RFC 1092 (rfc1092) - Page 1 of 5

EGP and policy based routing in the new NSFNET backbone

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Network Working Group                                         J. Rekhter
Request for Comments: 1092                  T. J. Watson Research Center
                                                           February 1989


        EGP and Policy Based Routing in the New NSFNET Backbone

Status of this Memo

   This memo discusses implementation decisions for routing issues in
   the NSFNET, especially in the NSFNET Backbone.  Of special concern is
   the restriction of routing information to advertize the best route as
   established by a policy decision.  Distribution of this memo is
   unlimited.

Introduction

   The NSFNET backbone routes packets between the Regionals Networks to
   which it is connected, (i.e., the packets arriving at a backbone
   entry node are routed to an exit node).  How they travel through the
   network is determined by two components:

     the NSFNET backbone routing protocol/algorithm, and

     additional information about the externally connected networks.

   This paper is concerned with how reachability information between the
   external networks and the NSFNET backbone is exchanged so that
   packets can be routed to the correct destination by using a
   reasonable path.

EGP as reachability protocol

   The EGP (Exterior Gateway Protocol) routing method will be used to
   exchange reachability information between the NSFNET backbone and the
   regional networks.

   There are several problems with using EGP as a reachability protocol
   for routing in a meshed environment.  Some EGP components require
   further definitions for the NSFNET backbone - regional network
   interactions.  It should be noted that the use of EGP is only viewed
   as an interim measure until better inter autonomous system protocols
   are defined and widely deployed for gateways used by regional
   networks.

   The following is a list of some EGP problems and issues:

      The EGP model assumes an engineered spanning tree topology,



Rekhter
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