Border Gateway Protocol (BGP)
RFC 1163

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Network Working Group                                        K. Lougheed
Request for Comments: 1163                                 cisco Systems
Obsoletes: RFC 1105                                           Y. Rekhter
                                   T.J. Watson Research Center, IBM Corp
                                                               June 1990

                    A Border Gateway Protocol (BGP)

Status of this Memo

   This RFC, together with its companion RFC-1164, "Application of the
   Border Gateway Protocol in the Internet", define a Proposed Standard
   for an inter-autonomous system routing protocol for the Internet.

   This protocol, like any other at this initial stage, may undergo
   modifications before reaching full Internet Standard status as a
   result of deployment experience.  Implementers are encouraged to
   track the progress of this or any protocol as it moves through the
   standardization process, and to report their own experience with the
   protocol.

   This protocol is being considered by the Interconnectivity Working
   Group (IWG) of the Internet Engineering Task Force (IETF).
   Information about the progress of BGP can be monitored and/or
   reported on the IWG mailing list (IWG@nri.reston.va.us).

   Please refer to the latest edition of the "IAB Official Protocol
   Standards" RFC for current information on the state and status of
   standard Internet protocols.

   Distribution of this memo is unlimited.

Table of Contents

      1.  Acknowledgements......................................    2
      2.  Introduction..........................................    2
      3.  Summary of Operation..................................    4
      4.  Message Formats.......................................    5
      4.1 Message Header Format.................................    5
      4.2 OPEN Message Format...................................    6
      4.3 UPDATE Message Format.................................    8
      4.4 KEEPALIVE Message Format..............................   10
      4.5 NOTIFICATION Message Format...........................   10
      5.  Path Attributes.......................................   12
      6.  BGP Error Handling....................................   14
      6.1 Message Header error handling.........................   14
      6.2 OPEN message error handling...........................   15

Lougheed & Rekhter                                              [Page 1]
RFC 1163                          BGP                          June 1990

      6.3 UPDATE message error handling.........................   16
      6.4 NOTIFICATION message error handling...................   17
      6.5 Hold Timer Expired error handling.....................   17
      6.6 Finite State Machine error handling...................   18
      6.7 Cease.................................................   18
      7.  BGP Version Negotiation...............................   18
      8.  BGP Finite State machine..............................   18
      9.  UPDATE Message Handling...............................   22
      10. Detection of Inter-AS Policy Contradictions...........   23
      Appendix 1.  BGP FSM State Transitions and Actions........   25
      Appendix 2.  Comparison with RFC 1105.....................   28
      Appendix 3.  TCP options that may be used with BGP........   28
      References................................................   29
      Security Considerations...................................   29
      Authors' Addresses........................................   29

1.  Acknowledgements

   We would like to express our thanks to Guy Almes (Rice University),
   Len Bosack (cisco Systems), Jeffrey C. Honig (Cornell Theory Center)
   and all members of the Interconnectivity Working Group of the
   Internet Engineering Task Force, chaired by Guy Almes, for their
   contributions to this document.

   We would also like to thank Bob Hinden, Director for Routing of the
   Internet Engineering Steering Group, and the team of reviewers he
   assembled to review earlier versions of this document.  This team,
   consisting of Deborah Estrin, Milo Medin, John Moy, Radia Perlman,
   Martha Steenstrup, Mike St. Johns, and Paul Tsuchiya, acted with a
   strong combination of toughness, professionalism, and courtesy.

2.  Introduction

   The Border Gateway Protocol (BGP) is an inter-Autonomous System
   routing protocol.  It is built on experience gained with EGP as
   defined in RFC 904 [1] and EGP usage in the NSFNET Backbone as
   described in RFC 1092 [2] and RFC 1093 [3].

   The primary function of a BGP speaking system is to exchange network
   reachability information with other BGP systems.  This network
   reachability information includes information on the full path of
   Autonomous Systems (ASs) that traffic must transit to reach these
   networks.  This information is sufficient to construct a graph of AS
   connectivity from which routing loops may be pruned and some policy