routing technology matures.
<value> can take one of the following values:
<num-metric>
<num-metric> is a pre-configured metric for outbound
routes. The lower the cost the more preferred the
route. This <num-metric> value is only relevant to
other interas-out attributes, not to as-out attri-
butes.
IGP
This indicates that this means that the metric
reflects the ASs internal topology cost. The topology
is reflected here by using MED which is derived from
the AS's IGP metric.
ripe-1nn.txt August, 1994
- 53 -
NOTE: Combinations of IGP and <num-metric> should be
avoided for the same destinations.
CAVEAT: The metric-out values may well be enhanced in
the future as more interas protocols make use of
metrics.
Examples:
interas-out: to AS1104 192.87.45.254/32 192.87.45.80/32 (metric-out=10) announce AS23 AS10
interas-out: to AS1104 192.87.45.80/32 (metric-out=15) announce AS10
interas-out: to AS1103 192.87.45.254/32 (metric-out=IGP) announce ANY
Status: optional, multiple lines allowed
as-exclude:
A list of transit ASes to ignore all routes from.
Format:
exclude <aut-num> to <exclude-route-keyword>
Keywords exclude and to are optional and can again be
omitted.
<aut-num> refers to the transit AS in question.
an <exclude-route-keyword> can be ONE of the following.
1. <aut-num>
2. AS macro
3. Community
4. ANY
Examples:
as-exclude: exclude AS690 to HEPNET
This means exclude any HEPNET routes which have a route
via AS690.
as-exclude: exclude AS1800 to AS-EUNET
This means exclude any AS-EUNET routes which have a route
via AS1800.
as-exclude: exclude AS1755 to AS1104
This means exclude any AS1104 route which have a route via
AS1755.
ripe-1nn.txt August, 1994
- 54 -
as-exclude: exclude AS1104 to ANY
This means exclude all routes which have a route via
AS1104.
Status: optional, multiple lines allowed
default:
An indication of how default routing is done.
Format:
<aut-num> <relative cost> <default-expression>
where <aut-num> is the AS peer you will default route to,
and <relative cost> is the relative cost is a positive
integer used to express a preference for default. There is
no relationship to the cost used in the as-in tag. The AS
peer with the lowest cost is used for default over ones
with higher costs.
<default-expression> is optional and provides information
on how a default route is selected. It can take the fol-
lowing formats:
1. static. This indicates that a default is statically
configured to this AS peer.
2. A network list with the syntax as described in the
as-in attribute. This indicates that this list of
routes is used to generate a default route. A special
but valid value in this is the special route used by
some routing protocols to indicate default: 0.0.0.0/0
3. default. This is the same as {0.0.0.0/0}. This means
that the routing protocol between these two peers
generates a true default.
Examples:
default: AS1755 10
default: AS786 5 {140.222.0.0/16, 192.87.45.0/24}
default: AS2043 15 default
Status: optional, multiple lines allowed
tech-c:
Full name or uniquely assigned NIC-handle of a technical con-
tact person. This is someone to be contacted for technical
problems such as misconfiguration.
Format:
<firstname> <initials> <lastname> or <nic-handle>
ripe-1nn.txt August, 1994
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Example:
tech-c: John E Doe
tech-c: JED31
Status: mandatory, multiple lines allowed
admin-c:
Full name or uniquely assigned NIC-handle of an administrative
contact person. In many cases this would be the name of the
guardian.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Example:
admin-c: Joe T Bloggs
admin-c: JTB1
Status: mandatory, multiple lines allowed
guardian:
Mailbox of the guardian of the Autonomous system.
Format:
<email-address>
The <email-address> should be in RFC822 domain format
wherever possible.
Example:
guardian: as1104-guardian(a)nikhef.nl
Status: mandatory, only one line and e-mail address allowed
remarks:
Remarks/comments, to be used only for clarification.
Format:
free text
Example:
remarks: Multihomed AS talking to AS1755 and AS786
remarks: Will soon connect to AS1104 also.
Status: optional, multiple lines allowed
notify:
The notify attribute contains an email address to which notifi-
cations of changes to this object should be sent. See also
[11].
ripe-1nn.txt August, 1994
- 56 -
Format:
<email-address>
The <email-address> should be in RFC822 domain syntax
wherever possible.
Example:
notify: Marten.Terpstra(a)ripe.net
Status: optional, multiple lines allowed
maintainer:
The maintainer attribute contains a registered maintainer name.
See also [11].
Format:
<registered maintainer name>
Example:
maintainer: RIPE-DBM
Status: optional, multiple lines allowed
changed:
Who changed this object last, and when was this change made.
Format:
<email-address> YYMMDD
<email-address> should be the address of the person who
made the last change. YYMMDD denotes the date this change
was made.
Example:
changed: johndoe(a)terabit-labs.nn 900401
Status: mandatory, multiple lines allowed
source:
Source of the information.
This is used to separate information from different sources
kept by the same database software. For RIPE database entries
the value is fixed to RIPE.
Format:
RIPE
Status: mandatory, only one line allowed
ripe-1nn.txt August, 1994
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Appendix B - Syntax details for the community object.
Here is a summary of the tags associated with community object
itself and their status. The first column specifies the attribute,
the second column whether this attribute is mandatory in the commun-
ity object, and the third column whether this specific attribute can
occur only once per object [single], or more than once [multiple].
When specifying multiple lines per attribute, the attribute name
must be repeated. See [6] the example for the descr: attribute.
community: [mandatory] [single]
descr: [mandatory] [multiple]
authority: [mandatory] [single]
guardian: [mandatory] [single]
tech-c: [mandatory] [multiple]
admin-c: [mandatory] [multiple]
remarks: [optional] [multiple]
notify: [optional] [multiple]
maintainer: [optional] [single]
changed: [mandatory] [multiple]
source: [mandatory] [single]
Each attribute has the following syntax:
community:
Name of the community. The name of the community should be
descriptive of the community it describes.
Format:
Upper case text string which cannot start with "AS" or any
of the <routing policy expression> KEYWORDS. See Appendix
A.
Example:
community: WCW
Status: mandatory, only one line allowed
descr:
A short description of the community represented.
Format:
free text
Example:
descr: Science Park Watergraafsmeer
descr: Amsterdam
Status: mandatory, multiple lines allowed
ripe-1nn.txt August, 1994
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authority:
The formal authority for this community. This could be an
organisation, institute, committee, etc.
Format:
free text
Example:
authority: WCW LAN Committee
Status: mandatory, only one line allowed
guardian:
Mailbox of the guardian of the community.
Format:
<email-address>
The <email-address> should be in RFC822 domain format
wherever possible.
Example:
guardian: wcw-guardian(a)nikhef.nl
Status: mandatory, only one line and email address allowed
tech-c:
Full name or uniquely assigned NIC-handle of an technical con-
tact person for this community.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Example:
tech-c: John E Doe
tech-c: JED31
Status: mandatory, multiple lines allowed
admin-c:
Full name or uniquely assigned NIC-handle of an administrative
contact person. In many cases this would be the name of the
guardian.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Example:
admin-c: Joe T Bloggs
admin-c: JTB1
ripe-1nn.txt August, 1994
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Status: mandatory, multiple lines allowed
remarks:
Remarks/comments, to be used only for clarification.
Format:
free text
Example:
remarks: Temporary community
remarks: Will be removed after split into ASes
Status: optional, multiple lines allowed
notify:
The notify attribute contains an email address to which notifi-
cations of changes to this object should be send. See also
[11].
Format:
<email-address>
The <email-address> should be in RFC822 domain syntax
wherever possible.
Example:
notify: Marten.Terpstra(a)ripe.net
Status: optional, multiple lines allowed
maintainer:
The maintainer attribute contains a registered maintainer name.
See also [11].
Format:
<registered maintainer name>
Example:
maintainer: RIPE-DBM
Status: optional, multiple lines allowed
changed:
Who changed this object last, and when was this change made.
Format:
<email-address> YYMMDD
<email-address> should be the address of the person who
made the last change. YYMMDD denotes the date this change
was made.
ripe-1nn.txt August, 1994
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Example:
changed: johndoe(a)terabit-labs.nn 900401
Status: mandatory, multiple lines allowed
source:
Source of the information.
This is used to separate information from different sources
kept by the same database software. For RIPE database entries
the value is fixed to RIPE.
Format:
RIPE
Status: mandatory, only one line allowed
ripe-1nn.txt August, 1994
- 61 -
Appendix C - AS Macros syntax definition.
Here is a summary of the tags associated with as-macro object itself
and their status. The first column specifies the attribute, the
second column whether this attribute is mandatory in the as-macro
object, and the third column whether this specific attribute can
occur only once per object [single], or more than once [multiple].
When specifying multiple lines per attribute, the attribute name
must be repeated. See [6] the example for the descr: attribute.
as-macro: [mandatory] [single]
descr: [mandatory] [multiple]
as-list: [mandatory] [multiple]
guardian: [mandatory] [single]
tech-c: [mandatory] [multiple]
admin-c: [mandatory] [multiple]
remarks: [optional] [multiple]
notify: [optional] [multiple]
maintainer: [optional] [single]
changed: [mandatory] [multiple]
source: [mandatory] [single]
Each attribute has the following syntax:
as-macro:
The name of a macro containing at least two Autonomous Systems
grouped together for ease of administration.
Format:
AS-<string>
The <string> should be in upper case and not contain any
special characters.
Example:
as-macro: AS-EBONE
Status: mandatory, only one line allowed
descr:
A short description of the Autonomous System Macro.
Format:
free text
Example:
descr: Macro for EBONE connected ASes
Status: mandatory, multiple lines allowed
ripe-1nn.txt August, 1994
- 62 -
as-list:
The list of ASes that make up this macro.
Format:
<aut-num> <aut-num> ...
See Appendix A for <aut-num> definition.
Example:
as-list: AS786 AS513 AS1104
Status: mandatory, multiple lines allowed
guardian:
Mailbox of the guardian of this AS macro.
Format:
<email-address>
The <email-address> should be in RFC822 domain format
wherever possible.
Example:
guardian: as-ebone-guardian(a)ebone.net
Status: mandatory, only one line and e-mail address allowed
tech-c:
Full name or uniquely assigned NIC-handle of a technical con-
tact person for this macro. This is someone to be contacted for
technical problems such as misconfiguration.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Examples:
tech-c: John E Doe
tech-c: JED31
Status: mandatory, multiple lines allowed
admin-c:
Full name or uniquely assigned NIC-handle of an administrative
contact person. In many cases this would be the name of the
guardian.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Examples:
ripe-1nn.txt August, 1994
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admin-c: Joe T Bloggs
admin-c: JTB1
Status: mandatory, multiple lines allowed
remarks:
Remarks/comments, to be used only for clarification.
Format:
free text
Example:
remarks: AS321 will be removed from this Macro shortly
Status: optional, multiple lines allowed
notify:
The notify attribute contains an email address to which notifi-
cations of changes to this object should be send. See also
[11].
Format:
<email-address>
The <email-address> should be in RFC822 domain syntax
wherever possible.
Example:
notify: Marten.Terpstra(a)ripe.net
Status: optional, multiple lines allowed
maintainer:
The maintainer attribute contains a registered maintainer name.
See also [11].
Format:
<registered maintainer name>
Example:
maintainer: RIPE-DBM
Status: optional, multiple lines allowed
changed:
Who changed this object last, and when was this change made.
Format:
<email-address> YYMMDD
ripe-1nn.txt August, 1994
- 64 -
<email-address> should be the address of the person who
made the last change. YYMMDD denotes the date this change
was made.
Example:
changed: johndoe(a)terabit-labs.nn 900401
Status: mandatory, multiple lines allowed
source:
Source of the information.
This is used to separate information from different sources
kept by the same database software. For RIPE database entries
the value is fixed to RIPE.
Format:
RIPE
Status: mandatory, only one line allowed
ripe-1nn.txt August, 1994
- 65 -
Appendix D - Syntax for the "route" object.
There is a summary of the tags associated with community object
itself and their status. The first column specifies the attribute,
the second column whether this attribute is mandatory in the commun-
ity object, and the third column whether this specific attribute can
occur only once per object [single], or more than once [multiple].
When specifying multiple lines per attribute, the attribute name
must be repeated. See [6] the example for the descr: attribute.
route: [mandatory] [single]
descr: [mandatory] [multiple]
origin: [mandatory] [single]
hole: [optional] [multiple]
withdrawn: [optional] [multiple]
comm-list: [optional] [multiple]
remarks: [optional] [multiple]
notify: [optional] [multiple]
maintainer: [optional] [single]
changed: [mandatory] [multiple]
source: [mandatory] [single]
Each attribute has the following syntax:
route:
Route being announced.
Format:
Classless representation of a route with the RIPE database
known as the "prefix length" representation. See [10] for
more details on classless representations.
Examples:
route: 192.87.45.0/24
This represents addressable bits 192.87.45.0 to
192.87.45.255.
route: 192.1.128.0/17
This represents addressable bits 192.1.128.0 to
192.1.255.255.
Status: mandatory, only one line allowed
origin:
The autonomous system announcing this route.
Format:
<aut-num>
ripe-1nn.txt August, 1994
- 66 -
See appendix A for <aut-num> syntax.
Example:
origin: AS1104
Status: mandatory, only one line allowed
hole:
Denote the parts of the address space covered this route object
to which the originator does not provide connectivity.
Format:
Classless representation of a route with the RIPE database
known as the "prefix length" representation. See [10] for
more details on classless representations. It should be
noted that is sub-aggregate must be a component of that
registered in the route object.
Example:
hole: 193.0.4.0/24
Status: optional, multiple lines allowed
withdrawn:
Used to denote the day this route has been withdrawn from the
Internet routing mesh. This will be usually be used when a less
specific aggregate route is now routed the more specific (i.e.
this route) is not need anymore. It should be noted that this
date cannot be in the future.
Format:
YYMMDD
YYMMDD denotes the date this route was withdrawn.
Example:
withdrawn: 940711
Status: optional, multiple lines allowed
comm-list:
List of one or more communities this route is part of.
Format:
<community> <community> ...
See Appendix B for <community> definition.
Example:
comm-list: HEP LEP
ripe-1nn.txt August, 1994
- 67 -
Status: optional, multiple lines allowed
remarks:
Remarks/comments, to be used only for clarification.
Format:
free text
Example:
remarks: Multihomed AS talking to AS1755 and AS786
remarks: Will soon connect to AS1104 also.
Status: optional, multiple lines allowed
notify:
The notify attribute contains an email address to which notifi-
cations of changes to this object should be send. See also
[11].
Format:
<email-address>
The <email-address> should be in RFC822 domain syntax
wherever possible.
Example:
notify: Marten.Terpstra(a)ripe.net
Status: optional, multiple lines allowed
maintainer:
The maintainer attribute contains a registered maintainer name.
See also [11].
Format:
<registered maintainer name>
Example:
maintainer: RIPE-DBM
Status: optional, multiple lines allowed
changed:
Who changed this object last, and when was this change made.
Format:
<email-address> YYMMDD
<email-address> should be the address of the person who
made the last change. YYMMDD denotes the date this change
was made.
ripe-1nn.txt August, 1994
- 68 -
Example:
changed: johndoe(a)terabit-labs.nn 900401
Status: mandatory, multiple lines allowed
source:
Source of the information.
This is used to separate information from different sources
kept by the same database software. For RIPE database entries
the value is fixed to RIPE.
Format:
RIPE
Status: mandatory, only one line allowed
ripe-1nn.txt August, 1994
- 69 -
Appendix E - List of reserved words
The following list of words are reserved for use within the attri-
butes of the AS object. The use of these words is solely for the
purpose of clarity. All keywords must be lower case.
accept
announce
exclude
from
to
transit
Examples of the usage of the reserved words are:
as-in: from neighborAS accept route
as-out: to neighborAS announce route
as-exclude: exclude ASpath to destination
as-transit: transit ASpath to destination
default: from neighborAS accept route
default: to neighborAS announce route
Note: that as-transit is an experimental attribute. See section 10.
ripe-1nn.txt August, 1994
- 70 -
Appendix F - Motivations for RIPE-81++
This appendix gives motivations for the major changes in this propo-
sal from ripe-81. (It is not complete yet).
The main goals of the routing registry rework are:
SPLIT
Separate the allocation and routing registry functions into
different database objects. This will facilitate data manage-
ment if the Internet registry and routing registry functions
are separated (like in other parts of the world). It will also
make more clear what is part of the routing registry and who
has authority to change allocation vs. routing data.
CIDR
Add the possibility to specify classless routes in the routing
registry. Classless routes are being used in Internet produc-
tion now. Aggregation information in the routing registry is
necessary for network layer troubleshooting. It is also neces-
sary because aggregation influences routing policies directly.
CALLOC
Add the possibility to allocate address space on classless
boundaries in the allocation registry. This is a way to
preserve address space.
CLEAN
To clean up some of the obsolete and unused parts of the rout-
ing registry.
The major changes are now discussed in turn:
Introduce Classless Addresses
CIDR, CALLOC
Introduce route object.
SPLIT, CIDR and CALLOC.
Delete obsolete attributes from inetnum.
CLEAN.
ripe-1nn.txt August, 1994
- 71 -
Delete RIPE-DB and LOCAL from routing policy expressions.
CLEAN
Allow multiple ASes to originate the same route
Because it is being done. CIDR. Made possible by SPLIT.
ripe-1nn.txt August, 1994
- 72 -
Appendix G - Transition strategy from RIPE-81 to RIPE-81++
Transition from the routing registry described by ripe-81 to the
routing registry described in this document is a straightforward
process once the new registry functions have been implemented in the
database software and are understood by the most commonly used
registry tools. The routing related attributes in the classful inet-
num objects of ripe-81 can be directly translated into new routing
objects. Then these attributes can be deleted from the inetnum
object making that object if conform to the new schema.
Proposed transition steps:
1) Implement classless addresses and new object definition in the
database software.
2) Make common tools understand the new schema and prefer it if
both old and new are present.
3) Invite everyone to convert their data to the new format. This
can be encouraged by doing conversions automatically and pro-
posing them to maintainers.
4) At a flag day remove all remaining routing information from the
inetnum objects. Before the flag day all usage of obsoleted
inetnum attributes has to cease and all other routing registry
functions have to be taken over by the new objects and attri-
butes.
The current estimate is that point three can be reached in the Sum-
mer 1994 if the draft is accepted by mid-June. The flag day should
be scheduled 3-4 months after this point.
ripe-1nn.txt August, 1994
1
0
Find below the last iteration of ripe-81++. This has changes to the
text and syntax for interas-in / interas-out following some comments
to me from Merit. The ordering issues still exists but as stated
before this will be decided by the working group chair. Please also
note my earlier plea that we must agreement on this at the RIPE
meeting if this is to be implemented in a timely manner and preferably
before. Working group chairs please take note and see if you can't get
this agreed within your groups before hand. Please note that the TOC
will not be completed until the issued docment.
versions online as usual from:
ftp://ftp.ripe.net/ripe/drafts/ripe-81++.ps
ftp://ftp.ripe.net/ripe/drafts/ripe-81++.txt
--Tony.
Representation of IP Routing Policies
in a Routing Registry
(ripe-81++)
DRAFT DRAFT DRAFT
Tony Bates
Elise Gerich
Laurent Joncheray
Jean-Michel Jouanigot
Daniel Karrenberg
Marten Terpstra
Jessica Yu
Document-ID: ripe-1nn
Obsoletes: ripe-81
July, 1994
ABSTRACT
This document is an update to the original `ripe-
81'[1] proposal for representing and storing routing
polices within the RIPE database. It incorporates
several extensions proposed by Merit Inc.[2] and gives
details of a generalised IP routing policy representa-
tion to be used by all Internet routing registries. It
acts as both tutorial and provides details of database
objects and attributes that use and make up a routing
registry.
ripe-1nn.txt July, 1994
- 2 -
Table of Contents
1 Introduction ................................................ ?
2 Organisation of this Document ............................... ?
3 General Representation of Policy Information ................ ?
4 The Routing Registry and the RIPE Database .................. ?
5 The Route Object ............................................ ?
6 The Autonomous System Object ................................ ?
7 The AS Macro Object ......................................... ?
8 The Community Object ........................................ ?
9 Representation of Routing Policies .......................... ?
10 Future Extensions .......................................... ?
11 References ................................................. ?
12 Authors Addresses .......................................... ?
Appendix A - Syntax for the "aut-num" object .................. ?
Appendix B - Syntax for the "community" object ................ ?
Appendix C - Syntax for the "as-macro" object ................. ?
Appendix D - Syntax for the "route" object .................... ?
Appendix E - List of reserved words ........................... ?
Appendix F - Motivations for RIPE-81++ ........................ ?
Appendix G - Transition strategy from RIPE-81 to RIPE-81++ .... ?
ripe-1nn.txt July, 1994
- 3 -
1. Introduction
This document is a much revised version of the RIPE routing registry
document known as ripe-81[1]. Since its inception in February, 1993
and the establishment of the RIPE routing registry, several addi-
tions and clarifications have come to light which can be better
presented in a single updated document rather than separate addenda.
Some of the text remains the same the as the original ripe-81 docu-
ment keeping its tutorial style mixed with details of the RIPE data-
base objects relating to routing policy representation. However
this document does not repeat the background and historical remarks
in ripe-81. For these please refer to the original document. It
should be noted that whilst this document specifically references
the RIPE database and the RIPE routing registry one can easily read
"Regional routing registry" in place of RIPE as this representation
is certainly general and flexible enough to be used outside of the
RIPE community incorporating many ideas and features from other
routing registries in this update.
As you can see this document has a new RIPE document identification
number but can also be referred to as ripe-81++. Appendix F summar-
ises the changes from ripe-81 plus the motivation for these changes.
We would like to acknowledge many people for help with this docu-
ment. Specifically, Peter Lothberg who was a co-author of the ori-
ginal ripe-81 document for his many ideas and Gilles Farrache. We
would also like to thank the RIPE routing working group for their
review and comment. Finally, we like to thank Merit Inc. for many
constructive comments and ideas and making the routing registry a
worldwide Internet service. We would also like to acknowledge the
funding provided by the PRIDE project run in conjunction with the
RARE Technical Program, RIPE and the RIPE NCC without which this
paper would not have been possible.
2. Organisation of this Paper
This paper acts as both a basic tutorial for understanding routing
policy and provides details of objects and attributes used within an
Internet routing registry to store routing policies. Section 3
describes general issues about IP routing policies and their
representation in routing registries. Experienced readers may wish
to skip this section. Section 4 provides an overview of the RIPE
database, its basic concepts, schema and objects which make up the
database itself. It highlights the way in which the RIPE database
splits routing information from allocation information. Sections 5,
6, 7 and 8 detail all the objects associated with routing policy
representation. Section 9 gives a fairly extensive "walk through"
of how these objects are used for expressing routing policy and the
general principles behind their use. Section 10 provides a list of
references used throughout this document. Appendix A, B, C and D
document the formal syntax for the database objects and attributes.
Appendix F details the main changes from ripe-81 and motivations for
these changes. Appendix G tackles the issues of transition from
ripe-1nn.txt July, 1994
- 4 -
ripe-81 to ripe-81++.
ripe-1nn.txt July, 1994
- 5 -
3. General Representation of Policy Information
Networks, Network Operators and Autonomous Systems
Throughout this document an effort is made to be consistent with
terms so as not to confuse the reader.
When we talk about "networks" we mean physical networks which have a
unique classless IP network number: Layer 3 entities. We do not mean
organisations.
We call the organisations operating networks "network operators".
For the sake of the examples we divide network operators into two
categories: "service providers" and "customers". A "service pro-
vider" is a network operator who operates a network to provide
Internet services to different organisations, its "customers". The
distinction between service providers and customers is not clear
cut. A national research networking organisation frequently acts as
a service provider to Universities and other academic organisations,
but in most cases it buys international connectivity from another
service provider. A University networking department is a customer
of the research networking organisation but in turn may regard
University departments as its customers.
An Autonomous System (AS) is a group of IP networks having a single
clearly defined routing policy which is run by one or more network
operators. Inside ASes IP packets are routed using one or more Inte-
rior Routing Protocols (IGPs). In most cases interior routing deci-
sions are based on metrics derived from technical parameters like
topology, link speeds and load(1).
ASes exchange routing information with other ASes using Exterior
Routing Protocols (EGPs). Exterior routing decisions are frequently
based on policy based rules rather than purely on technical parame-
ters. Tools are needed to configure complex policies and to commun-
icate those policies between ASes while still ensuring proper opera-
tion of the Internet as a whole. Some EGPs like BGP-3 [8] and BGP-4
[9] provide tools to filter routing information according to policy
rules and more. None of them provides a mechanism to publish or com-
municate the policies themselves. Yet this is critical for opera-
tional coordination and fault isolation among network operators and
thus for the operation of the global Internet as a whole. This
document describes a "Routing Registry" providing this functional-
ity.
_________________________
(1) The entity we refer to as an AS is frequently and
more generally called a routing domain with the AS just
being an implementation vehicle. We have decided to use
the term AS exclusively because it relates more direct-
ly with the database objects and routing tools. By us-
ing only one term we hope to reduce the number of con-
cepts and to avoid confusion. The academically inclined
reader may forgive us.
ripe-1nn.txt July, 1994
- 6 -
Routing Policies
The exchange of routing information between ASes is subject to rout-
ing policies. Consider the case of two ASes, X and Y exchanging
routing information:
NET1 ...... ASX <---> ASY ....... NET2
ASX knows how to reach a network called NET1. It does not matter
whether NET1 is belonging to ASX or some other AS which exchanges
routing information with ASX either directly or indirectly; we just
assume that ASX knows how to direct packets towards NET1. Likewise
ASY knows how to reach NET2.
In order for traffic from NET2 to NET1 to flow between ASX and ASY,
ASX has to announce NET1 to ASY using an external routing protocol.
This states that ASX is willing to accept traffic directed to NET1
from ASY. Policy thus comes into play first in the decision of ASX
to announce NET1 to ASY.
In addition ASY has to accept this routing information and use it.
It is ASY's privilege to either use or disregard the information
that ASX is willing to accept traffic for NET1. ASY might decide not
to use this information if it does not want to send traffic to NET1
at all or if it considers another route more appropriate to reach
NET1.
So in order for traffic in the direction of NET1 to flow between ASX
and ASY, ASX must announce it to ASY and ASY must accept it from
ASX:
resulting packet flow towards NET1
<<===================================
|
|
announce NET1 | accept NET1
--------------> + ------------->
|
AS X | AS Y
|
<------------- + <--------------
accept NET2 | announce NET2
|
|
resulting packet flow towards NET2
===================================>>
Ideally, and seldom practically, the announcement and acceptance
policies of ASX and ASY are identical.
ripe-1nn.txt July, 1994
- 7 -
In order for traffic towards NET2 to flow, announcement and accep-
tance of NET2 must be in place the other way round. For almost all
applications connectivity in just one direction is not useful at
all.
It is important to realise that with current destination based for-
warding technology routing policies must eventually be expressed in
these terms. It is relatively easy to formulate reasonable policies
in very general terms which CANNOT be expressed in terms of announc-
ing and accepting networks. With current technology such policies
are almost always impossible to implement.
Usually policies are not configured for each network separately but
for groups of networks. In practise these groups are almost always
defined by the networks forming one or more ASes.
Routing Policy limitations
The generic example of a reasonable but un-implementable routing is
a split of already joined packet streams based on something other
than destination address. Once traffic for the same destination
network passes the same router, or the same AS at our level of
abstraction, it will take exactly the same route to the destina-
tion(2).
In a concrete example AS Z might be connected to the outside world
by two links. AS Z wishes to reserve these links for different
kinds of traffic, let's call them black and white traffic. For this
purpose the management of AS Z keeps two lists of ASes, the black
and the white list. Together these lists comprise all ASes in the
world reachable from AS Z.
"W"
<--->
... AS Z .... NET 3
<--->
"B"
It is quite possible to implement the policy for traffic originating
in AS Z: AS Z will only accept announcements for networks in white
ASes on the white link and will only accept announcements for net-
works in black ASes on the black link. This causes traffic from
networks within AS Z towards white ASes to use the white link and
likewise traffic for black ASes to use the black link.
Note that this way of implementing things makes it necessary to
decide on the colour of each new AS which appears before traffic can
be sent to it from AS Z. A way around this would be to accept only
_________________________
(2) Disregarding special cases like "type of service"
routing, load sharing and routing instabilities.
ripe-1nn.txt July, 1994
- 8 -
white announcements via the white link and to accept all but white
announcements on the black link. That way traffic from new ASes
would automatically be sent down the black link and AS Z management
would only need to keep the list of white ASes rather than two
lists.
Now for the unimplementable part of the policy. This concerns
traffic towards AS Z. Consider the following topology:
B AS ---) "W"
W AS ---) --->
B AS ---)>> AS A ---> ... AS Z .... NET 3
B AS ---) --->
W AS ---) "B"
As seen from AS Z there are both black and white ASes "behind" AS A.
Since ASes can make routing decisions based on destination only, AS
A and all ASes between AS A and the two links connecting AS Z can
only make the same decision for traffic directed at a network in AS
Z, say NET 3. This means that traffic from both black and white
ASes towards NET 3 will follow the same route once it passes through
AS A. This will either be the black or the white route depending on
the routing policies of AS A and all ASes between it and AS Z.
The important thing to note is that unless routing and forwarding
decisions can be made based on both source and destination
addresses, policies like the "black and white" example cannot be
implemented in general because "once joined means joined forever".
Access Policies
Access policies contrary to routing policies are not necessarily
defined in terms of ASes. The very simplest type of access policy is
to block packets from a specific network S from being forwarded to
another network D. A common example is when some inappropriate use
of resources on network D has been made from network S and the prob-
lem has not been resolved yet. Other examples of access policies
might be resources only accessible to networks belonging to a par-
ticular disciplinary group or community of interest. While most of
these policies are better implemented at the host or application
level, network level access policies do exist and are a source of
connectivity problems which are sometimes hard to diagnose. There-
fore they should also be documented in the routing registry accord-
ing to similar requirements as outlined above.
Routing v Allocation information
The RIPE database contains both routing registry and address space
allocation registry information. In the past the database schema
combined this information. Because RIPE was tasked with running both
an allocation and routing registry it seemed natural to initially
ripe-1nn.txt July, 1994
- 9 -
combine these functions. However, experience has shown that a clear
separation of routing information from allocation is desirable.
Often the maintainer of the routing information is not the same as
the maintainer of the allocation information. Also, in other parts
of the world there are different registries for each kind of infor-
mation.
Whilst the actual routing policy objects will be introduced in the
next section it is worthy of note that a transition from the current
objects will be required. This is described with in Appendix G.
This split in information represents a significant change in the
representational model of the RIPE database. Appendix F expands on
the reasons for this a little more.
Tools
The network operators will need a series of tools for policy rout-
ing. Some tools are already available to perform some of the tasks.
Most notably, the PRIDE tools [3] from the PRIDE project started in
September 1993 as well as others produced by Merit Inc [4] and CERN
[5].
These tools will enable them to use the routing policy stored in the
RIPE routing registry to perform such tasks as check actual routing
against policies defined, ensure consistency of policies set by dif-
ferent operators, and simulate the effects of policy changes.
Work continues on producing more useful tools to service the Inter-
net community.
ripe-1nn.txt July, 1994
- 10 -
4. The Routing Registry and the RIPE Database
One of the activities of RIPE is to maintain a database of Euro-
pean IP networks, DNS domains and their contact persons along with
various other kinds of network management information. The database
content is public and can be queried using the whois protocol as
well as retrieved as a whole. This supports NICs/NOCs all over
Europe and beyond to perform their respective tasks.
The RIPE database combines both allocation registry and routing
registry functions. The RIPE allocation registry contains data
about address space allocated to specific enterprises and/or
delegated to local registries as well as data about the domain name
space. The allocation registry is described in separate documents
[6,7] and outside the scope of this document.
Database Objects
Each object in the database describes a single entity in the real
world. This basic principle means that information about that
entity should only be represented in the corresponding data-
base object and not be repeated in other objects. The whois ser-
vice can automatically display referenced objects where appropriate.
The types of objects stored in the RIPE database are summarised in
the table below:
R Object Describes References
____________________________________________________________________
B person contact persons
A inetnum IP address space person
A domain DNS domain person
R aut-num autonomous system person
(aut-num,community)
R as-macro a group of autonomous systems person, aut-num
R community community person
R route a route being announced aut-num, community
R clns CLNS address space and routing person
The first column indicates whether the object is part of the alloca-
tion registry (A), the routing registry (R) or both (B). The last
column indicates the types of objects referenced by the particular
type of object. It can be seen that almost all objects reference
contact persons.
Objects are described by attributes value pairs, one per line.
Objects are separated by empty lines. An attribute that consists
ripe-1nn.txt July, 1994
- 11 -
of multiple lines should have the attribute name repeated on
consecutive lines. The information stored about network 192.87.45.0
consists of three objects, one network object and two person
objects and looks like this:
inetnum: 192.87.45.0
netname: RIPE-NCC
descr: RIPE Network Coordination Centre
descr: Amsterdam, Netherlands
country: NL
admin-c: Daniel Karrenberg
tech-c: Marten Terpstra
rev-srv: ns.ripe.net
rev-srv: ns.eu.net
notify: ops(a)ripe.net
changed: tony(a)ripe.net 940110
source: RIPE
person: Daniel Karrenberg
address: RIPE Network Coordination Centre (NCC)
address: Kruislaan 409
address: NL-1098 SJ Amsterdam
address: Netherlands
phone: +31 20 592 5065
fax-no: +31 20 592 5090
e-mail: dfk(a)ripe.net
nic-hdl: DK58
changed: ripe-dbm(a)ripe.net 920826
source: RIPE
person: Marten Terpstra
address: RIPE Network Coordination Centre (NCC)
address: PRIDE Project
address: Kruislaan 409
address: NL-1098 SJ Amsterdam
address: Netherlands
phone: +31 20 592 5064
fax-no: +31 20 592 5090
e-mail: Marten.Terpstra(a)ripe.net
nic-hdl: MT2
notify: marten(a)ripe.net
changed: marten(a)ripe.net 931230
source: RIPE
Objects are stored and retrieved in this tag/value format. The RIPE
NCC does not provide differently formatted reports because any
desired format can easily be produced from this generic one.
ripe-1nn.txt July, 1994
- 12 -
Routing Registry Objects
The main objects comprising the routing registry are "aut-num" and
"route", describing an autonomous system and a route respectively.
It should be noted that routes not described in the routing registry
should never be routed in the Internet itself.
The autonomous system (aut-num) object provides contact information
for the AS and describes the routing policy of that AS. The routing
policy is described by enumerating all neighbouring ASes with which
routing information is exchanged. For each neighbour the routing
policy is described in terms of exactly what is being sent
(announced) and allowed in (accepted). It is important to note that
this is exactly the part of the global policy over which an AS has
direct control. Thus each aut-num object describes what can indeed
be implemented and enforced locally by the AS concerned. Combined
together all the aut-num objects provide the global routing graph
and permit to deduce the exact routing policy between any two ASes.
While the aut-num objects describe how routing information is pro-
pagated, the route object describes a single route injected into the
external routing mesh. The route object references the AS injecting
(originating) the route and thereby indirectly provides contact
information for the originating AS. This reference also provides the
primary way of grouping routes into larger collections. This is
necessary because describing routing policy on the level of single
routes would be awkward to impractical given the number of routes in
the Internet which is about 20,000 at the time of this writing.
Thus routing policy is most often defined for groups of routes by
originating AS. This method of grouping is well supported by
current exterior routing protocols. The route object also refer-
ences community objects described below to provide another method of
grouping routes. Modification of aut-num object itself and the
referencing by route objects is strictly protected to provide net-
work operators control over the routing policy description and the
routes originated by their ASes.
Sometimes even keeping track of groups of routes at the AS level is
cumbersome. Consider the case of policies described at the transit
provider level which apply transitively to all customers of the
transit provider. Therefore another level of grouping is provided by
the as-macro object which provides groups of ASes which can be
referenced in routing policies just like single ASes. Membership of
as-macro groups is also strictly controlled.
Sometimes there is a need to group routes on different criteria than
ASes for purposes like statistics or local access policies. This is
provided by the community object. A community object is much like
an AS but without a routing policy. It just describes a group of
routes. This is not supported at all by exterior routing protocols
and depending on aggregation of routes may not be generally usable
to define routing policies. It is suitable for local policies and
non-routing related purposes.
ripe-1nn.txt July, 1994
- 13 -
These routing related objects will be described in detail in the
sections below.
ripe-1nn.txt July, 1994
- 14 -
5. The Route Object
As stated in the previous chapter routing and address space alloca-
tion information are now clearly separated. This is performed with
the introduction of the route object. The route object will contain
all the information regarding a routing announcement.
All routing related attributes are removed from the inetnum object.
Some old attributes are obsoleted: connect, routpr-l, bdryg-l, nsf-
in, nsf-out, gateway). The currently useful routing attributes are
moved to the route object: aut-sys becomes origin, ias-int will be
encoded as part of the "to be proposed" `border-router' object and
comm-list simply moves. See [6] for detail of the "inetnum" object
definition.
The information in the old inetnum object
inetnum: 192.87.45.0
netname: RIPE-NCC
descr: RIPE Network Coordination Centre
descr: Amsterdam, Netherlands
country: NL
admin-c: Daniel Karrenberg
tech-c: Marten Terpstra
connect: RIPE NSF WCW
aut-sys: AS3333
comm-list: SURFNET
ias-int: 192.87.45.80 AS1104
ias-int: 192.87.45.6 AS2122
ias-int: 192.87.45.254 AS2600
rev-srv: ns.ripe.net
rev-srv: ns.eu.net
notify: ops(a)ripe.net
changed: tony(a)ripe.net 940110
source: RIPE
will be distributed over two objects:
ripe-1nn.txt July, 1994
- 15 -
inetnum: 192.87.45.0
netname: RIPE-NCC
descr: RIPE Network Coordination Centre
descr: Amsterdam, Netherlands
country: NL
admin-c: Daniel Karrenberg
tech-c: Marten Terpstra
rev-srv: ns.ripe.net
rev-srv: ns.eu.net
notify: ops(a)ripe.net
changed: tony(a)ripe.net 940110
source: RIPE
route: 192.87.45.0/24
descr: RIPE Network Coordination Centre
origin: AS3333
comm-list: SURFNET
changed: dfk(a)ripe.net 940427
source: RIPE
The route object is used to represent a single route originated into
the Internet routing mesh. The actual syntax is given in Appendix
D. However, there are several important aspects of the attributes
worthy of note.
The value of the route attribute will be a classless address. It
represents the exact route being injected into the routing mesh.
The representation of classless addresses is described in [10].
The value of the origin attribute will be an AS reference of the
form AS1234 referring to an aut-num object. It represents the AS
injecting this route into the routing mesh. The "aut-num" object
(see below) thus referenced provides all the contact information for
this route.
Special cases: There can only be a single originating AS in each
route object. However in todays Internet sometimes a route is
injected by more than one AS. This situation is potentially
dangerous as it can create conflicting routing policies for that
route and requires coordination between the originating ASes. In
the routing registry this is represented by multiple route objects.
This is a departure from the one route (net), one AS principle of
the ripe-81 routing registry. The consequences for the different
tools based in the routing registry will need to be evaluated and
possibly additional consistency checking of the database is needed.
ripe-1nn.txt July, 1994
- 16 -
The examples below will illustrate the usage of the route object
further. Suppose three chunks of address space of 2 different
enterprises represented by the following inetnum objects:
Examples
inetnum: 193.0.1.0
netname: ENT-1
descr: Enterprise 1
...
inetnum: 193.0.8.0
netname: ENT-2
descr: Enterprise 2
...
inetnum: 193.0.9.0
netname: ENT-2-SPEC
descr: Enterprise 2
...
Supposing that the Enterprises have their own AS numbers straight
application of routing without aggregation would yield:
route: 193.0.1.0/24
descr: Enterprise 1
origin: AS1
...
route: 193.0.8.0/24
descr: Enterprise 2
origin: AS2
...
route: 193.0.9.0/24
descr: Enterprise 2
origin: AS2
...
NB: This representation can be achieved by straight translation from
the ripe-81 representation. See Appendix G for more details.
Homogeneous Aggregation
The two chunks of address space of Enterprise 2 can be represented
by one aggregate route turning two route objects into one and poten-
tially saving routing table space for one route.
ripe-1nn.txt July, 1994
- 17 -
route: 193.0.8.0/23
descr: Enterprise 2
origin: AS2
...
Note that AS2 can also decide to originate all routes mentioned so
far, two 24-bit prefixes and one 23-bit prefix. This case would be
represented by storing all three route objects in the database. In
this particular example the additional routes will not add any func-
tionality however and only increase the amount of routes announced
unnecessarily.
Heterogeneous Aggregation
Consider the following case however:
route: 193.0.8.0/24
descr: Enterprise 2
origin: AS2
...
route: 193.0.9.0/24
descr: Enterprise 2 / Special
origin: AS2
comm-list: SPECIAL
...
Now the prefix 193.0.9.0/24 belongs to community SPECIAL (this com-
munity may well not be relevant to routing) and the other prefix
originated by AS2 does not. If AS2 aggregates these prefixes into
the 193.0.8.0/23 prefix, routing policies based on the community
value SPECIAL cannot be implemented in general, because there is no
way to distinguish between the special and the not-so-special parts
of AS2. If another AS has the policy to accept only routes to
members of community SPECIAL it cannot implement it, because accept-
ing the route to 193.0.8.0/23 would also route to 193.0.8.0/24 and
not accepting this route would lose connectivity to the special part
193.0.9.0/24. We call aggregate routes consisting of components
belonging to different communities or even different ASes "hetero-
geneous aggregates".
The problems introduced with heterogeneous aggregates are that once
the homogeneous routes are withdrawn one cannot tell if a more
specific part of the heterogeneous has a different policy. However,
if can be counter argued that knowing this policy is of little use
if you cannot implement a routing policy based on the less specific
(and only route present) heterogeneous aggregate. In fact, this
displays a facet of CIDR itself in that one may actually compromise
slight variations on policy over announcing a larger (albeit
ripe-1nn.txt July, 1994
- 18 -
heterogeneous in terms of policy) aggregate to save address space.
However, it is still useful to be able to document these variations
in policy especially when this homogeneous more specific route is
just being withdrawn. For this one can use the "withdrawn" attri-
bute. The withdrawn attribute can serve to both indicate that a less
specific aggregate is in fact heterogeneous and also allow the gen-
eral documenting of route withdrawal.
So there has to be a way for AS2 to document this even if it does
not originate the route to 193.0.9.0/24 any more. This can be done
with the "withdrawn" attribute of the route object. The aggregate
route to 193.0.8.0/23 is now be registered as:
route: 193.0.8.0/23
descr: Enterprise 2
origin: AS2
...
With the two homogeneous routes marked as withdrawn from the Inter-
net routing mesh but still preserving their original routing infor-
mation.
route: 193.0.8.0/24
descr: Enterprise 2
origin: AS2
withdrawn: 940701
...
route: 193.0.9.0/24
descr: Enterprise 2 / Special
origin: AS2
comm-list: SPECIAL
withdrawn: 940701
...
It should be noted that the date value used in the withdrawn attri-
bute can only be in the past.
Proxy Aggregation
The next step of aggregation are aggregates consisting of more than
one AS. This generally means one AS is aggregating on behalf of
another. It is called proxy aggregation. Proxy aggregation should be
done with great care and always coordinates with other providers
announcing the same route.
Consider the following:
ripe-1nn.txt July, 1994
- 19 -
route: 193.0.0.0/20
descr: All routes known by AS1 in a single package
origin: AS1
...
route: 193.0.1.0/24
descr: Foo
origin: AS1
withdrawn: 940310
...
route: 193.0.8.0/24
descr: Bar
origin: AS2
withdrawn: 940310
...
route: 193.0.9.0/24
descr: Bar-2
origin: AS2
withdrawn: 940310
comm-list: SPECIAL
...
If AS1 announced no other routes to a single homed neighbouring AS,
that neighbour can in general either take that route or leave it but
not differentiate between AS1 and AS2.
Note: If the neighbor was previously configured to accept routes
originating in AS2 but not in AS1 they lose connectivity to AS2 as
well. This means that proxy aggregation has to be done carefully
and in a well coordinated fashion. The information in the withdrawn
route object can help to achieve that.
Aggregates with Holes
If we assume that the world of our example still consists of only
three chunks of address space the aggregate above contains what are
called holes, parts of an aggregate that are not reachable via the
originator of the route. From the routing information itself one
cannot tell whether these are holes and what part of the route falls
inside one. The only way to tell is to send a packet there and see
ripe-1nn.txt July, 1994
- 20 -
whether it gets to the destination, or an ICMP message is received
back, or there is silence. On the other hand announcing aggregates
with holes is quite legitimate. Consider a 16-bit aggregate with
only one 24-bit prefix unreachable. The savings in routing table
size by far outweigh the hole problem.
For operational reasons however it is very useful to register these
holes in the routing registry. Consider the case where a remote net-
work operator experiences connectivity problems to addresses inside
an aggregate route. If the packets are getting to the AS announcing
the aggregate and there are no more specific routes, the normal
cause of action is to get in touch with the originating AS of the
aggregate route and ask them to fix the problem. If the address
falls into a hole this is futile. Therefore problem diagnosis can be
sped up and unnecessary calls prevented by registering the holes in
the routing registry. We do this by using the "hole" attribute. In
our example the representation would be:
route: 193.0.0.0/20
descr: All routes known by AS1
origin: AS1
hole: 193.0.0.0/24
hole: 193.0.2.0/23
hole: 193.0.4.0/22
hole: 193.0.10.0/23
hole: 193.0.12.0/22
...
Note: there would also be two routes with the withdrawn attribute as
displayed above (i.e. 193.0.8.0/24 and 193.0.9.0/24)
Multiple Proxy Aggregation
Finally suppose that AS2 decides to announce the same aggregate,
they would add the following route object to the registry:
route: 193.0.0.0/20
descr: All routes known by AS2
origin: AS2
hole: 193.0.0.0/24
hole: 193.0.2.0/23
hole: 193.0.4.0/22
hole: 193.0.10.0/23
hole: 193.0.12.0/22
...
As per the update procedures below both AS1 and AS2 will be notified
that there already is a route to the same prefix in the registry.
This multiple proxy aggregation is very dangerous to do if the sub-
ripe-1nn.txt July, 1994
- 21 -
aggregates of the route are not the same. It is still dangerous when
the sub-aggregates are consistent but connectivity to the sub-
aggregates varies widely between the originators.
Route object update procedures
Adding a route object will be have to be authorised by the guardian
of the originating AS. The actual implementation of this is outside
the scope of this document. This guarantees that an AS guardian has
full control over the registration of the routes it announces.
What is an Inter-AS network ?
An inter-AS network(3) exists for the purpose of passing traffic and
routing information between different autonomous systems. The most
simple example of an inter-AS network is a point-to-point link, con-
necting exactly two ASes. Each end of such a link is connected to
an interface of router belonging to each of the autonomous systems.
More complex examples are broadcast type networks with multiple
interfaces connecting multiple ASes with the possibility of more
than one connection per AS. Consider the following example of three
routers 1, 2 and 3 with interfaces a through f connected by two
inter-AS networks X and Y:
X Y
a1b --- c2d --- e3f
Suppose that network X is registered in the routing registry as part
of AS1 and net Y as part of AS3. If traffic passes from left to
right prtraceroute will report the following sequence of interfaces
and ASes:
a in AS1
c in AS1
e in AS3
The traceroute algorithm enumerates only the receiving interfaces on
the way to the destination. In the example this leads to the pas-
sage of AS2 going unnoticed. This is confusing to the user and will
also generate exceptions when the path found is checked against the
routing registry.
_________________________
(3) Inter-AS IP networks are those networks are
currently called FIXes, IXFs, DMZs, NAPs, GIX and many
other acronyms.
ripe-1nn.txt July, 1994
- 22 -
For operational monitoring tools such as prtraceroute it is neces-
sary to know which interface on an inter-AS network belongs to which
AS. If AS information is not known about interfaces on an inter-AS
network, tools like prtraceroute cannot determine correctly which
ASes are being traversed.
All interfaces on inter-AS networks will are described in a separate
object know as the `inet-rtr' object [15].
ripe-1nn.txt July, 1994
- 23 -
6. The Autonomous System Object
Autonomous Systems
An Autonomous System (AS) is a group of IP networks run by one or
more network operators which has a single and clearly defined rout-
ing policy.
An AS has a unique number associated with it which is used both in
exchange of exterior routing information and as an identifier of the
AS itself. Exterior routing protocols such as BGP and EGP are used
to exchange routing information between ASes.
In routing terms an AS will normally use one or more interior gate-
way protocols (IGPs) in conjunction with some sort of common agreed
metrics when exchanging network information within its own AS.
The term AS is often confused or even misused as a convenient way of
grouping together a set of networks which belong under the same
administrative umbrella even if within that group of networks there
are various different routing policies. We provide the "community"
concept for such use. ASes can strictly have only one single rout-
ing policy.
The creation of an AS should be done in a conscious and well coordi-
nated manner to avoid creating ASes for the sake of it, perhaps
resulting in the worst case scenario of one AS per routing announce-
ment. It should be noted that there is a limited number of AS
numbers available. Also creating an AS may well increase the number
of AS paths modern EGPs will have to keep track of. This aggravates
what is known as "the routing table growth problem". This may mean
that by applying the general rules for the creation and allocation
of an AS below, some re-engineering may well be needed. However,
this may be the only way to actually implement the desired routing
policy anyway. The creation and allocation of an AS should be done
with the following recommendations in mind:
o Creation of an AS is only required when exchanging routing
information with other ASes. Some router implementations make
use of an AS number as a form of tagging to identify the rout-
ing process. However, it should be noted that this tag does
not need to be unique unless routing information is indeed
exchanged with other ASes.
o For a simple case of customer networks connected to a single
service provider, the IP network should normally be a member of
the service providers AS. In terms of routing policy the IP
network has exactly the same policy as the service provider and
there is no need to make any distinction in routing informa-
tion. This idea may at first seem slightly alien to some, but
it highlights the clear distinction in the use of the AS number
ripe-1nn.txt July, 1994
- 24 -
as a representation of routing policy as opposed to some form
of administrative use.
o If a network operator connects to more than one AS with dif-
ferent routing policies then they need to create their own AS.
In the case of multi-homed customer networks connected to two
service providers there are at least two different routing pol-
icies to a given customer network. At this point the customer
networks will be part of a single AS and this AS would be dis-
tinct from either of the service providers ASes. This allows
the customer the ability of having a different representation
of policy and preference to the different service providers.
This is the ONLY case where a network operator should create
its own AS number.
o As a general rule one should always try to populate the AS with
as many routes as possible, providing all routes conform to the
same routing policy.
Each AS is represented in the RIPE database by both an AS object and
the route objects representing the routes originated by the AS. The
AS object stores descriptive, administrative and contact information
about the AS as well as the routing policies of the AS in relation
to all neighbouring ASes.
The origin attributes of the route objects define the set of routes
originated by the AS. Each route object can have exactly one origin
attribute. Route objects can only be created and updated by the
"guardian" of the AS and not by those immediately responsible for
the particular routes referenced therein. This ensures that opera-
tors, especially service providers, remain in control of AS routing
announcements.
The AS object itself is used to represent a description of adminis-
trative details and the routing policies of the AS itself. The AS
object definition is depicted as follows.
ripe-1nn.txt July, 1994
- 25 -
Example:
aut-num: AS1104
descr: NIKHEF-H Autonomous system
as-in: from AS1213 100 accept AS1213
as-in: from AS1913 100 accept AS1913
as-in: from AS1755 150 accept ANY
as-out: to AS1213 announce ANY
as-out: to AS1913 announce ANY
as-out: to AS1755 announce AS1104 AS1913 AS1213
tech-c: Rob Blokzijl
admin-c: Eric Wassenaar
guardian: as-guardian(a)nikhef.nl
changed: ripe-dbm(a)ripe.net 920910
source: RIPE
See Appendix A for a complete syntax definition of the "aut-num"
object.
It should be noted that this representation provides two things:
o a set of routes.
o a description of administrative details and routing policies.
The set of routes can be used to generate network list based confi-
guration information as well as configuration information for exte-
rior routing protocols knowing about ASes. This means an AS can be
defined and is useful even if it does not use routing protocols
which know about the AS concept.
ripe-1nn.txt July, 1994
- 26 -
Description of routing policies between ASs with multiple connec-
tions - "interas-in/interas-out"
Description of multiple connections between ASs defines how two ASs
have chosen to set different policies for the use of each or some of
the connections between the ASs. This description is necessary only
if the ASs are connected in more than one way and the routing policy
and differs at these two connections.
Example:
LINK1
193.0.1.1 +----------+ 193.0.1.2
| |
AS1------AS2== ==AS3-----AS4
| |
193.0.1.5 +----------+ 193.0.1.6
LINK2
Note: LINK here denotes to connection points between ASs.
It is not necessary just a serial link as it may be inter-
preted. It could be ethernet or other type of connection
as well.
It may be that AS2 wants to use LINK2 only for traffic towards AS4.
LINK1 is used for traffic to AS3 and as backup to AS4, should LINK2
fail. To implement this policy, one would use the attribute
"interas-in" and "interas-out." This attribute permits ASs to
describe their local decisions based on its preference such as
multi-exit-discriminators (MEDs) and to communicate those routing
decisions. This information would be useful in resolving problems
when some traffic paths changed from traversing AS3's gateway in
Timbuktu rather than the gateway in Mogadishu. The exact syntax is
given in Appendix A. However, if we follow this example
through in terms of AS2 we would represent this policy as follows:
Example:
aut-num: AS2
as-in: from AS3 10 accept AS3 AS4
as-out: to AS3 announce AS1 AS2
interas-in: from AS3 193.0.1.1/32 193.0.1.2/32 (pref=5) accept AS3
interas-in: from AS3 193.0.1.1/32 193.0.1.2/32 (pref=15) accept AS4
interas-in: from AS3 193.0.1.5/32 193.0.1.6/32 (pref=10) accept AS4
...
ripe-1nn.txt July, 1994
- 27 -
Here we see additional policy information between two ASs in terms
of the IP addresses of the connection. The parentheses and keyword
are syntactic placeholders to add the readability of the attributes.
If pref=MED is specified the preference indicated by the remote AS
via the multi-exit- discriminator metric such as BGP is used. Of
course this type on inter-AS policy should always be bilaterally
agreed upon to avoid asymmetry and in practice there may need to be
corresponding interas-in attributes in the policy representation of
AS3.
The interas-out attribute is similar in the same way to interas-in
as as-out to as-in. The one major difference being that interas-out
allows to associate an outgoing metric with each route. It is impor-
tant to note that this metric is just passed to the peer AS and it
is at the peer AS's discretion to use or ignore it. A special value
of IGP specifies that the metric passed to the receiving AS will be
derived from the IGP of the sending AS. In this way the peer AS can
choose the optimal link for its traffic as determined by the sending
AS.
When both as-in,as-out and interas-in,interas-out are used, for the
routes mentioned in both set of attributes, the preference defined
in interas-in and interas-out will take precedence for the particu-
lar interas connection point identified by <local-rid> and <remote-
rid>. For the routes which are not mentioned in interas-in and
interas-out, their preference will be using what defined in as-in.
If a route is only referenced in some interas-in/out attributes
and not in others it is assumed not announced/accepted on the con-
nection concerned.
The key difference between interas-in/interas-out and as-in/as-in
attributes is the former describes a more specific inter-AS policy
based on multiple connections between ASs and the latter the general
inter-AS policy. The general policy should always be defined.
The more specific inter-AS policy should only be defined when such a
policy really exists and the implications of setting such poli-
cies are fully understood.
ripe-1nn.txt July, 1994
- 28 -
How to describe the exclusion policy of a certain AS - "as-exclude"
Some ASes have a routing policy based on the exclusion of certain
routes if for whatever reason a certain AS is used as transit.
Whilst, this is in general not good practice as it makes implicit
assumptions on topology with asymmetry a possible outcome if not
coordinated, this case needs to be accommodated within the routing
policy representation.
The way this is achieved is by making use of the "as-exclude" attri-
bute. The precise syntax of this attribute can be found in Appendix
A along with the rest of the defined syntax for the "aut-num"
object. However, some explanation of the use of this attribute is
useful. If we have the following example topology.
Example:
AS4--------AS3
| | |
| | |
AS1--------AS2--------AS5
With a simple corresponding policy like so:
Example:
aut-num: AS1
as-in: from AS2 100 accept ANY
as-out: to AS2 announce AS1
as-exclude: exclude AS4 to ANY
....
We see an interesting policy. What this says in simple terms is AS1
doesn't want to reach anything if it transit AS4. This can be a per-
fectly valid policy. However, it should be realised that for what-
ever reason AS2 decides to route to AS3 via AS4 then immediately AS1
has no connectivity to AS3 or if AS1 is running default to AS2 pack-
ets from AS1 will still flow via AS4. The important point about this
is that whilst AS1 can advise its neighbours of its policy it has no
direct control on how it can enforce this policy to neighbours
upstream.
Another interesting scenario to highlight the unexpected result of
using such an "as-exclude" policy. If we assume in the above example
AS2 preferred AS4 to reach AS3 and AS1 did not use default routing
then as stated AS1 would have no connectivity to AS3. Now lets sup-
pose that for example the link between AS2 and AS4 went down for
some reason. Like so:
ripe-1nn.txt July, 1994
- 29 -
Example:
AS4--------AS3
|
|
AS1--------AS2--------AS5
Suddenly AS1 now has connectivity to AS3. This unexpected behavior
should be considered when created policies based on the "as-exclude"
attribute.
The second problem with this type of policy is the potential of
asymmetry. In the original example we saw the correct policy from
AS1's point of view but if ASes with connectivity through AS4 do not
use a similar policy you have asymmetric traffic and policy. If an
AS uses such a policy they must be aware of the consequences of its
use. Namely that the specified routes which transit the AS (i.e.
routing announcements with this AS in the AS path information) in
question will be excluded. If not coordinated this can easily cause
asymmetry or even worse loss of connectivity to unknown ASes behind
(or in front for that matter) the transit AS in question. With this
in mind this attribute can only be viewed as a form of advisory to
other service providers. However, this does not preclude its use
with policy based tools if the attribute exists.
By having the ability to specify a route keyword based on any of the
four notations given in the syntax it allows the receiving AS to
specify what routes it wishes to exclude through a given transit AS
to a network granularity.
ripe-1nn.txt July, 1994
- 30 -
7. AS Macros
It may be difficult to keep track of each and every new AS that is
represented in the routing registry. A convenient way around this
is to define an `AS Macro' which essentially is a convenient way to
group ASes. This is done so that each and every AS guardian does not
have to add a new AS to it's routing policy as described by the as-
in and as-out attributes of it's AS object.
However, it should be noted that this creates an implicit trust on
the guardian of the AS-Macro.
An AS-Macro can be used in <routing policy expressions> for the
"as-in" and "as-out" attributes in the aut-num object. The AS-Macro
object is then used to derive the list or group of ASes.
A simple example would be something like:
Example:
aut-num: AS786
as-in: from AS1755 100 accept AS-EBONE AND NOT AS1104
as-in: from AS1755 100 accept AS-EBONE AND NOT AS1104
as-out to AS1755 announce AS786
.....
Where the as-macro object for AS-EBONE is as follows:
as-macro: AS-EBONE
descr: ASes routed by EBONE
as-list: AS2121 AS1104 AS2600 AS2122
as-list: AS1103 AS1755 AS2043
guardian: guardian(a)ebone.net
......
So the policy would be evaluated to:
aut-num: AS786
as-in: from AS1755 100 accept (AS2121 OR AS1104 OR AS2600 OR AS2122
as-in: from AS1755 100 accept AS1103 OR AS1755 OR AS2043) AND NOT AS1104
......
It should be noted that the above examples incorporates the rule for
line wrapping as defined in Appendix A for policy lines. See Appen-
dix C for a definition on the AS-Macro syntax.
ripe-1nn.txt July, 1994
- 31 -
8. The Community Object
A community is a group of routes that cannot be represented by an AS
or a group of ASes. It is in some circumstances useful to define a
group of routes that have something in common. This could be a spe-
cial access policy to a supercomputer centre, a group of routes used
for a specific mission, or a disciplinary group that is scattered
among several autonomous systems. Also these communities could be
useful to group routes for the purpose of network statistics.
Communities do not exchange routing information, since they do not
represent an autonomous system. More specifically, communities do
not define routing policies, but access or usage policies. However,
they can de used as in conjunction with an ASes routing policy to
define a set of routes the AS sets routing policy for.
Communities should be defined in a strict manner, to avoid creating
as many communities as there are routes, or even worse. Communities
should be defined following the two rules below;
o Communities must have a global meaning. Communities that have
no global meaning, are used only in a local environment and
should be avoided.
o Communities must not be defined to express non-local policies.
It should be avoided that a community is created because some
other organisation forces a policy upon your organisation.
Communities must only be defined to express a policy defined by
your organisation.
Community examples
There are some clear examples of communities:
BACKBONE -
all customers of a given backbone service provider even though
they can have various different routing policies and hence
belong to different ASes. This would be extremely useful for
statistics collection.
HEPNET -
the High Energy Physics community partly shares infrastructure
with other organisations, and the institutes it consists of are
scattered all over Europe, often being part of a non HEPNET
autonomous system. To allow statistics, access or part of a
routing policy , a community HEPNET, consisting of all routes
that are part of HEPNET, conveniently groups all these routes.
ripe-1nn.txt July, 1994
- 32 -
NSFNET -
the National Science Foundation Network imposes an acceptable
use policy on routes that wish to make use of it. A community
NSFNET could imply the set of routes that comply with this pol-
icy.
MULTI -
a large multinational corporation that does not have its own
internal infrastructure, but connects to the various parts of
its organisations by using local service providers that connect
them all together, may decide to define a community to restrict
access to their networks, only by networks that are part of
this community. This way a corporate network could be defined
on shared infrastructure. Also, this community could be used by
any of the service providers to do statistics for the whole of
the corporation, for instance to do topology or bandwidth plan-
ning.
Similar to Autonomous systems, each community is represented in the
RIPE database by both a community object and community tags on the
route objects representing the routes belonging to the community.
The community object stores descriptive, administrative and contact
information about the community.
The community tags on the route objects define the set of routes
belonging to a community. A route can have multiple community tags.
The community tags can only be created and updated by the "guardian"
of the community and not by those directly responsible for the par-
ticular network. This ensures that guardians remain in control of
community membership.
Here's an example of how this might be represented in terms of the
community tags within the network object. We have an example where
the route 192.16.199.0/24 has a single routing policy (i.e. that of
AS 1104), but is part of several different communities of interest.
We use the tag "comm-list" to represent the list of communities
associated with this route. NIKHEF-H uses the service provider
SURFNET (a service provider with customers with more than one rout-
ing policy), is also part of the High Energy Physics community as
well as having the ability to access the Supercomputer at CERN(4).
_________________________
(4) The community `CERN-SUPER', is somewhat national,
but is intended as an example of a possible use of an
access policy constraint.
ripe-1nn.txt July, 1994
- 33 -
Example:
route: 192.16.199.0/24
descr: Local Ethernet
descr: NIKHEF section H
origin: AS1104
comm-list: HEPNET CERN-SUPER SURFNET
changed: ripe-dbm(a)ripe.net 920604
source: RIPE
In the above examples some communities have been defined. The com-
munity object itself will take the following format:
Example:
community: SURFNET
descr: Dutch academic research network
authority: SURFnet B.V.
guardian: comm-guardian(a)surfnet.nl
admin-c: Erik-Jan Bos
tech-c: Erik-Jan Bos
changed: ripe-dbm(a)ripe.net 920604
source: RIPE
For a complete explanation of the syntax please refer to Appendix B.
ripe-1nn.txt July, 1994
- 34 -
9. Representation of Routing Policies
Routing policies of an AS are represented in the autonomous system
object. Initially we show some examples, so the reader is familiar
with the concept of how routing information is represented, used and
derived. Refer to Appendix A, for the full syntax of the "aut-num"
object.
The topology of routing exchanges is represented by listing how
routing information is exchanged with each neighbouring AS. This is
done separately for both incoming and outgoing routing information.
In order to provide backup and back door paths a relative cost is
associated with incoming routing information.
Example 1:
AS1------AS2
This specifies a simple routing exchange of two presumably isolated
ASes. Even if either of them has routing information about routes
in ASes other than AS1 and AS2, none of that will be announced to
the other.
aut-num: AS1
as-out: to AS2 announce AS1
as-in: from AS2 100 accept AS2
aut-num: AS2
as-out: to AS1 announce AS2
as-in: from AS1 100 accept AS1
The number 100 in the in-bound specifications is a relative cost,
which is used for backup and back door routes. The absolute value is
of no significance. The relation between different values within the
same AS object is. A lower value means a lower cost. This is cons-
ciously similar to the cost based preference scheme used with DNS MX
RRs.
Example 2:
Now suppose that AS2 is connected to one more AS, besides AS1, and
let's call that AS3:
AS1------AS2------AS3
ripe-1nn.txt July, 1994
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In this case there are two reasonable routing policies:
a) AS2 just wants to exchange traffic with both AS1 and AS3 itself
without passing traffic between AS1 and AS3.
b) AS2 is willing to pass traffic between AS3 and AS1, thus acting
as a transit AS
Example 2a:
In the first case AS1's representation in the routing registry will
remain unchanged as will be the part of AS2's representation
describing the routing exchange with AS1. A description of the addi-
tional routing exchange with AS3 will be added to AS2's representa-
tion:
aut-num: AS1
as-out: to AS2 announce AS1
as-in: from AS2 100 accept AS2
aut-num: AS2
as-out: to AS1 announce AS2
as-in: from AS1 100 accept AS1
as-out: to AS3 announce AS2
as-in: from AS3 100 accept AS3
aut-num: AS3
as-out: to AS2 announce AS3
as-in: from AS2 100 accept AS2
Note that in this example, AS2 keeps full control over its
resources. Even if AS3 and AS1 were to allow each others routes in
from AS2, the routing information would not flow because AS2 is not
announcing it(5).
Example 2b:
If contrary to the previous case, AS1 and AS3 are supposed to have
connectivity to each other via AS2, all AS objects have to change:
_________________________
(5) Of course AS1 and AS3 could just send traffic to
each other to AS2 even without AS2 announcing the
routes, hoping that AS2 will forward it correctly. Such
questionable practices however are beyond the scope of
this document.
ripe-1nn.txt July, 1994
- 36 -
aut-num: AS1
as-out: to AS2 announce AS1
as-in: from AS2 100 accept AS2 AS3
aut-num: AS2
as-out: to AS1 announce AS2 AS3
as-in: from AS1 100 accept AS1
as-out: to AS3 announce AS2 AS1
as-in: from AS3 100 accept AS3
aut-num: AS3
as-out: to AS2 announce AS3
as-in: from AS2 100 accept AS1 AS2
Note that the amount of routing information exchanged with a neigh-
bour AS is defined in terms of routes belonging to ASes. In BGP
terms this is the AS where the routing information originates and
the originating AS information carried in BGP could be used to
implement the desired policy. However, using BGP or the BGP AS-path
information is not required to implement the policies thus speci-
fied. Configurations based on route lists can easily be generated
from the database. The AS path information, provided by BGP can
then be used as an additional checking tool as desired.
The specification understands one special expression and this can be
expressed as a boolean expressions:
ANY - means any routing information known. For output this means
that all routes an AS knows about are announced. For input it
means that anything is accepted from the neighbour AS.
ripe-1nn.txt July, 1994
- 37 -
Example 3:
AS4 is a stub customer AS, which only talks to service provider
AS123.
|
|
-----AS123------AS4
|
|
aut-num: AS4
as-out: to AS123 announce AS4
as-in: from AS123 100 accept ANY
aut-num: AS123
as-in: from AS4 100 accept AS4
as-out: to AS4 announce ANY
<further neighbours>
Since AS4 has no other way to reach the outside world than AS123 it
is not strictly necessary for AS123 to send routing information to
AS4. AS4 can simply send all traffic for which it has no explicit
routing information to AS123 by default. This strategy is called
default routing. It is expressed in the routing registry by adding
one or more default tags to the autonomous system which uses this
strategy. In the example above this would look like:
aut-num: AS4
as-out: to AS123 announce AS4
default: AS123 100
aut-num: AS123
as-in: from AS4 100 accept AS4
<further neighbours>
ripe-1nn.txt July, 1994
- 38 -
Example 4:
AS4 now connects to a different operator, AS5. AS5 uses AS123 for
outside connectivity but has itself no direct connection to AS123.
AS5 traffic to and from AS123 thus has to pass AS4. AS4 agrees to
act as a transit AS for this traffic.
|
|
-----AS123------AS4-------AS5
|
|
aut-num: AS4
as-out: to AS123 announce AS4 AS5
as-in: from AS123 100 accept ANY
as-out: to AS5 announce ANY
as-in: from AS5 50 accept AS5
aut-num: AS5
as-in: from AS4 100 accept ANY
as-out: to AS4 announce AS5
aut-num: AS123
as-in: from AS4 100 accept AS4 AS5
as-out: to AS4 announce ANY
<further neighbours>
Now AS4 has two sources of external routing information. AS5 which
provides only information about its own routes and AS123 which pro-
vides information about the external world. Note that AS4 accepts
information about AS5 from both AS123 and AS5 although AS5 informa-
tion cannot come from AS123 since AS5 is connected only via AS4
itself. The lower cost of 50 for the announcement from AS5 itself
compared to 100 from AS123 ensures that AS5 is still believed even
in case AS123 will unexpectedly announce AS5.
In this example too, default routing can be used by AS5 much like in
the previous example. AS4 can also use default routing towards
AS123:
ripe-1nn.txt July, 1994
- 39 -
aut-num: AS4
as-out: to AS123 announce AS4 AS5
default: AS123 11
as-in: from AS5 50 accept AS5
Note no announcements to AS5, they default to us.
aut-num: AS5
as-out: to AS4 announce AS5
default: AS4 100
aut-num: AS123
as-in: from AS4 100 announce AS4 AS5
<further neighbours>
Note that the relative cost associated with default routing is
totally separate from the relative cost associated with in-bound
announcements. The default route will never be taken if an explicit
route is known to the destination. Thus an explicit route can never
have a higher cost than the default route. The relative cost asso-
ciated with the default route is only useful in those cases where
one wants to configure multiple default routes for redundancy.
Note also that in this example the configuration using default
routes has a subtly different behavior than the one with explicit
routes: In case the AS4-AS5 link fails AS4 will send traffic to AS5
to AS123 when using the default configuration. Normally this makes
not much difference as there will be no answer and thus little
traffic. With certain datagram applications which do not require
acknowledgments however, significant amounts of traffic may be use-
lessly directed at AS123. Similarly default routing should not be
used if there are stringent security policies which proscribe any
traffic intended for AS5 to ever touch AS123.
Generally it can be said that default routing should only be used in
very simple topologies. Once the situation gets more complex using
default routes can lead to unexpected results or even defeat the
routing policies established when links fail. As an example consider
how Example 5a) below could be implemented using default routing.
ripe-1nn.txt July, 1994
- 40 -
Example 5:
In a different example AS4 has a private connection to AS6 which in
turn is connected to the service provider AS123:
|
|
-----AS123------AS4
| |
| |
| |
AS6 ---------+
There are a number of policies worth examining in this case:
a) AS4 and AS6 wish to exchange traffic between themselves
exclusively via the private link between themselves; such
traffic should never pass through the backbone (AS123). The
link should never be used for transit traffic, i.e. traffic not
both originating in and destined for AS4 and AS6.
b) AS4 and AS6 wish to exchange traffic between themselves via the
private link between themselves. Should the link fail, traffic
between AS4 and AS6 should be routed via AS123. The link
should never be used for transit traffic.
c) AS4 and AS6 wish to exchange traffic between themselves via the
private link between themselves. Should the link fail, traffic
between AS4 and AS6 should be routed via AS123. Should the
connection between AS4 and AS123 fail, traffic from AS4 to des-
tinations behind AS123 can pass through the private link and
AS6's connection to AS123.
d) AS4 and AS6 wish to exchange traffic between themselves via the
private link between themselves. Should the link fail, traffic
between AS4 and AS6 should be routed via AS123. Should the
backbone connection of either AS4 or AS6 fail, the traffic of
the disconnected AS should flow via the other AS's backbone
connection.
ripe-1nn.txt July, 1994
- 41 -
Example 5a:
aut-num: AS4
as-in: from AS123 100 accept NOT AS6
as-out: to AS123 announce AS4
as-in: from AS6 50 accept AS6
as-out: to AS6 announce AS4
aut-num: AS123
as-in: from AS4 100 accept AS4
as-out: to AS4 announce ANY
as-in: from AS6 100 accept AS6
as-out: to AS6 announce ANY
<further neighbours>
aut-num: AS6
as-in: from AS123 100 accept NOT AS4
as-out: to AS123 announce AS6
as-in: from AS4 50 accept AS4
as-out: to AS4 announce AS6
Note that here the configuration is slightly inconsistent. AS123
will announce AS6 to AS4 and AS4 to AS6. These announcements will be
filtered out on the receiving end. This will implement the desired
policy. Consistency checking tools might flag these cases however.
ripe-1nn.txt July, 1994
- 42 -
Example 5b:
aut-num: AS4
as-in: from AS123 100 accept ANY
as-out: to AS123 announce AS4
as-in: from AS6 50 accept AS6
as-out: AS6 AS4
aut-num: AS123
as-in: AS4 100 AS4
as-out: AS4 ANY
as-in: AS6 100 AS6
as-out: AS6 ANY
<further neighbours>
aut-num: AS6
as-in: from AS123 100 accept ANY
as-out: to AS123 announce AS6
as-in: from AS4 50 accept AS4
as-out: to AS4 announce AS6
The thing to note here is that in the ideal operational case, `all
links working' AS4 will receive announcements for AS6 from both
AS123 and AS6 itself. In this case the announcement from AS6 will
be preferred because of its lower cost and thus the private link
will be used as desired. AS6 is configured as a mirror image.
ripe-1nn.txt July, 1994
- 43 -
Example 5c:
The new feature here is that should the connection between AS4 and
AS123 fail, traffic from AS4 to destinations behind AS123 can pass
through the private link and AS6's connection to AS123.
aut-num: AS4
as-in: from AS123 100 accept ANY
as-out: to AS123 announce AS4
as-in: from AS6 50 accept AS6
as-in: from AS6 110 accept ANY
as-out: to AS6 AS4
aut-num: AS123
as-in: from AS4 1 accept AS4
as-out: to AS4 announce ANY
as-in: from AS6 1 accept AS6
as-in: from AS6 2 accept AS4
as-out: to AS6 announce ANY
<further neighbours>
aut-num: AS6
as-in: from AS123 100 accept ANY
as-out: to AS123 AS6 announce AS4
as-in: from AS4 50 accept AS4
as-out: to AS4 announce ANY
Note that it is important to make sure to propagate routing informa-
tion for both directions in backup situations like this. Connec-
tivity in just one direction is not useful at all for almost all
applications.
Note also that in case the AS6-AS123 connection breaks, AS6 will
only be able to talk to AS4. The symmetrical case (5d) is left as an
exercise to the reader.
10. Future Extensions
We envision that over time the requirements for describing routing
policy will evolve. The routing protocols will evolve to support the
requirements and the routing policy description syntax will need to
evolve as well. For that purpose, a separate document will describe
experimental syntax definitions for policy description. This docu-
ment will be updated when new objects or attributes are proposed or
modified.
Two new attributes of the AS object which are proposed and supported
by the Merit Routing Registry are as-transit and db-selector.
as-transit describes the transit preferences of an AS. It allows an
AS to describe its path preference in order to reach certain
ripe-1nn.txt July, 1994
- 44 -
destinations. The AS(s) specified in the path preference may or may
not be an immediate neighbor of the AS defined in the AS object.
as-transit accommodates policy decisions involving AS path whereas
as-in and as-out do not. It is not unusual for ASs to have routing
policies which involve path selection based on AS. Emerging proto-
cols like SDRP [13] will allow an AS to choose a path independent of
a neighboring ASs path choice. as-transit permits descriptions based
on AS path selection.
The DataBase Selector (db-selector) function allows one to take
advantage of information registered in other Registries. It permits
the selection of networks in a database based on their attributes.
It is proposed to be used within the as-in/as-out attribute family
to make the description of policy concise. For example, if an AS
has the policy of not accepting any routes from country XYZ, the AS
can use the db-selector to check a database which has a network and
country attribute and relate that information to the information in
the routing registry. The advantage of referencing another database
is that the routing registry will avoid duplicating the information
maintained in other information registries.
Detailed examples and syntax are described in document ???? [14].
ripe-1nn.txt July, 1994
- 45 -
11. References
[1] Bates, T., Jouanigot, J-M., Karrenberg, D., Lothberg, P.,
Terpstra, M., "Representation of IP Routing Policies in the
RIPE Database", RIPE-81, February 1993.
[2] Merit Network Inc.,"Representation of Complex Routing Policies
of an Autonomous System", DRAFT, March, 1994.
[3] PRIDE Tools Release 1.
See ftp.ripe.net:pride/tools/pride-tools-1.tar.Z.
[4] Merit Inc. RRDB Tools.
See rrdb.merit.edu:pub/meritrr/*
[5] The Network List Compiler.
See dxcoms.cern.ch:pub/ripe-routing-wg/nlc-2.2d.tar
[6] Lord, A., Terpstra, M., "RIPE Database Template for Networks
and Persons", DRAFT, May 1994.
[7] Karrenberg, D., "RIPE Database Template for Domains", RIPE-49,
April 1992.
[8] Lougheed, K., Rekhter, Y., "A Border Gateway Protocol 3 (BGP-
3)", RFC1267, October 1991.
[9] Rekhter, Y., Li, T., "A Border Gateway Protocol 4 (BGP-4)",
RFC-1654, May 1994.
[10] Bates, T., Karrenberg, D., Terpstra, M., "Support for Classless
Internet Addresses in the RIPE Database", DRAFT, May 1994.
[11] Karrenberg, D., "Authorisation and Notification of Changes in
the RIPE Database", RIPE-96, October 1993.
[12] Bates, T., "Support of Guarded fields within the RIPE Data-
base", ripe-108, February 1994.
[13] Estrin, D., Li, T., Rekhter, Y., Varadhan, K., "Source Demand
Routing: Packet Format and Forwarding Specification (Version
1)", INTERNET-DRAFT, draft-ietf-sdr-sdrp-04.txt, March 1994.
[14] ?????, "Experimental Objects and attributes for the Routing
Registry, ???, ????.
[15] Bates, T., "Specifying an `Internet Router' in the Routing
Registry", DRAFT, July 1994.
ripe-1nn.txt July, 1994
- 46 -
12. Author's Addresses
Tony Bates
RARE/PRIDE Project
c/o RIPE Network Coordination Centre
Kruislaan 409
NL-1098 SJ Amsterdam
The Netherlands
+31 20 592 5064
T.Bates(a)ripe.net
Elise Gerich
The University of Michigan
Merit Computer Network
1075 Beal Avenue
Ann Arbor, MI 48109
USA
+1 313 936 2120
epg(a)merit.edu
Laurent Joncheray
The University of Michigan
Merit Computer Network
1075 Beal Avenue
Ann Arbor, MI 48109
USA
+1 313 936 2065
lpj(a)merit.edu
Jean-Michel Jouanigot
CERN, European Laboratory for Particle Physics
CH-1211 Geneva 23
Switzerland
+41 22 767 4417
Jean-Michel.Jouanigot(a)cern.ch
Daniel Karrenberg
RIPE Network Coordination Centre
Kruislaan 409
NL-1098 SJ Amsterdam
The Netherlands
+31 20 592 5065
D.Karrenberg(a)ripe.net
ripe-1nn.txt July, 1994
- 47 -
Marten Terpstra
PRIDE Project
c/o RIPE Network Coordination Centre
Kruislaan 409
NL-1098 SJ Amsterdam
The Netherlands
+31 20 592 5064
M.Terpstra(a)ripe.net
Jessica Yu
The University of Michigan
Merit Computer Network
1075 Beal Avenue
Ann Arbor, MI 48109
USA
+1 313 936 2655
jyy(a)merit.edu
ripe-1nn.txt July, 1994
- 48 -
Appendix A - Syntax for the aut-num object.
Here is a summary of the tags associated with aut-num object itself
and their status. The first column specifies the attribute, the
second column whether this attribute is mandatory in the aut-num
object, and the third column whether this specific attribute can
occur only once per object [single], or more than once [multiple].
When specifying multiple lines per attribute, the attribute name
must be repeated. See [6] the example for the descr: attribute.
aut-num: [mandatory] [single]
descr: [mandatory] [multiple]
as-in: [optional] [multiple]
as-out: [optional] [multiple]
interas-in: [optional] [multiple]
interas-out: [optional] [multiple]
as-exclude: [optional] [multiple]
default: [optional] [multiple]
tech-c: [mandatory] [multiple]
admin-c: [mandatory] [multiple]
guardian: [mandatory] [single]
remarks: [optional] [multiple]
notify: [optional] [multiple]
maintainer: [optional] [single]
changed: [mandatory] [multiple]
source: [mandatory] [single]
Each attribute has the following syntax:
aut-num:
The autonomous system number. This must be a uniquely allo-
cated autonomous system number from an AS registry (i.e. the
RIPE NCC, the Inter-NIC, etc).
Format:
AS<positive integer between 1 and 65535>
Example:
aut-num: AS1104
Status: mandatory, only one line allowed
descr:
A short description of the Autonomous System.
Format:
free text
Status: mandatory, multiple lines allowed
as-in:
ripe-1nn.txt July, 1994
- 49 -
Example:
descr: NIKHEF section H
descr: Science Park Watergraafsmeer
descr: Amsterdam
A description of accepted routing information between AS peers.
Format:
from <aut-num> <cost> accept <routing policy expression>
The keywords from and accept are optional and can be omit-
ted.
<aut-num> refers to your AS neighbour.
<cost> is a positive integer used to express a relative
cost of routes learned. The lower the cost the more pre-
ferred the route.
<routing policy expression> can take the following for-
mats.
1. A list of one or more ASes, AS Macros, Communities or
Network Lists.
A Network List is a list of network numbers in prefix
length format, separated by commas, and surrounded by
curly brackets.
Examples:
as-in: from AS1103 100 accept AS1103
as-in: from AS786 105 accept AS1103
as-in: from AS786 10 accept AS786 HEPNET
as-in: from AS1755 110 accept AS1103 AS786
as-in: from AS3333 100 accept {192.87.45.0/16, 128.141.0.0/16}
2. A set of KEYWORDS. The following KEYWORD is
currently defined:
ANY this means anything the neighbour AS knows.
3. A logical expression of either 1 or 2 above The
current logical operators are defined as:
AND
OR
NOT
ripe-1nn.txt July, 1994
- 50 -
NOTE: if no logical operator is given between ASes,
AS-macros, Communities, Network Lists and KEYWORDS it
is implicitly evaluated as an `OR' operation. The OR
can be left out for conciseness.
Rules are grouped together using parenthesis i.e "("
and ")".
Example:
as-in: from AS1755 100 accept ANY AND NOT (AS1234 OR AS513)
as-in: from AS1755 150 accept AS1234 OR {35.0.0.0/8}
A rule can be wrapped over lines providing the
associated <aut-num>, <cost> values and from and
accept keywords are repeated and occur on con-
secutive lines.
Example:
as-in: from AS1755 100 accept ANY AND NOT (AS1234 AS513)
and
as-in: from AS1755 100 accept ANY AND NOT (
as-in: from AS1755 100 accept AS1234 AS513)
are evaluated to the same result. Please note
that the ordering of these continuing lines
matters.
Status: optional, multiple lines allowed
as-out:
A description of generated routing information sent to other AS
peers.
Format:
to <aut-num> announce <routing policy expression
The to and announce keywords are optional and can be omit-
ted.
<aut-num> refers to your AS neighbour.
<routing policy expression> is explained in the as-in
attribute definition above.
Example:
as-out: to AS1104 announce AS978
as-out: to AS1755 announce ANY
as-out: to AS786 announce ANY AND NOT (AS978)
Status: optional, multiple lines allowed
ripe-1nn.txt July, 1994
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interas-in:
Describes incoming local preferences on an inter AS connection.
Format:
from <aut-num> [<local-rid>] [<neighbor-rid>] <preference>
accept <routing policy expression>
The keywords from and accept are optional and can be omit-
ted.
<aut-num> is an autonomous system as defined in as-in.
<local-rid> contains the IP address of the border router
in the AS describing the policy. IP address must be in
prefix length format. This field is optional.
<neighbor-rid> contains the IP address of neighbor AS's
border router from which this AS accept routes defined in
the <routing policy expression>. IP addresses must be in
prefix length format. This field is optional.
<local-info> contains the IP address of the local border
router, followed by a space, followed by the IP address of
the remote border router. IP addresses must be in prefix
length format.
<preference> is defined as follows:
(<pref-type>=<value>)
It should be noted the parenthesis ``('' and ``)'' and the
``<pref-type>'' keyword must be present for this prefer-
ence to be valid.
<pref-type> currently only supports "pref". It could be
expanded to other type of preference such as tos/qos as
routing technology matures.
<value> can take one of the following values:
<cost>
<cost> is a positive integer used to express a rela-
tive cost of routes learned. The lower the cost the
more preferred the route. This <cost> value is only
relevant to other interas-in attributes, not to as-in
attributes.
MED
This indicates the AS will use the MED metric, as
implemented in BGP, sent from its neighbor AS.
NOTE: Combinations of MED and <cost> should be
avoided for the same destinations.
ripe-1nn.txt July, 1994
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CAVEAT: The pref-type values may well be enhanced in
the future as more inter-ASs routing protocols intro-
duce other metrics.
<routing policy expression> is an expression as defined in
as-in above.
Examples:
interas-in: from AS1104 192.87.45.254/32 192.87.45.80/32 (pref=10) accept AS786 AS987
interas-in: from AS1104 192.87.45.254/32 192.87.45.79/32 (pref=20) accept AS987
interas-in: from AS1103 192.87.45.254/32 192.87.45.32/32 (pref=MED) accept ANY
Status: optional, multiple lines allowed
interas-out:
Format:
to <aut-num> [<local-rid>] [<neighbor-rid>] announce
[<metric>] <routing policy expression>
The keywords to and announce are optional and can be omit-
ted.
The definitions of <aut-num>, <local-rid> <neighbor-rid>,
and <routing policy expression> are identical to those
defined in interas-in.
<metric> is defined as follows:
(<metric-type>=<value>)
It should be noted the parenthesis ``('' and ``)'' and the
keywords of ``<metric-type>'' must be present for this
metric to be valid.
<metric-type> currently only supports "metric-out". It
could be expanded to other type of preference such as
tos/qos as routing technology matures.
<value> can take one of the following values:
<num-metric>
<num-metric> is a pre-configured metric for outbound
routes. The lower the cost the more preferred the
route. This <num-metric> value is only relevant to
other interas-out attributes, not to as-out attri-
butes.
IGP
This indicates that this means that the metric
reflects the ASs internal topology cost. The topology
is reflected here by using MED which is derived from
the AS's IGP metric.
ripe-1nn.txt July, 1994
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NOTE: Combinations of IGP and <num-metric> should be
avoided for the same destinations.
CAVEAT: The metric-out values may well be enhanced in
the future as more interas protocols make use of
metrics.
Examples:
interas-out: to AS1104 192.87.45.254/32 192.87.45.80/32 (metric-out=10) announce AS23 AS10
interas-out: to AS1104 192.87.45.80/32 (metric-out=15) announce AS10
interas-out: to AS1103 192.87.45.254/32 (metric-out=IGP) announce ANY
Status: optional, multiple lines allowed
as-exclude:
A list of transit ASes to ignore all routes from.
Format:
exclude <aut-num> to <exclude-route-keyword>
Keywords exclude and to are optional and can again be
omitted.
<aut-num> refers to the transit AS in question.
an <exclude-route-keyword> can be ONE of the following.
1. <aut-num>
2. AS macro
3. Community
4. ANY
Examples:
as-exclude: exclude AS690 to HEPNET
This means exclude any HEPNET routes which have a route
via AS690.
as-exclude: exclude AS1800 to AS-EUNET
This means exclude any AS-EUNET routes which have a route
via AS1800.
as-exclude: exclude AS1755 to AS1104
This means exclude any AS1104 route which have a route via
AS1755.
ripe-1nn.txt July, 1994
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as-exclude: exclude AS1104 to ANY
This means exclude all routes which have a route via
AS1104.
Status: optional, multiple lines allowed
default:
An indication of how default routing is done.
Format:
<aut-num> <relative cost> <default-expression>
where <aut-num> is the AS peer you will default route to,
and <relative cost> is the relative cost is a positive
integer used to express a preference for default. There is
no relationship to the cost used in the as-in tag. The AS
peer with the lowest cost is used for default over ones
with higher costs.
<default-expression> is optional and provides information
on how a default route is selected. It can take the fol-
lowing formats:
1. static. This indicates that a default is statically
configured to this AS peer.
2. A network list with the syntax as described in the
as-in attribute. This indicates that this list of
routes is used to generate a default route. A special
but valid value in this is the special route used by
some routing protocols to indicate default: 0.0.0.0/0
3. default. This is the same as {0.0.0.0/0}. This means
that the routing protocol between these two peers
generates a true default.
Examples:
default: AS1755 10
default: AS786 5 {140.222.0.0/16, 192.87.45.0/24}
default: AS2043 15 default
Status: optional, multiple lines allowed
tech-c:
Full name or uniquely assigned NIC-handle of a technical con-
tact person. This is someone to be contacted for technical
problems such as misconfiguration.
Format:
<firstname> <initials> <lastname> or <nic-handle>
ripe-1nn.txt July, 1994
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Example:
tech-c: John E Doe
tech-c: JED31
Status: mandatory, multiple lines allowed
admin-c:
Full name or uniquely assigned NIC-handle of an administrative
contact person. In many cases this would be the name of the
guardian.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Example:
admin-c: Joe T Bloggs
admin-c: JTB1
Status: mandatory, multiple lines allowed
guardian:
Mailbox of the guardian of the Autonomous system.
Format:
<email-address>
The <email-address> should be in RFC822 domain format
wherever possible.
Example:
guardian: as1104-guardian(a)nikhef.nl
Status: mandatory, only one line and e-mail address allowed
remarks:
Remarks/comments, to be used only for clarification.
Format:
free text
Example:
remarks: Multihomed AS talking to AS1755 and AS786
remarks: Will soon connect to AS1104 also.
Status: optional, multiple lines allowed
notify:
The notify attribute contains an email address to which notifi-
cations of changes to this object should be sent. See also
[11].
ripe-1nn.txt July, 1994
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Format:
<email-address>
The <email-address> should be in RFC822 domain syntax
wherever possible.
Example:
notify: Marten.Terpstra(a)ripe.net
Status: optional, multiple lines allowed
maintainer:
The maintainer attribute contains a registered maintainer name.
See also [11].
Format:
<registered maintainer name>
Example:
maintainer: RIPE-DBM
Status: optional, multiple lines allowed
changed:
Who changed this object last, and when was this change made.
Format:
<email-address> YYMMDD
<email-address> should be the address of the person who
made the last change. YYMMDD denotes the date this change
was made.
Example:
changed: johndoe(a)terabit-labs.nn 900401
Status: mandatory, multiple lines allowed
source:
Source of the information.
This is used to separate information from different sources
kept by the same database software. For RIPE database entries
the value is fixed to RIPE.
Format:
RIPE
Status: mandatory, only one line allowed
ripe-1nn.txt July, 1994
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Appendix B - Syntax details for the community object.
Here is a summary of the tags associated with community object
itself and their status. The first column specifies the attribute,
the second column whether this attribute is mandatory in the commun-
ity object, and the third column whether this specific attribute can
occur only once per object [single], or more than once [multiple].
When specifying multiple lines per attribute, the attribute name
must be repeated. See [6] the example for the descr: attribute.
community: [mandatory] [single]
descr: [mandatory] [multiple]
authority: [mandatory] [single]
guardian: [mandatory] [single]
tech-c: [mandatory] [multiple]
admin-c: [mandatory] [multiple]
remarks: [optional] [multiple]
notify: [optional] [multiple]
maintainer: [optional] [single]
changed: [mandatory] [multiple]
source: [mandatory] [single]
Each attribute has the following syntax:
community:
Name of the community. The name of the community should be
descriptive of the community it describes.
Format:
Upper case text string which cannot start with "AS" or any
of the <routing policy expression> KEYWORDS. See Appendix
A.
Example:
community: WCW
Status: mandatory, only one line allowed
descr:
A short description of the community represented.
Format:
free text
Example:
descr: Science Park Watergraafsmeer
descr: Amsterdam
Status: mandatory, multiple lines allowed
ripe-1nn.txt July, 1994
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authority:
The formal authority for this community. This could be an
organisation, institute, committee, etc.
Format:
free text
Example:
authority: WCW LAN Committee
Status: mandatory, only one line allowed
guardian:
Mailbox of the guardian of the community.
Format:
<email-address>
The <email-address> should be in RFC822 domain format
wherever possible.
Example:
guardian: wcw-guardian(a)nikhef.nl
Status: mandatory, only one line and email address allowed
tech-c:
Full name or uniquely assigned NIC-handle of an technical con-
tact person for this community.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Example:
tech-c: John E Doe
tech-c: JED31
Status: mandatory, multiple lines allowed
admin-c:
Full name or uniquely assigned NIC-handle of an administrative
contact person. In many cases this would be the name of the
guardian.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Example:
admin-c: Joe T Bloggs
admin-c: JTB1
ripe-1nn.txt July, 1994
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Status: mandatory, multiple lines allowed
remarks:
Remarks/comments, to be used only for clarification.
Format:
free text
Example:
remarks: Temporary community
remarks: Will be removed after split into ASes
Status: optional, multiple lines allowed
notify:
The notify attribute contains an email address to which notifi-
cations of changes to this object should be send. See also
[11].
Format:
<email-address>
The <email-address> should be in RFC822 domain syntax
wherever possible.
Example:
notify: Marten.Terpstra(a)ripe.net
Status: optional, multiple lines allowed
maintainer:
The maintainer attribute contains a registered maintainer name.
See also [11].
Format:
<registered maintainer name>
Example:
maintainer: RIPE-DBM
Status: optional, multiple lines allowed
changed:
Who changed this object last, and when was this change made.
Format:
<email-address> YYMMDD
<email-address> should be the address of the person who
made the last change. YYMMDD denotes the date this change
was made.
ripe-1nn.txt July, 1994
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Example:
changed: johndoe(a)terabit-labs.nn 900401
Status: mandatory, multiple lines allowed
source:
Source of the information.
This is used to separate information from different sources
kept by the same database software. For RIPE database entries
the value is fixed to RIPE.
Format:
RIPE
Status: mandatory, only one line allowed
ripe-1nn.txt July, 1994
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Appendix C - AS Macros syntax definition.
Here is a summary of the tags associated with as-macro object itself
and their status. The first column specifies the attribute, the
second column whether this attribute is mandatory in the as-macro
object, and the third column whether this specific attribute can
occur only once per object [single], or more than once [multiple].
When specifying multiple lines per attribute, the attribute name
must be repeated. See [6] the example for the descr: attribute.
as-macro: [mandatory] [single]
descr: [mandatory] [multiple]
as-list: [mandatory] [multiple]
guardian: [mandatory] [single]
tech-c: [mandatory] [multiple]
admin-c: [mandatory] [multiple]
remarks: [optional] [multiple]
notify: [optional] [multiple]
maintainer: [optional] [single]
changed: [mandatory] [multiple]
source: [mandatory] [single]
Each attribute has the following syntax:
as-macro:
The name of a macro containing at least two Autonomous Systems
grouped together for ease of administration.
Format:
AS-<string>
The <string> should be in upper case and not contain any
special characters.
Example:
as-macro: AS-EBONE
Status: mandatory, only one line allowed
descr:
A short description of the Autonomous System Macro.
Format:
free text
Example:
descr: Macro for EBONE connected ASes
Status: mandatory, multiple lines allowed
ripe-1nn.txt July, 1994
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as-list:
The list of ASes that make up this macro.
Format:
<aut-num> <aut-num> ...
See Appendix A for <aut-num> definition.
Example:
as-list: AS786 AS513 AS1104
Status: mandatory, multiple lines allowed
guardian:
Mailbox of the guardian of this AS macro.
Format:
<email-address>
The <email-address> should be in RFC822 domain format
wherever possible.
Example:
guardian: as-ebone-guardian(a)ebone.net
Status: mandatory, only one line and e-mail address allowed
tech-c:
Full name or uniquely assigned NIC-handle of a technical con-
tact person for this macro. This is someone to be contacted for
technical problems such as misconfiguration.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Examples:
tech-c: John E Doe
tech-c: JED31
Status: mandatory, multiple lines allowed
admin-c:
Full name or uniquely assigned NIC-handle of an administrative
contact person. In many cases this would be the name of the
guardian.
Format:
<firstname> <initials> <lastname> or <nic-handle>
Examples:
ripe-1nn.txt July, 1994
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admin-c: Joe T Bloggs
admin-c: JTB1
Status: mandatory, multiple lines allowed
remarks:
Remarks/comments, to be used only for clarification.
Format:
free text
Example:
remarks: AS321 will be removed from this Macro shortly
Status: optional, multiple lines allowed
notify:
The notify attribute contains an email address to which notifi-
cations of changes to this object should be send. See also
[11].
Format:
<email-address>
The <email-address> should be in RFC822 domain syntax
wherever possible.
Example:
notify: Marten.Terpstra(a)ripe.net
Status: optional, multiple lines allowed
maintainer:
The maintainer attribute contains a registered maintainer name.
See also [11].
Format:
<registered maintainer name>
Example:
maintainer: RIPE-DBM
Status: optional, multiple lines allowed
changed:
Who changed this object last, and when was this change made.
Format:
<email-address> YYMMDD
ripe-1nn.txt July, 1994
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<email-address> should be the address of the person who
made the last change. YYMMDD denotes the date this change
was made.
Example:
changed: johndoe(a)terabit-labs.nn 900401
Status: mandatory, multiple lines allowed
source:
Source of the information.
This is used to separate information from different sources
kept by the same database software. For RIPE database entries
the value is fixed to RIPE.
Format:
RIPE
Status: mandatory, only one line allowed
ripe-1nn.txt July, 1994
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Appendix D - Syntax for the "route" object.
There is a summary of the tags associated with community object
itself and their status. The first column specifies the attribute,
the second column whether this attribute is mandatory in the commun-
ity object, and the third column whether this specific attribute can
occur only once per object [single], or more than once [multiple].
When specifying multiple lines per attribute, the attribute name
must be repeated. See [6] the example for the descr: attribute.
route: [mandatory] [single]
descr: [mandatory] [multiple]
origin: [mandatory] [single]
hole: [optional] [multiple]
withdrawn: [optional] [multiple]
comm-list: [optional] [multiple]
remarks: [optional] [multiple]
notify: [optional] [multiple]
maintainer: [optional] [single]
changed: [mandatory] [multiple]
source: [mandatory] [single]
Each attribute has the following syntax:
route:
Route being announced.
Format:
Classless representation of a route with the RIPE database
known as the "prefix length" representation. See [10] for
more details on classless representations.
Examples:
route: 192.87.45.0/24
This represents addressable bits 192.87.45.0 to
192.87.45.255.
route: 192.1.128.0/17
This represents addressable bits 192.1.128.0 to
192.1.255.255.
Status: mandatory, only one line allowed
origin:
The autonomous system announcing this route.
Format:
<aut-num>
ripe-1nn.txt July, 1994
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See appendix A for <aut-num> syntax.
Example:
origin: AS1104
Status: mandatory, only one line allowed
hole:
Denote the parts of the address space covered this route object
to which the originator does not provide connectivity.
Format:
Classless representation of a route with the RIPE database
known as the "prefix length" representation. See [10] for
more details on classless representations. It should be
noted that is sub-aggregate must be a component of that
registered in the route object.
Example:
hole: 193.0.4.0/24
Status: optional, multiple lines allowed
withdrawn:
Used to denote the day this route has been withdrawn from the
Internet routing mesh. It should be noted that this date cannot
be in the future.
Format:
YYMMDD
YYMMDD denotes the date this route was withdrawn.
Example:
withdrawn: 940711
Status: optional, multiple lines allowed
comm-list:
List of one or more communities this route is part of.
Format:
<community> <community> ...
See Appendix B for <community> definition.
Example:
comm-list: HEP LEP
Status: optional, multiple lines allowed
ripe-1nn.txt July, 1994
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remarks:
Remarks/comments, to be used only for clarification.
Format:
free text
Example:
remarks: Multihomed AS talking to AS1755 and AS786
remarks: Will soon connect to AS1104 also.
Status: optional, multiple lines allowed
notify:
The notify attribute contains an email address to which notifi-
cations of changes to this object should be send. See also
[11].
Format:
<email-address>
The <email-address> should be in RFC822 domain syntax
wherever possible.
Example:
notify: Marten.Terpstra(a)ripe.net
Status: optional, multiple lines allowed
maintainer:
The maintainer attribute contains a registered maintainer name.
See also [11].
Format:
<registered maintainer name>
Example:
maintainer: RIPE-DBM
Status: optional, multiple lines allowed
changed:
Who changed this object last, and when was this change made.
Format:
<email-address> YYMMDD
<email-address> should be the address of the person who
made the last change. YYMMDD denotes the date this change
was made.
Example:
ripe-1nn.txt July, 1994
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changed: johndoe(a)terabit-labs.nn 900401
Status: mandatory, multiple lines allowed
source:
Source of the information.
This is used to separate information from different sources
kept by the same database software. For RIPE database entries
the value is fixed to RIPE.
Format:
RIPE
Status: mandatory, only one line allowed
ripe-1nn.txt July, 1994
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Appendix E - List of reserved words
The following list of words are reserved for use within the attri-
butes of the AS object. The use of these words is solely for the
purpose of clarity. All keywords must be lower case.
accept
announce
exclude
from
to
transit
Examples of the usage of the reserved words are:
as-in: from neighborAS accept route
as-out: to neighborAS announce route
as-exclude: exclude ASpath to destination
as-transit: transit ASpath to destination
default: from neighborAS accept route
default: to neighborAS announce route
Note: that as-transit is an experimental attribute. See section 10.
ripe-1nn.txt July, 1994
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Appendix F - Motivations for RIPE-81++
This appendix gives motivations for the major changes in this propo-
sal from ripe-81. (It is not complete yet).
The main goals of the routing registry rework are:
SPLIT
Separate the allocation and routing registry functions into
different database objects. This will facilitate data manage-
ment if the Internet registry and routing registry functions
are separated (like in other parts of the world). It will also
make more clear what is part of the routing registry and who
has authority to change allocation vs. routing data.
CIDR
Add the possibility to specify classless routes in the routing
registry. Classless routes are being used in Internet produc-
tion now. Aggregation information in the routing registry is
necessary for network layer troubleshooting. It is also neces-
sary because aggregation influences routing policies directly.
CALLOC
Add the possibility to allocate address space on classless
boundaries in the allocation registry. This is a way to
preserve address space.
CLEAN
To clean up some of the obsolete and unused parts of the rout-
ing registry.
The major changes are now discussed in turn:
Introduce Classless Addresses
CIDR, CALLOC
Introduce route object.
SPLIT, CIDR and CALLOC.
Delete obsolete attributes from inetnum.
CLEAN.
ripe-1nn.txt July, 1994
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Delete RIPE-DB and LOCAL from routing policy expressions.
CLEAN
Allow multiple ASes to originate the same route
Because it is being done. CIDR. Made possible by SPLIT.
ripe-1nn.txt July, 1994
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Appendix G - Transition strategy from RIPE-81 to RIPE-81++
Transition from the routing registry described by ripe-81 to the
routing registry described in this document is a straightforward
process once the new registry functions have been implemented in the
database software and are understood by the most commonly used
registry tools. The routing related attributes in the classful inet-
num objects of ripe-81 can be directly translated into new routing
objects. Then these attributes can be deleted from the inetnum
object making that object conform to the new schema.
Proposed transition steps:
1) Implement classless addresses and new object definition in the
database software.
2) Make common tools understand the new schema and prefer it if
both old and new are present.
3) Invite everyone to convert their data to the new format. This
can be encouraged by doing conversions automatically and pro-
posing them to maintainers.
4) At a flag day remove all remaining routing information from the
inetnum objects. Before the flag day all usage of obsoleted
inetnum attributes has to cease and all other routing registry
functions have to be taken over by the new objects and attri-
butes.
The current estimate is that point three can be reached in the Sum-
mer 1994 if the draft is accepted by mid-June. The flag day should
be scheduled 3-4 months after this point.
ripe-1nn.txt July, 1994
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