Autonomous System Confederations for BGP
RFC 3065

Network Working Group                                          P. Traina
Request for Comments: 3065                        Juniper Networks, Inc.
Obsoletes: 1965                                             D. McPherson
Category: Standards Track                           Amber Networks, Inc.
                                                              J. Scudder
                                                     Cisco Systems, Inc.
                                                           February 2001

                Autonomous System Confederations for BGP

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 (2001).  All Rights Reserved.

Abstract

   The Border Gateway Protocol (BGP) is an inter-autonomous system
   routing protocol designed for Transmission Control Protocol/Internet
   Protocol (TCP/IP) networks.  BGP requires that all BGP speakers
   within a single autonomous system (AS) must be fully meshed.  This
   represents a serious scaling problem that has been well documented in
   a number of proposals.

   This document describes an extension to BGP which may be used to
   create a confederation of autonomous systems that is represented as a
   single autonomous system to BGP peers external to the confederation,
   thereby removing the "full mesh" requirement.  The intention of this
   extension is to aid in policy administration and reduce the
   management complexity of maintaining a large autonomous system.

1. Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC 2119].

Traina, et al.              Standards Track                     [Page 1]
RFC 3065        Autonomous System Confederations for BGP   February 2001

2. Introduction

   As currently defined, BGP requires that all BGP speakers within a
   single AS must be fully meshed.  The result is that for n BGP
   speakers within an AS n*(n-1)/2 unique IBGP sessions are required.
   This "full mesh" requirement clearly does not scale when there are a
   large number of IBGP speakers within the autonomous system, as is
   common in many networks today.

   This scaling problem has been well documented and a number of
   proposals have been made to alleviate this [3,5].  This document
   represents another alternative in alleviating the need for a "full
   mesh" and is known as "Autonomous System Confederations for BGP", or
   simply, "BGP Confederations".  It can also be said the BGP
   Confederations MAY provide improvements in routing policy control.

   This document is a revision of RFC 1965 [4] and it includes editorial
   changes, clarifications and corrections based on the deployment
   experience with BGP Confederations.  These revisions are summarized
   in Appendix A.

3. Terms and Definitions

   AS Confederation

      A collection of autonomous systems advertised as a single AS
      number to BGP speakers that are not members of the confederation.

   AS Confederation Identifier

      An externally visible autonomous system number that identifies the
      confederation as a whole.

   Member-AS

      An autonomous system that is contained in a given AS
      confederation.

   Member-AS Number

      An autonomous system number visible only internal to a BGP
      confederation.

4. Discussion

   It may be useful to subdivide autonomous systems with a very large
   number of BGP speakers into smaller domains for purposes of
   controlling routing policy via information contained in the BGP

Traina, et al.              Standards Track                     [Page 2]
RFC 3065        Autonomous System Confederations for BGP   February 2001

   AS_PATH attribute.  For example, one may choose to consider all BGP
   speakers in a geographic region as a single entity.  In addition to
   potential improvements in routing policy control, if techniques such
   as those presented here or in [5] are not employed, [1] requires BGP
   speakers in the same autonomous system to establish a full mesh of
   TCP connections among all speakers for the purpose of exchanging