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BGP Route Reflection - An Alternative to Full Mesh IBGP (RFC2796)

IP.com Disclosure Number: IPCOM000003395D
Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2019-Feb-10
Document File: 11 page(s) / 13K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

T. Bates: AUTHOR [+2]

Related Documents

10.17487/RFC2796: DOI

Abstract

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

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Network Working Group T. Bates Request for Comments: 2796 Cisco Systems Updates: 1966 R. Chandra Category: Standards Track E. Chen Redback Networks April 2000

BGP Route Reflection - An Alternative to Full Mesh IBGP

Status of this Memo

This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (2000). All Rights Reserved.

Abstract

The Border Gateway Protocol [1] is an inter-autonomous system routing protocol designed for TCP/IP internets. Currently in the Internet 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. For n BGP speakers within an AS that requires to maintain n*(n-1)/2 unique IBGP sessions. This "full mesh" requirement clearly does not scale when there are a large number of IBGP speakers each exchanging a large volume of routing information, as is common in many of todays internet networks.

Bates, et al. Standards Track [Page 1]

RFC 2796 BGP Route Reflection April 2000

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". This approach allows a BGP speaker (known as "Route Reflector") to advertise IBGP learned routes to certain IBGP peers. It represents a change in the commonly understood concept of IBGP, and the addition of two new optional transitive BGP attributes to prevent loops in routing updates.

This document is a revision of RFC1966 [4], and it includes editorial changes, clarifications and corrections based on the deployment experience with route reflection. These revisions are summarized in the Appendix.

2. Design Criteria

Route Reflection was designed to satisfy the following criteria.

o Simplicity

Any alternative must be both simple to configure as well as understand.

o Easy Transition

It must be possible to transition from a full mesh configuration without the need to change either topology or AS. This is an unfortunate management overhead of the technique proposed in [3].

o Compatibility ...

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