RFC 2519 (rfc2519) - Page 2 of 13

A Framework for Inter-Domain Route Aggregation

RFC 2519             Inter-Domain Route Aggregation        February 1999


        This policy work is the cornerstone which makes efficient route
        aggregation technically possible.

      - Route aggregation by large (especially "Tier 1") providers.  To
        date, the largest reductions in the size of the routing table
        have resulted from efficient aggregation by large providers.

   However, the ability of various levels of the global routing system
   to implement efficient aggregation schemes varies widely.  As a
   result, the size and growth rate of the Internet routing table, as
   well as the associated route computation required, remain major
   issues today.  To support Internet growth, it is important to
   maximize the efficiency of aggregation at all levels in the routing
   system.

   Because of the current size of the routing system and its dynamic
   nature, the first step towards this goal is to establish a clearly
   defined framework in which scaleable inter-domain route aggregation
   can be realized.  The framework described in this document is based
   on the predominant and current experience in the Internet. It
   emphasizes the philosophy of aggregation by the source, both within
   routing domains as well as towards upstream providers.  The framework
   also strongly encourages the use of the "no-export" BGP community to
   balance the providersubscriber need for more granular routing
   information with the Internet's need for scalable inter-domain
   routing.  The advantages of this framework include the following:

      - Route aggregation is done in a distributed fashion, with
        emphasis on aggregation by the party or parties injecting the
        aggregatable routing information into the global mesh.

      - The flexibility of a routing domain to be able to inject more
        granular routing information to an adjacent domain to control
        the resulting traffic patterns, without having an impact on the
        global routing system.

        In addition to describing the philosophy, we illustrate it by
        presenting sample configurations.  IPv4 prefixes, BGP4 and ASs
        are used in examples, though the principles are applicable to
        inter-domain route aggregation in general.

        Address allocation policies and technologies to renumber entire
        networks, while very relevant to the realization of successful
        and sustained inter-domain routing, are not the focus of this
        document.  The references section contains pointers to relevant
        documents [8, 9, 11, 12].





Chen & Stewart               Informational