Friends,
here is the proposal on how to solve the prtraceroute problem as
discussed in the last routing-WG meeting. Could we have comments until
May 17th please! I'll circulate new versions as substantive comments
are incorporated. The goal is to have the database capable of storing this
a.s.a.p. and have some data in there quickly as prtraceroute is released.
Note that this is not only useful for prtraceroute but much more generally.
It could also be the start of the local inter-AS connection information
dicussed in the last routing-wg meeting too. As such this addendum could
be extended. Proposals ?
Cheers
Daniel
Description of Inter-AS Networks in the RIPE
Routing Registry
Tony Bates
Daniel Karrenberg
Addendum to
Representation of IP Routing Policies
in the RIPE Database (ripe-81)
What is an Inter-AS Network ?
Inter-AS IP networks are those networks which connect multi-
ple autonomous systems (1). An inter-AS network exists for
the purpose of passing traffic and routing information
between different autonomous systems. The most simple exam-
ple of an inter-AS network is a point-to-point link, con-
necting exactly two ASes. Each end of such a link is con-
nected to an interface of router living in each of the auto-
nomous systems. More complex examples are broadcast type
networks with multiple interfaces connecting multiple ASes
with the possibility of more than one connection per AS.
Which additional information is needed?
Consider the following example of three routers 1, 2 and 3
with interfaces a through f connected by two inter-AS net-
works X and Y:
X Y
a1b --- c2d --- e3f
_________________________
(1) Inter-AS networks are currently called FIXes, IXFs,
DMZs, NAPs, GIX and other names.
- 2 -
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 passage 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.
For operational monitoring tools such as prtraceroute it is
necessary 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.
Proposed Format
All interfaces on inter-AS networks will be described in a
new ias-int attribute of the corresponding network object in
the RIPE database. The ias-int attribute has the following
syntax:
ias-int: <interface-address> <autonomous-system>
The <interface-address> must be an address within the
corresponding intenum and <autonomous-system> must be of the
form AS<number> refering to an aut-num object in the data-
base.
- 3 -
For example:
inetnum: 193.193.193.0
netname: INTER-AS-EXAMPLE
descr: This is a hypothetical inter-as network.
descr: It might be called a NAP, FIX, GIX, IXF, DMZ,
descr: Mehrfachdienstanbieterkommunikationseinrichtung or ...
country: DE
admin-c: Werner Mueller
tech-c: Paul Schmitz
tech-c: Hans Meier
changed: ripe-dbm(a)ripe.net 920714
aut-sys: AS4711
ias-int: 193.193.193.1 AS123
ias-int: 193.193.193.3 AS4711
ias-int: 193.193.193.9 AS789
source: RIPE
Note that the interface 193.193.193.3 is described although
it is in the same AS as the network. This is recommended
practice.
The update procedure for the ias-int attribute will be the
normal update procedure for network objects. The attribute
does not need to be guarded because it does not influence
routing policy of operational traffic.
In which AS does an Inter-AS Network belong?
Only one AS announces an inter-AS network externally. The
other ASes connected to the inter-AS network will probably
carry this network in their internal routing for redundancy
but will not announce it to other ASes.
In exceptional cases more than one AS may need to originate
external routing information about the inter-AS network,
This kind of routing setup cannot be described within the
framework of ripe-81 and is generally discouraged. Tools
using a ripe-81 type registry could take heuristic hints
from the ias-int attributes when they encounter such situa-
tions.