- db-wg - mailman.ripe.net

Possible addition tag for the aut-sys object.
by Tony Bates 05 Feb '93

05 Feb '93

Please find enclosed a small propsed additional tag that I would like to get put into the next and perhaps final round of the documet due out early next. Also note that so far I have had little feedback on the paper as it stands. I have already made some changes in terms of cosmetics and some of the remaining holes but would still be interested in any comments. --Tony. Addition of a "default: " tag to the Proposed "aut-sys" database object. ------------------------------------------------------------------------ Currently, in the paper the method for detailing default routing is by use of the KEYWORD "DEFAULT" as I call it in the routing policy expression. However, upon reflection we feel it may be useful to to express this is terms of a tag itself. Basically, this details which AS neighbor you choose to select default routing to. So the format of the default tag would be. default: <as-num> <preference>, multiple lines, optional So for example if you are AS1 with two connections to the outside world, AS 2 and AS 4. And generally you take some transit networks in on both paths but select default for one (say AS 4) and if this goes away use AS 2 as backup this you would express it something like this. AS 3 | | --------------- AS 1------------AS 2-------------( Global ) | ( ) | ( Internet ) +------------AS 4-------------(_______________) | | | AS 5 The routing policy description would be as follows: aut-sys: AS1 as-in: AS2 100 AS2 AS3 as-out: AS2 AS1 as-in: AS4 100 AS4 AS5 as-out: AS4 AS1 default: AS4 100 default: AS2 150 <administrative stuff > If equal preferences are given this is also fine but of course the matter is purely local as to how this may be implemented. We also make distinction as to how default is reached (i.e. by a given network or use of 0.0.0.0, etc) as again this is purely a local bi-lateral matter and very much implementation dependent.

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Latest draft of routing policy paper.
by Tony Bates 03 Feb '93

03 Feb '93

Please find below the latest version of the routing paper. There are still some sections to be done. These are marked between chevrons ">>>"'s although there is not too much to be added.. We intend to release an updated and possibly the last draft early next week so please can I have all comments a.s.a.p. As an update there is already a proto-protoype parser that can parse the new proposed database formats and generate both gated and cisco access-lists (using NLC). We (Marten and I) intend to start a very small local pilot using these objects next week. --Tony. ------------------------------------------- Representation of IP Routing Policies in the RIPE Database Tony Bates Jean-Michel Jouanigot Daniel Karrenberg Peter Lothberg Marten Terpstra (Version 0.2) 1. Background RIPE is a collaborative body of European Regional IP network operators and service providers. European IP networking through its natural evolvement has grown into an extremely complex infrastructure and topology which in essence has even today no real single `co-ordinated core'. Conse- quently, there are many differing routing policies used within Europe. The RIPE Routing Working Group was formed to tackle many of the issues involved in large scale routing collaboration as is needed within Europe. To achieve the needed global connectivity the network operators and service providers need a way to easily and clearly express the vari- ous routing policies and provide a method for problem diag- nosis and trouble shooting when problems occur. A RIPE recommendation paper known as `ripe-60', titled "Pol- icy based routing within RIPE" was the outcome of a large amount of effort and discussion within the RIPE Routing Working Group. This tackled many of the issues relevant to the representation of IP routing polices and policy based routing within the RIPE community. It cites many of the per- tinent documents addressing the issues of policy based rout- ing and also proposes a method for representing routing pol- icy within the RIPE database. At the time of writing of `ripe-60' it was very unclear as to what direction the Euro- pean IP infrastructure and also routing implementations would take and was focused very much in terms of generality. It has become apparent that some of the problems with `ripe-60' is its generalised approach and perhaps somewhat abstract notation that in practice is not February 3, 1993 - 2 - easy for network operators to understand. Consequently, the authors of this document feel some clarification is needed and also some enhancement in terms of the current update in routing technology. A conscious effort has also been made to be somewhat less general. 2. Requirements This section describes the requirements of a scheme for representing routing information in the RIPE database. Clarity The representation must be easily explainable to network operators. If it is not, then it will not be used or worse will be used incorrectly. This also includes that it must either map well to the way network operators think about routing policy or provide them with a convenient way to start thinking about it. Translatability The representation must be translatable to and from router configuration files. The resulting configurations must be efficient in the sense that they are implementable with current router resources even in complex environments. If this requirement is not met there will be too many incon- sistencies between the published and the implemented poli- cies which will in turn cause hard to detect routing prob- lems. Checkability It must be possible to check the consistency of the pub- lished policies. Thus some level of redundancy is welcome if it adds value by making it possible to reveal inconsisten- cies. Applicability It must be possible to easily build diagnostic tools which help network operators to diagnose problems by making use of the policy information. These tools should answer questions like: "Which paths between network A and B are allowed by pub- lished policies ?" February 3, 1993 - 3 - "Which path will traffic between networks, network A and network B take when a certain routing path cannot be used for transit ?" "Does network A somehow have connectivity to all other net- work within RIPE ?" Generality The "Clarity" and "Translatability" requirements may push the design into the direction of large aggregations of net- works by routing and administrative domains. While this serves those requirements well the representation must make it possible to specify particular policies down to network granularity. Especially it should be possible to specify forwarding restrictions. <Hmm.... needs to be explained better I fear> 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 IP network number: Layer 3 entities. We do not mean organisations. We call the organisations operating networks "network opera- tors". For the sake of the examples we divide network operators into two categories: "service providers" and "cus- tomers". A "service provider" 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 ser- vice provider to universities and other academic organisa- tions, but in most cases it buys international connectivity from another service provider. A University networking department is a customer of the research networking organi- sation 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 Interior Routing Protocols (IGP). In most cases interior routing decisions are based on metrics derived from technical parameters like topology, link speeds and load (1). February 3, 1993 - 4 - ASes exchange routing information with other ASes using Exterior Routing Protocols (EGP). Exterior routing decisions are frequently based on policy based rules rather than purely on technical parameters. Until now there are no tools to configure complex policies and to communicate those policies between ASes while still ensuring proper operation of the Internet as a whole. Some EGPs like BGP-3/4 provide tools to filter routing information according to policy rules and more. None of them provides a mechanism to publish or communicate the policies themselves. Yet this is critical for operational coordination and fault isolation among net- work operators and thus for the operation of the global Internet as a whole. This paper proposes to use the RIPE database as a repository for publishing the policies of European ASes. There are two types of policy information which need to be represented in the database. These are "routing policies" and "access policies". Routing Policies The exchange of routing information between ASes is subject to routing 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 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 connection, ASX has to announce NET1 to ASY. 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. _________________________ (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. February 3, 1993 - 5 - 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 con- siders another way 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 accep- tance policies of ASX and ASY are identical. In order for traffic towards NET2 to flow announcement and acceptance 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 forwarding technology routing policies must eventually be expressed in these terms. It is relatively easy to formu- late reasonable policies in very general terms which CANNOT be expressed in terms of announcing and accepting networks. With current technology such policies are almost always impossible to implement. Usually separate policies are not configured for each net- work separately but for groups of networks. In practise these groups are almost always defined by the networks form- ing one or more ASes. By expressing routing policy in this way it should be noted that this information is only of use when you have full information for all networks within the global Internet. Equally, the current detail is only limited to the RIPE February 3, 1993 - 6 - database and for an AS exchanging routing reachability information for an AS whose information is not in the data- base we obviously cannot give a full representation of the ASes routing policy. Access Policies Access policies contrary to routing policies are not neces- sarily 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 unappropriate use of resources on network D has been made from network S and the problem has not been resolved yet. Other examples of access policies might be resources only accessible to networks belonging to a partic- ular 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 some- times hard to diagnose. Therefore they should also be docu- mented in the database according to similar requirements as outlined above.. 4. Proposed Database Objects Autonomous System (AS) An Autonomous System (AS) is a group of IP networks run by one or more network operators which has a single and clearly defined routing policy. In routing terms an AS will normally use an interior gateway protocol and some sort of common agreed metrics when exchanging network information within its own AS. An AS has a unique number associated with it which is used in both exchange of exterior routing information (i.e. net- work reachability information between ASes) and as an iden- tifier of the AS itself. Exterior routing protocols such as BGP are used to exchange routing information between ASes. The term AS is often confused or even misused as a con- venient 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. The creation of an AS should be done in a conscious and well February 3, 1993 - 7 - co-ordinated manner to avoid creating ASs for the sake of it, perhaps resulting in the worst case scenario of one AS per IP network number. It should be noted that there is a limited number of AS numbers available. This may mean that by applying the general rules for the creation and alloca- tion of as an AS below some re-engineering may 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 imple- mentations make use of a AS number as a form of tagging to identify the routing process. However, it should be noted that this key does not need to be unique unless exchanging routing information with other ASes. o An IP network number can and must only belong to one AS. This is a direct consequence of the fact that at each point in the Internet there can be exactly one routing policy for traffic destined to each network. In the case of the IP network which is used in neighbor peering between two ASs, say at the border between two ASs, a conscious decision must be made as to which AS this IP network number actually resides in. o For a simple case of customer networks connected to a single service provider, the IP network should be under the AS of the service provider. 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 information. This idea may at first seem slightly alien to many but it highlights a clear to distinction in the use of the AS number 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 different routing policies then they need to create their own AS. In the case of multi-homed customer net- works connected to two service providers say for exam- ple where a network operator is initially connected to a single service provider and then decides for whatever reason to connect to another service provider there are now at least two different routing policies 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 February 3, 1993 - 8 - representation of policy and preference to the dif- ferent service providers. This is the only case where a network operator should create it own AS number. o When creating an AS you should always try to populate the AS with as many IP networks as possible providing all IP networks conform to the same routing policy. With the above rules in mind it means that if for example, when a network operator changes service provider it will move from one AS to another. Once the database is being used as hoped for routing then a clear procedure is needed for making sure this AS transition takes place in a smooth and transparent manner without any loss of connectivity. See Appendix C for detail of how this should be done. Each AS is represented in the RIPE database by both an AS object and AS tags on the network objects representing the networks belonging to the AS. The AS objet stores descrip- tive, administrative and contact information about the AS as well as the routing policies of the AS in relation to all neighboring ASes. The AS tags on the network objects define the set of net- works belonging to an AS. Each network can have exactly one AS tag. The AS tags can only be created and updated by the "guardian" of the AS and not by those immediately responsi- ble for the particular network. This ensures that operators, especially service providers, remain in control of AS membership. The example below shows how this would be represented in terms of the network object. The tag "aut- sys" is used. Refer to `ripe-50' for a complete description of the network object in the RIPE database. Example: 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 aut-sys: AS1104 rev-srv: ns.ripe.net changed: marten(a)ripe.net 930121 source: RIPE February 3, 1993 - 9 - The AS object itself is used to represent a description of administrative details and the routing policies of the AS itself. The AS object definition will be depicted as fol- lows. Example: aut-sys: AS1104 descr: NIKHEF-H Autonomous system as-in: AS1213 100 AS1213 as-in: AS1913 100 AS1913 as-in: AS1755 150 ANY as-out: AS1213 ANY as-out: AS1913 ANY as-out: AS1755 AS1104 AS1913 AS1213 tech-c: Rob Blokzijl admin-c: Eric Wassenaar guardian: as-guardian(a)nikhef.nl source: RIPE changed: k13(a)nikhef.nl 920713 changed: ripe-dbm(a)ripe.net 920910 See Appendix A for a complete definition of the "aut-sys" syntax. It should be noted that this representation provides two things: - a set of networks - a description of administrivia and routing policies The set of networks can be used to generate network list based configuration information as well as configuration information for EGPs 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! Community A community is a group of networks that cannot be represented by an AS or a group of AS numbers. It is in some circumstances useful to define a group of networks that have something in common. This could be a special access policy to a supercomputer centre, a group of networks used for a specific mission, or a disciplinary group that is scattered among several autonomous systems. Also these com- munities could be useful to group networks for the purpose February 3, 1993 - 10 - of network statistics. Communities do not exchange routing information directly, since they do not represent a autonomous system. More specifically, communities do not define routing policies, but access or usage policies. Contrary to an AS, networks can belong to more than commun- ity. Communities should be defined in a strict manner, to avoid creating as many communities as there are networks, or even worse. Communities should be define following the following three rules: o Communities must have a global meaning. Communities must have a meaning beyond the local environment Com- munities that have no global meaning, and are used only in a local environment must be avoided. o Communities must not be defined to express non-local polices. 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 organisa- tion. Community examples There are some clear examples of communities: PROVIDER - all customers of a given service provider even though they can have various different routing polices and hence belong to different ASes. This would extremely useful for statistics collection. HEPnet - the High Energy Physics Network currently shares infrastructure with other organisations, and the insti- tutes it consists of are scattered all over Europe, often being part of a non HEPnet autonomous system. To allow statistics or access policies, a community HEP- net, consisting of all networks that are part of HEP- net, nicely groups all these networks. NSFNET - the National Science Foundation Networks imposes an February 3, 1993 - 11 - acceptable use policy on networks that wish to make use of it. A community NSFNET could imply the set of net- works that comply to this policy. 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 ser- vice 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 to for instance to do topology or bandwidth planning. Each community is represented in the RIPE database by both a community object and community tags on the network objects representing the networks belonging to the community. The community objet stores descriptive, administrative and con- tact information about the community. The community tags on the network objects define the set of networks belonging to a community. Each network can have multiple one 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 particular net- work. This ensures that communities 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. Here we have an example where the network 192.16.199.0 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 network. Nikhef-H uses the service provider SURF- net (a service provider containing customers with more than one routing policy), is also part of the High Energy Physics community as well as having the ability to access the Cray at CERN (2). _________________________ (2) The community `CERN-CRAYUSERS' is somewhat notional but is intended as an example of a possible use of an access policy constraint. February 3, 1993 - 12 - Example: inetnum: 192.16.199.0 netname: HEFNET descr: Local Ethernet descr: NIKHEF section H descr: Science Park Watergraafsmeer descr: Amsterdam descr: The Netherlands country: NL admin-c: Eric Wassenaar tech-c: Rob Blokzijl aut-sys: 1104 comm-list: HEPNET CERN-CRAYUSERS SURFNET nsf-in: 1=590 gateway: nih changed: ripe-dbm(a)ripe.net 920604 source: RIPE In the above examples some communities have been defined. The community object itself will take the following format: Example: community: JANET descr: UK Joint Academic Network authority: The Joint Network Team guardian: comm-guardian(a)jnt.ac.uk admin-c: James Hutton tech-c: Bob Day changed:ripe-dbm@ripe.net 920604 source: RIPE For a complete explanation of the syntax please refer to Appendix B. 5. Representation of Routing Policies Routing policies of an AS are represented in the autonomous system object. Initially we show some examples without the full syntax in place so the reader is familiar with the con- cept of how routing information is represented, used and derived. Refer to section X for the full syntax of the "as" object. The topology of routing exchanges is represented by listing February 3, 1993 - 13 - how routing information is exchanged with each neighboring AS. This is done separately for both incoming and outgoing routing information. In order to provide backup and back door paths a priority is associated with incoming informa- tion. Example 1: AS1------AS2 as: AS1 <administrivia go here> as-out: AS2 = AS1 # announce all networks in AS1 to AS2 as-in: AS2 = 100 AS2 # accept all AS2 networks from AS2 as: AS2 <administrivia go here> as-out: AS1 = AS2 # announce all networks in AS2 to AS1 as-in: AS1 = 100 AS1 # accept all AS1 networks from AS1 This specifies a simple routing exchange of two presumably isolated ASes. Even if either of them has routing informa- tion about networks in ASes other than AS1 and AS2, none of that will be announced to the other. The number 100 in the inbound specifications is a relative priority. 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 higher priority. This is consciously simi- lar to 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 February 3, 1993 - 14 - 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 database will remain unchanged as will be the part of AS2's representation describing the routing exchange with AS1. A description of the additional routing exchange with AS3 will be added to AS2's representation: as: AS1 <administrivia go here> as-out: AS2 = AS1 # announce all networks in AS1 to AS2 as-in: AS2 = 100 AS2 # accept all AS2 networks from AS2 as: AS2 <administrivia go here> as-out: AS1 = AS2 # announce only networks in AS2 to AS1 as-in: AS1 = 100 AS1 # accept all AS1 networks from AS1 as-out: AS3 = AS2 # announce only networks in AS2 to AS3 as-in: AS3 = 100 AS3 # accept all AS3 networks from AS3 as: AS3 <administrivia go here> as-out: AS2 = AS3 # announce all networks in AS3 to AS2 as-in: AS2 = 100 AS2 # accept all AS2 networks from AS2 Note that in this example AS2 keeps full control over its resources. Even if AS3 and AS1 were to allow each other's routes in from AS2, the routing information would not flow because AS2 is not announcing it. (*) Example 2b: If contrary to the previous case, AS1 and AS3 are supposed to have connectivity to each other via AS2, all AS objects _________________________ (*) of course AS1 and AS3 could just send traffic to each other to AS2 even without AS2 announcing the net- works, hoping that AS2 will forward it correctly. Such questionable practises however are beyond the scope of this document. February 3, 1993 - 15 - have to change: as: AS1 <administrivia go here> as-out: AS2 = AS1 # announce all networks in AS1 to AS2 as-in: AS2 = 100 AS2 AS3 # accept AS2 and AS3 networks from AS2 as: AS2 <administrivia go here> as-out: AS1 = AS2 AS3 # announce all networks in AS2 and AS3 to AS1 as-in: AS1 = 100 AS1 # accept all AS1 networks from AS1 as-out: AS3 = AS2 AS1 as-in: AS3 = 100 AS3 as: AS3 <administrivia go here> as-out: AS2 = AS3 # announce all networks in AS3 to AS2 as-in: AS2 = 100 AS1 AS2 # accept AS2 and AS1 networks from AS2 Note that the amount of routing information exchanged with a neighbor AS is defined in terms of networks belonging to ASes. In BGP terms this is the AS where the routing infor- mation originates and the originating AS information carried in BGP could be used to implement the desired policy. How- ever using BGP or the BGP AS-path information is not required to implement the policies thus specified. Confi- gurations based on network lists can easily be generated from the database. The BGP derived information can then be used as an additional checking tool as desired. The specifications know some special sets and can be expressed as boolean expressions: ANY - means any routing information known. For output this means that all networks an AS knows about are announced. For input it means that anything is accepted from the neighbor AS. DEFAULT - <explanation of DEFAULT goes here, tell us what's dif- ferent from ANY!> February 3, 1993 - 16 - Example 3: AS4 is a stub customer AS which only talks to service pro- vider AS123. | | -----AS123------AS4 | | as: AS4 # representation of AS4 in the database <administrivia> as-out: AS123 = AS4 # announce only networks in AS4 to AS123 as-in: AS123 = 100 ANY # accept any announcement from AS123 as: AS123 # representation of the service provider AS123 <administrivia> as-in: AS4 = 100 AS4 # accept routes for customer AS4's networks as-out: AS4 = ANY # provide all routes to customer AS4 <further neighbors> Example 4: AS4 now connects to a different operator, AS5. AS5 uses AS123 for outside connectivity but has itself no direct con- nection 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 | | February 3, 1993 - 17 - as: AS4 # representation of AS4 in the database <administrivia> as-out: AS123 = AS4 AS5 # own and AS5 networks to AS123 as-in: AS123 = 100 ANY # accept any announcement from AS123 as-out: AS5 = ANY # send all announcements through to AS5 as-in: AS5 = 50 AS5 # accept only AS5 announcements from them as: AS5 <administrivia> as-out: AS4 = AS5 as-in: AS4 = 100 ANY as: AS123 # representation of the service provider AS123 <administrivia> as-in: AS4 = 100 AS4 AS5 # accept AS4's own and AS5 from AS4 as-out: AS4 = ANY # all to customer AS4 and via it to AS5 <further neighbors> Now AS4 has two sources of external routing information. AS5 which provides only information about its own networks and AS123 which provides information about the external world. Note that accepts information about AS5 from both AS123 and AS5 although AS5 information cannot come from AS123 since AS5 is connected only via AS4 itself. The higher priority 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. 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; February 3, 1993 - 18 - 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 des- tined 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 destinations 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. Example 5a: as: AS4 as-in: AS123 = 100 NOT AS6 # accept anything besides AS6 as-out: AS123 = AS4 # announce only ourselves to AS123 as-in: AS6 = 50 AS6 # accept AS6 only from AS6 as-out: AS6 = AS4 # announce only own nets to AS6 as: AS123 as-in: AS4 = 100 AS4 as-out: AS4 = ANY as-in: AS6 = 100 AS6 as-out: AS6 = ANY <further neighbors> as: AS6 as-in: AS123 = 100 NOT AS4 as-out: AS123 = AS6 as-in: AS4 = 50 AS4 as-out: AS4 = AS6 February 3, 1993 - 19 - 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 check- ing tools might flag these cases however. Example 5b: as: AS4 as-in: AS123 = 100 ANY # expect anything from AS123 as-out: AS123 = AS4 # announce only ourselves to AS123 as-in: AS6 = 50 AS6 # accept AS6 only from AS6 as-out: AS6 = AS4 # announce only own nets to AS6 as: AS123 as-in: AS4 = 100 AS4 as-out: AS4 = ANY as-in: AS6 = 100 AS6 as-out: AS6 = ANY <further neighbors> as: AS6 as-in: AS123 = 100 ANY as-out: AS123 = AS6 as-in: AS4 = 50 AS4 as-out: AS4 = 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 announce- ment from AS6 will be preferred because of its better (numerically lower) preference and thus the private link will be used as desired. AS6 is configured as a mirror image. 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. February 3, 1993 - 20 - as: AS4 as-in: AS123 = 100 ANY # expect anything from AS123 as-out: AS123 = AS4 # announce only ourselves to AS123 as-in: AS6 = 50 AS6 # accept AS6 only from AS6 as-in: AS6 = 110 ANY # accept anything from AS6 (worse than AS123) as-out: AS6 = AS4 # announce only own nets to AS6 as: AS123 as-in: AS4 = 1 AS4 as-out: AS4 = ANY as-in: AS6 = 1 AS6 as-in: AS6 = 2 AS4 # now also accept AS4 from AS6 in case backup as-out: AS6 = ANY <further neighbors> as: AS6 as-in: AS123 = 100 ANY as-out: AS123 = AS6 AS4 # for backup also pass AS4 to AS123 as-in: AS4 = 50 AS4 as-out: AS4 = ANY # for backup export all we know to AS4 Note that it is important to make sure to propagate routing information for both directions in backup situations like this. Connectivity 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. 6. RIPE Database Update Procedure This section describes a procedure for updating the routing attributes in the RIPE database as mentioned in this sec- tion. These routing tags are essential for the routing of networks that are known in the RIPE database. Therefore updates of these attributes must be: - Properly authorised - Guarded against typing errors - Efficient for both maintainers of the attributes and the maintainers of the whole database February 3, 1993 - 21 - The procedure For each of the AS and Community tags, a list of all net- works having this attribute is kept separately from the gen- eral database itself. These lists will be the *only* source of routing information used in the database. Normal data- base updates *never* change these attributes. If an update includes such an attribute and a discrepancy between the values in the update and those in the database is found, a diagnostic message will be sent to the originator of the update. The attributes as defined in the files are incor- porated in the database at each normal update run. To ensure proper control and authorisation, we propose to main- tain the lists on a the central NCC database server, where each of the guardians of a tag keeps track of his or her own list. The lists are maintained through individual logins for each of the guardians. The guardians can themselves decide in what manner they want to update their list. The NCC will offer interactive logins, ftp logins or any other means that might be deemed useful. File Format We propose to keep the file format as simple as possible. The name of the file should indicate the name of the attri- butes. This means that there cannot be two attributes with the same name. The format within the file we propose as the "inetnum:" entry for each of the networks, separated by an empty line. If a guardian feels that he would want more fields to identify a network that will get his attribute, he is free to do so. An attribute will only be added to a net- work if all fields defined in the list match a network in the database. Advantages The update procedure as proposed above has the following advantages: - Authorisation of adding/deleting is guaranteed. - No need for mailing back and forth of authorisation messages. - Simple procedure for both database maintainers and guardians. - Guardians keep full control of their attribute. - Could be implemented at the NCC without too much delay. February 3, 1993 - 22 - 7. Summary In summary this paper basically introduces two new RIPE database objects, the autonomous system -- "aut-sys" and the community -- "community" object. It attempts to clarify terms in such a way as to make them easier and more usable for network operators. It provides a mechanism to easily and clearly express routing policy and provide a mechanism to create, maintain and administer network based filter lists for routing policy. It introduces the concept of autonomous systems and provides the tools for routing protocols that can make use of AS information. >> >> Still needs more summary text >> 8. Glossary It is felt useful to include a basic glossary of some of the terms used within this paper to act as both a reference and as possible clarification tool. >> >> To be done >> 9. Author's Addresses Tony Bates RIPE Network Coordination Centre Kruislaan 409 NL-109SJ Amsterdam +31 20 592 5065 Tony.Bates(a)ripe.net Daniel Karrenberg RIPE Network Coordination Centre Kruislaan 409 NL-109SJ Amsterdam +31 20 592 5065 D.Karrenberg(a)ripe.net Jean-Michel Jouanigot CERN, European Laboratory for Particle Physics CN division CH-1211 Geneva 23 Switzerland + 41 22 767 4417 jimi(a)dxcoms.cern.ch Peter Lothberg STUPI February 3, 1993 - 23 - Box 9129 102 72 Stockholm +46 8 6699720 roll(a)stupi.se Marten Terpstra RIPE Network Coordination Centre Kruislaan 409 NL-109SJ Amsterdam +31 20 592 5065 M.Terpstra(a)ripe.net February 3, 1993 - 24 - Appendix A -- Syntax for the "aut-num" object. Here is a summary of the tags associated with aut-num object itself: aut-num: [mandatory] descr: [mandatory] [multiple] as-in: [optional] [multiple] as-out: [optional] [multiple] tech-c: [mandatory] [multiple] admin-c: [mandatory] [multiple] guardian: [mandatory] remarks: [optional] [multiple] changed: [mandatory] [multiple] source: [mandatory] [RIPE] Each item has the following syntax: aut-num: Autonomous system number. This must be a uniquely allocated autonomous system number from a AS registry (i.e. the RIPE NCC or the Inter NIC). Format: AS<positive integer between 1 and 65336> Example: aut-num: AS1104 Status: mandatory descr: A short description of the Autonomous system. Format: free text, one line per entry, multiple lines in sequence Example: descr: NIKHEF section H descr: Science Park Watergraafsmeer descr: Amsterdam Stautus: mandatory as-in: A description of accepted routing information between other AS peers. Format: <aut-num> <preference> <routing policy expression>, on multiple lines. <aut-num> refers to your AS neighbor. <preference> is a positive integer used to express a relative preference of routes learned. The lower the preference the more February 3, 1993 - 25 - preferred the route. <routing policy expression> can take the following formats. 1. A list of of one or more ASes. Example: as-in: AS1103 100 AS1103 as-in: AS786 105 AS1103 as-in: AS786 10 AS786 as-in: AS1755 110 AS1103 AS786 2. A set of KEYWORDS. The following keywords are currently defined. ANY - this means anything the neighbor AS knows. DEFAULT - a common agreed default network. RIPE-DB - any network currently in the RIPE database. LOCAL - any network in the RIPE database which is part of the community LOCAL (i.e. no connectivity outside it own organisation). 3. A logical expression of the above of either 1 or 2 above The current logical operators are defined as: AND OR NOT Rules are grouped togethered using parenthesis i.e "(" or ")". Example: as-in: AS1755 100 RIPE-DB AND NOT (LOCAL AS1234 AS513) as-in: AS1755 150 DEFAULT Stautus: optional as-out: A description of generated routing information sent to other AS peers. Format: <aut-num> <routing policy expression>, multiple lines. <aut-num> refers to your AS neighbor. <routing policy expression> is explained in the as-in definition above. Example: as-out: AS1104 AS978 as-out: AS1755 ANY as-out: AS786 RIPE-DB AND NOT (AS978 LOCAL) tech-c: Name of technical contact person. February 3, 1993 - 26 - This is someone to be contacted for technical problems such as misconfiguration, technical problems. Format: <firstname> <initials> <lastname>, multiple lines. Example: tech-c: John E. Doe Status: mandatory admin-c: Name of administrative contact person. This probably be the name of the guardian but may not be. Format: <firstname> <initials> <lastname>, multiple lines. Example: admin-c: Joe T. Bloggs Status: mandatory guardian: Malibox of the guardian of the Autonomous system. Format: <email-address>, single line. Example: guardian: as1104-guardian(a)nikhef.nl Status: mandatory source: RIPE Source of the information. This is used to separate information from different sources kept by the same database software. Format: RIPE Status: mandatory changed: Who and when changed this last. Format: <email-address> YYMMDD Example: changed: johndoe(a)terabit-labs.nn 900401 Status: mandatory remark: Remarks/comments Format: text string, multiple lines Example: February 3, 1993 - 27 - remark: Multihomed AS talking to AS 1755 and AS786 remark: Will soon connect to AS 1104 also. Status: optional February 3, 1993 - 28 - Appendix B -- Syntax details for the "community" object. Here is a summary of the tags associated with "community" object itself: community: [mandatory] descr: [mandatory] [multiple] authority: [mandatory] guardian: [mandatory] tech-c: [mandatory] [multiple] admin-c: [mandatory] [multiple] remarks: [optional] [multiple] changed: [mandatory] [multiple] source: [mandatory] [RIPE] Each item has the following syntax: community: Name of community. Should be as representative of the cummunity as possible rather than being something obscure. Format: Text string which cannot start with "AS-" or any of the <routing policy expression> KEYWORDS. See Appendix A. Example: community: WCW descr: A short description of the community represented. Format: free text, one line per entry, multiple lines in sequence Example: descr: Science Park Watergraafsmeer descr: Amsterdam Stautus: mandatory authority: The formal authority for this community. This could be an organisation, institute, etc. Format: text Example: authority: WCW LAN committee Stautus: mandatory guardian: February 3, 1993 - 29 - Malibox of the guardian of the community. Format: <email-address>, single line. Example: guardian: wcw-guardian(a)nikhef.nl Status: mandatory tech-c: Name of technical contact person. This is someone to be contacted for technical problems such as misconfiguration, technical problems. Format: <firstname> <initials> <lastname>, multiple lines. Example: tech-c: John E. Doe Status: mandatory admin-c: Name of administrative contact person. This probably be the name of the guardian but may not be. Format: <firstname> <initials> <lastname>, multiple lines. Example: admin-c: Joe T. Bloggs Status: mandatory source: RIPE Source of the information. This is used to separate information from different sources kept by the same database software. Format: RIPE Status: mandatory changed: Who and when changed this last. Format: <email-address> YYMMDD Example: changed: johndoe(a)terabit-labs.nn 900401 Status: mandatory remark: Remarks/comments Format: text string, multiple lines Example: February 3, 1993 - 30 - remark: This a group of institutes at WCW. remark: Consisting of CWI, SARA and NIKHEF. Status: optional February 3, 1993 - 31 - Appendix C -- Some additional thoughts. This section is essentially marked as "for further study". However, the details are felt relevant enough to be covered in an appendix for those who are interested. AS Macros For an AS that doesn't use default routing it may be diffi- cult for it to keep track of each and every new AS that is represented in the database. A convenient way around this create an `AS Macro' which essentially is a convenient way to groups or aggregate ASes. This would be done so that each and every AS guardian does not have to add an new AS to it's as-in or as-out tags for it's AS object. However, it should be noted that creates an implicit trust on the guardian of the AS-Macro. The proposed idea would be to allow an AS-Macro as part of the <routing policy expression> for the "as-in" and "as-out" tags. The object could then be used as a list or group of ASes. So for example we could create an AS object as fol- lows: Example: aut-sys: AS786 as-in: AS1755 100 AS-EBONE AND NOT AS1104 as-out AS1755 AS786 The proposed syntax for an AS macro would be as follows: as-macro: [mandatory] descr: [mandatory] as-list: [mandatory] [multiple] guardian: [mandatory] tech-c: [mandatory] [multiple] admin-c: [mandatory] [multiple] remarks: [optional] [multiple] changed: [mandatory] [multiple] source: [mandatory] [RIPE] >>> >>> Actual details still to be completed >>> February 3, 1993 - 32 - Transitioning from one AS to another. >>> >>> To be done >>> February 3, 1993

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resource object proposal
by Milan Sterba 16 Jan '93

16 Jan '93

As we decided at the last RIPE meeting, I republish the proposal of a resource object to be added to the RIPE DB structure and optionally implemented by national registries. I made almost no modifications to my previous proposal (just added audio and videocasting channel). I hope this publication will sollicitate some preliminary discussion on e-mail before the upcomming RIPE meeting. Thanks for comments and see you in Prague Milan Sterba Description of the "resource" RIPE database object ================================================== resname: Resource name in human Mandatory admin-c: Name of administrative contact person Format : <firstname> <initials> <lastname> Mandatory tech-c: Name of the technical contact person Format : <firstname> <initials> <lastname> Mandatory restype: Type of the resource Describes in one word the nature of the resource (the list of the most common should be agreed upon at RIPE) Format : one of the strings listed bellow meta = server of servers library = library catalogue docs = document store database = structured data base local = local information system (e.g. university information system) archive = specific data objects archive (e.g. public domain software) super = supercomputer facility channel = audio or videocasting station Mandatory acc-method: Access protocol to the service This should be the name of the IP [CLNP] service which allows to access the server Format: sequence of bellow listed strings separated by space telnet | ftp | ftam | wais | gopher | www | e-mail | prospero | archie | vat ... Mandatory acc-key: Access info necessary to access the first level service (e.g. login name for public telnet sessions or port number and database name for wais servers) Format: depends on the access protocol acc-right: Access rights to the resource Format : sequence of strings bellow separated by space ANY | see connect attribute in network object | LIMITED Mandatory topics: Keyword description of the topics covered by the resource Each topic should be mentioned in a new topic attribute. e.g. economy, mollecular biology, computer networks, software Mandatory description: Short description of the resource Postal address is not needed, it can be found via the contacts host: List of hosts for this resource Format: fully qualified domainname without trailing "." Mandatory media: Type of data stored on the server Format: sequence of strings bellow separated by space ascii = ascii texts text = other textual data (e.g. in native language or various text processing formats - PostScript) struct = record oriented data graphics = graphical data (images) sound = self explanatory video = dtto binaries = computer programs in binary form sources = computer program sources etc. -- ====================================================================== Prague School of Economics e-mail : Milan.Sterba(a)vse.cs Computing Center tel : +42 2 21 25 704 nam. W. Churchilla 4 home: +42 2 823 78 59 130 67 Praha 3 fax : +42 2 235 85 09 Czechoslovakia =======================================================================

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RIPE Database Update Scripts
by Daniel Karrenberg 13 Jan '93

13 Jan '93

Some of the database updates scripts we released on Friday neglect to check for the presence of the configuration file. This can cause hard to diagnose errors. The checks have been added and a new version released at the same place as before: ftp.ripe.net:~ftp/tools/db-scripts.shar.Z Thanks to Daniele Vannozzi of the GARR NIS for reporting the bug. Daniel

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Database Software
by Daniel Karrenberg 08 Jan '93

08 Jan '93

We still need to make a new version of the database indexing and whois-server software which will be controllable by configuration file. The NCC have been thinking about the design of these modules and we came to the conclusion that a total rework is worthwhile. Once we do a total rework we can of course incorporate new features. Some of the features we were thinking about are - (almost) fully controllable via config file - dynamic updates (as opposed to batch updates) This would mean changes are immediately visible in whois - simple update protocol for local registries This would mean that registries could do dynamic and immediately visible updates directly and not via mail - exchange facilities with global internet registry We are currently implementing some prototypes in the PERL language which provides excellent portability. Actually the RIPE database is now running on my laptop PC ;-). We are contemplating of using PERL for the production version as well. If you have any input about this, please let us know. We are especially interested in features required for the local registries. Regards Daniel

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RIPE Dasatase
by Daniel Karrenberg 08 Jan '93

08 Jan '93

The revised database update scripts are now available on ftp.ripe.net as file ~ftp/tools/db-scripts.shar.Z. These are the scripts we use to process database entries. A subset of them can be used to check database entries for correct syntax etc. A big thanks to the beta testers for trying them first. If yoy have problems using the scripts, please let us know. Daniel

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RIPE Whois Server Software Available
by Daniel Karrenberg 08 Jan '93

08 Jan '93

The RIPE whois server software is now available from ftp.ripe.net as file ~ftp/tools/whois-server.shar.Z. This is just the software which allows you to query a RIPE database file. The updates scripts will be released separately. If you have trouble installing the package, please let me know. If you use the package to run a full-service RIPE database server, please notify ncc(a)ripe.net. If apporpriate we can then arrange to automatically re-direct queries from your area to that server. We also ask every full-service RIPE database server to enable query logging and send us the results regularly because we would like to publish usage statistics of the RIPE database as such in the NCC quarterly reports. Daniel

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None
by Peter Lothberg 27 Nov '92

27 Nov '92

> daniel, > > i feel that it is EBSes task to protect themself from poluted or > nonregistered routes. RBSs should be considered non safe boxes by > EBONE. that is at least our commercial IP backbone is run. > > -- juha > Right. The problem we are having right now, is that some EBS sites protect themself from other EBS sites. And you can understand what hapens in the non syncronized IBGP way the Ebone is set up...... -Peter

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None
by Daniel Karrenberg 27 Nov '92

27 Nov '92

> Juha Heinanen <Juha.Heinanen(a)datanet.tele.fi> writes: > daniel, > > i feel that it is EBSes task to protect themself from poluted or > nonregistered routes. RBSs should be considered non safe boxes by > EBONE. that is at least our commercial IP backbone is run. Actually I strongly feel the same way. I simply didn't consider it appropriate for the NCC to set EBONE policy. That's why I left it open. Daniel

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(no subject)
by Daniel Karrenberg 27 Nov '92

27 Nov '92

Friends, I have the distinct impression that we are lagging in our efforts to make effective use of the RIPE database for EBONE routing. The current state of affairs is - The framework is described in: ripe-60, "Policy based routing within RIPE", May 1992 - The database software has been extended to handle the objects described in ripe-60 - CERN and some others have started to use them internally makeing use of the CERN developed "nlc" tool - A draft paper on how to apply ripe-60 to EBONE routing has been circulated lately: "Use of the "RIPE policy based Routing within EBONE" by Jean-Michel Jouanigot, September 1992 What needs to be done is to agree on how the route filtering functions necessary for EBONE operations are going to be done. At the NCC we have wondered a little why there seems to be little progress if any. It seems to be that everyone is waiting until someone else reports first experiences how to use the new database objects and tells the others how to use this. Also there seems to be widespread fear about unnecessary complexity. As a consequence little progress is made. In the light of this we have decided to propose a simple first step to get two things going: - ability to filter outgoing announcements RBS->EBS with the goal of keeping EBONE routes unpolluted - update procedures for routing attributes in RIPE database The proposal below deals with those two things. Additional functionality can be added later once these two basic things work. In order to move this forward the EOT should talk about this and make constructive comments where necessary. If there is rough consensus to proceed in this way, then the NCC and the EBONE operations people can work together to get this operational within a few weeks. Please excuse the late date of sending this over. We are currently very pressed for time at the NCC and the real extent of the problem became apparent only recently. We are also unfortunately unable to attend the Montpellier meetings. E{A,O}T can be assured that we will make all reasonable efforts to make the RIPE database useful for EBONE routing purposes. Daniel First Steps to Use the RIPE Database for Policy Based Routing within EBONE -------------------------------------------------------------------------- By far the easiest way to start implementing route filtering as specified in the RIPE document ripe-60 is by using the routing privilege tag. In order to achieve this each of the connected regions of EBONE has to define routing privileges, one routing privilege for each of the different policies inside the region. Of course ideally there would be only one such policy but the world is seldom ideal. Once the routing privileges have been defined they need to be registered in the RIPE database using the routing privilege object. Having defined and registered the necessary routing privileges, the region must then make sure that all the network numbers that need to be announced to EBONE get the appropriate routing privilege tag added to the routpr-list attribute in the database. With the Network List Compiler (nlc) filter lists containing all the networks that have a certain set of routing privileges are then created. These can then be applied on the EBS side, to filter incoming routing updates from the RBS, or on the RBS side to filter outgoing updates to the EBS. The NCC offers to produce such list for any RBS operator requesting it. Of course nlc can also be run locally using local copies of the RIPE database. This model however does not specify backup policies, it just specifies primary routing. If a certain region provides a backup connection to EBONE for another region, this first region must tell the EBONE operators to accept both the list of networks with his own routing privileges, and the list of the backed-up region. AS path lengths or weights should be used to ensure that the best routes are chosen first. A method of storing this information in the RIPE database will be introduced at a later stage. Using the routing privilege in this fashion is similar to using for instance the autonomous system tag in the database for the same purpose. However, the routing privilege allows more detail inside an autonomous system. One should expect that every policy inside a region should have its own AS number, but unfortunately this is not the case in many places. Therefore, the use of the routing privilege gives the needed granularity in defining policies. This model also can easily be extended to the Global Internet Exchange by creating a filter list for the superset of all routing privileges that are announced to EBONE. Database Update Procedures for the Routing Tags ----------------------------------------------- Note These preocedures have been presented to the RIPE database working group a few weeks ago and all comments received have been incorporated. Introduction This describes a procedure for updating the routing attributes to the RIPE database as defined in ripe-60. These routing tags are essential for routing of networks that are known in the RIPE database. Therefore updates of these attributes must be: - properly authorized - guarded against typing errors - efficient for both maintainers of the attributes and the maintainers of the whole database The Principle The principle of the procedure is that the information concerning the routing related attributes is maintained separately from the database proper. Update procedures for the database itself do not change the routing related information. The routing information can only be changed by the "guardians" of specific routing privilegesd and boundary gateways. When information is retrieved from the database however the routing related information presented together with the other information. The Procedure For each of the routing privileges and boundary gateways tags, a list of all networks having this attribute is kept seperately from the database proper. These lists will be the *only* source of routing information used in the database. Normal database updates do *never* change the routing related attributes. If an update include such an attribute it causes a consistency check with the stored information but no update occurs. If a discrepancy between the values in the update request and those in the database is found, a diagnostic will be send to the originator of the request. The routing related attributes as defined in the lists are merged into the database at each normal update run. To ensure authorisation, we propose to maintain the lists on a the central NCC database server, where each of the guardians of a tag keeps track of his or her own list. The lists are maintained through individual logins for each of the guardians. The guardians can themselves decide in what manner they want to update their list. The NCC will offer interactive logins, ftp logins or any other means that might be found useful. File Format We propose to keep the file format as simple as possible. The name of the file should indicate the name of the attributes. This means that there cannot be two attributes with the same name. The format within the file we propose as the "inetnum:" entry for each of the networks, seperated by an empty line. If a guardian feels that he would want more attributes to identify a network for reasons of consistency checking, he is free to do so. A routing related attribute will only be added to a network if all attributes defined in the list match a network in the database. Advantages The update procedure as proposed above has the following advantages: - Authorisation of adding/deleting is guarenteed - No need for mailing back and forth of authorisation messages - Simple procedure for both database maintainers and guardians - Guardian keeps full control of his attribute - Could be implemented at the NCC without too much delay

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