RFC 1966 (rfc1966) - Page 1 of 7

BGP Route Reflection An alternative to full mesh IBGP

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Network Working Group                                           T. Bates
Request for Comments: 1966                                 cisco Systems
Category: Experimental                                        R. Chandra
                                                           cisco Systems
                                                               June 1996


                          BGP Route Reflection
                    An alternative to full mesh IBGP

Status of this Memo

   This memo defines an Experimental Protocol for the Internet
   community.  This memo does not specify an Internet standard of any
   kind.  Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Abstract

   The Border Gateway Protocol [1] is an inter-autonomous system routing
   protocol designed for TCP/IP internets. BGP deployments are
   configured such that that all BGP speakers within a single AS must be
   fully meshed so that any external routing information must be re-
   distributed to all other routers within that AS. This represents a
   serious scaling problem that has been well documented with several
   alternatives proposed [2,3].

   This document describes the use and design of a method known as
   "Route Reflection" to alleviate the the need for "full mesh" IBGP.

1.  Introduction

   Currently in the Internet, BGP deployments are configured such that
   that all BGP speakers within a single AS must be fully meshed and any
   external routing information must be re-distributed to all other
   routers within that AS. This "full mesh" requirement clearly does not
   scale when there are a large number of IBGP speakers as is common in
   many of todays internet networks.

   For n BGP speakers within an AS you must maintain n*(n-1)/2 unique
   IBGP sessions. With finite resources in both bandwidth and router CPU
   this clearly does not scale.

   This scaling problem has been well documented and a number of
   proposals have been made to alleviate this [2,3]. This document
   represents another alternative in alleviating the need for a "full
   mesh" and is known as "Route Reflection". It represents a change in
   the commonly understood concept of IBGP and the addition of two new



Bates & Chandra               Experimental
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