BGP-4 Protocol Analysis
RFC 4274

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Network Working Group                                           D. Meyer
Request for Comments: 4274                                      K. Patel
Category: Informational                                    Cisco Systems
                                                            January 2006

                        BGP-4 Protocol Analysis

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The purpose of this report is to document how the requirements for
   publication of a routing protocol as an Internet Draft Standard have
   been satisfied by Border Gateway Protocol version 4 (BGP-4).

   This report satisfies the requirement for "the second report", as
   described in Section 6.0 of RFC 1264.  In order to fulfill the
   requirement, this report augments RFC 1774 and summarizes the key
   features of BGP-4, as well as analyzes the protocol with respect to
   scaling and performance.

Meyer & Patel                Informational                      [Page 1]
RFC 4274                BGP-4 Protocol Analysis             January 2006

Table of Contents

   1. Introduction ....................................................2
   2. Key Features and Algorithms of BGP ..............................3
      2.1. Key Features ...............................................3
      2.2. BGP Algorithms .............................................4
      2.3. BGP Finite State Machine (FSM) .............................4
   3. BGP Capabilities ................................................5
   4. BGP Persistent Peer Oscillations ................................6
   5. Implementation Guidelines .......................................6
   6. BGP Performance Characteristics and Scalability .................6
      6.1. Link Bandwidth and CPU Utilization .........................7
   7. BGP Policy Expressiveness and its Implications ..................9
      7.1. Existence of Unique Stable Routings .......................10
      7.2. Existence of Stable Routings ..............................11
   8. Applicability ..................................................12
   9. Acknowledgements ...............................................12
   10. Security Considerations .......................................12
   11. References ....................................................13
       11.1. Normative References ....................................13
       11.2. Informative References ..................................14

1.  Introduction

   BGP-4 is an inter-autonomous system routing protocol designed for
   TCP/IP internets.  Version 1 of BGP-4 was published in [RFC1105].
   Since then, BGP versions 2, 3, and 4 have been developed.  Version 2
   was documented in [RFC1163].  Version 3 is documented in [RFC1267].
   Version 4 is documented in [BGP4] (version 4 of BGP will hereafter be
   referred to as BGP).  The changes between versions are explained in
   Appendix A of [BGP4].  Possible applications of BGP in the Internet
   are documented in [RFC1772].

   BGP introduced support for Classless Inter-Domain Routing (CIDR)
   [RFC1519].  Because earlier versions of BGP lacked the support for
   CIDR, they are considered obsolete and unusable in today's Internet.

   The purpose of this report is to document how the requirements for
   publication of a routing protocol as an Internet Draft Standard have
   been satisfied by Border Gateway Protocol version 4 (BGP-4).

   This report satisfies the requirement for "the second report", as
   described in Section 6.0 of [RFC1264].  In order to fulfill the
   requirement, this report augments [RFC1774] and summarizes the key
   features of BGP-4, as well as analyzes the protocol with respect to
   scaling and performance.

Meyer & Patel                Informational                      [Page 2]
RFC 4274                BGP-4 Protocol Analysis             January 2006

2.  Key Features and Algorithms of BGP

   This section summarizes the key features and algorithms of BGP.  BGP
   is an inter-autonomous system routing protocol; it is designed to be
   used between multiple autonomous systems.  BGP assumes that routing
   within an autonomous system is done by an intra-autonomous system
   routing protocol.  BGP also assumes that data packets are routed from
   source towards destination independent of the source.  BGP does not
   make any assumptions about intra-autonomous system routing protocols
   deployed within the various autonomous systems.  Specifically, BGP
   does not require all autonomous systems to run the same intra-
   autonomous system routing protocol (i.e., interior gateway protocol
   or IGP).

   Finally, note that BGP is a real inter-autonomous system routing
   protocol; and, as such, it imposes no constraints on the underlying