Autonomous confederations
RFC 975

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Network Working Group                                        D. L. Mills
Request for Comments: 975                               M/A-COM Linkabit
                                                           February 1986

                       Autonomous Confederations

Status of This Memo

   This RFC proposes certain enhancements of the Exterior Gateway
   Protocol (EGP) to support a simple, multiple-level routing capability
   while preserving the robustness features of the current EGP model.
   It requests discussion and suggestions for improvements.
   Distribution of this memo is unlimited.

Overview

   The enhancements, which do not require retrofits in existing
   implementations in order to interoperate with enhanced
   implementations, in effect generalize the concept of core system to
   include multiple communities of autonomous systems, called autonomous
   confederations. Autonomous confederations maintain a higher degree of
   mutual trust than that assumed between autonomous systems in general,
   including reasonable protection against routing loops between the
   member systems, but allow the routing restrictions of the current EGP
   model to be relaxed.

   The enhancements involve the "hop count" or distance field of the EGP
   Update message, the interpretation of which is not covered by the
   current EGP model.  This field is given a special interpretation
   within each autonomous confederation to support up to three levels of
   routing, one within the autonomous system, a second within the
   autonomous confederation and an optional third within the universe of
   confederations.

1.  Introduction and Background

   The historical development of Internet exterior-gateway routing
   algorithms began with a rather rigid and restricted topological model
   which emphasized robustness and stability at the expense of routing
   dynamics and flexibility.  Evolution of robust and dynamic routing
   algorithms has since proved extraordinarily difficult, probably due
   more to varying perceptions of service requirements than to
   engineering problems.

   The original exterior-gateway model suggested in RFC-827 [1] and
   subsequently refined in RFC-888 [2] severely restricted the Internet
   topology essentially to a tree structure with root represented by the
   BBN-developed "core" gateway system.  The most important
   characteristic of the model was that debilitating resource-consuming
   routing loops between clusters of gateways (called autonomous

Mills                                                           [Page 1]



RFC 975                                                    February 1986
Autonomous Confederations

   systems) could not occur in a tree-structured topology.  However, the
   administrative and enforcement difficulties involved, not to mention
   the performance liabilities, made widespread implementation
   impractical.

   1.1.  The Exterior Gateway Protocol

      Requirements for near-term interoperability between the BBN core
      gateways and the remainder of the gateway population implemented
      by other organizations required that an interim protocol be
      developed with the capability of exchanging reachability
      information, but not necessarily the capability to function as a
      true routing algorithm. This protocol is called the Exterior
      Gateway Protocol (EGP) and is documented in RFC-904 [3].

      EGP was not designed as a routing algorithm, since no agreement
      could be reached on a trusted, common metric.  However, EGP was
      designed to provide high-quality reachability information, both
      about neighbor gateways and about routes to non-neighbor gateways.
      At the present state of development, dynamic routes are computed
      only by the core system and provided to non-core gateways using
      EGP only as an interface mechanism.  Non-core gateways can provide
      routes to the core system and even to other non-core gateways, but
      cannot pass on "third-party" routes computed using data received
      from other gateways.

      As operational experience with EGP has accumulated, it has become
      clear that a more decentralized dynamic routing capability is
      needed in order to avoid resource-consuming suboptimal routes.  In
      addition, there has long been resistance to the a-priori
      assumption of a single core system, with implications of
      suboptimal performance, administrative problems, impossible
      enforcement and possible subversion.  Whether or not this
      resistance is real or justified, the important technical question
      remains whether a more dynamic, distributed approach is possible
      without significantly diluting stability and robustness.

      This document proposes certain enhancements of EGP which
      generalize the concept of core system to include multiple
      communities of autonomous systems, called autonomous
      confederations.  Autonomous confederations maintain a higher