A Border Gateway Protocol 4 (BGP-4)
RFC 1771
Document | Type |
RFC - Draft Standard
(March 1995; Errata)
Obsoleted by RFC 4271
Obsoletes RFC 1654
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Authors | |||
Last updated | 2020-01-21 | ||
Stream | Legacy | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1771 (Draft Standard) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group Y. Rekhter Request for Comments: 1771 T.J. Watson Research Center, IBM Corp. Obsoletes: 1654 T. Li Category: Standards Track cisco Systems Editors March 1995 A Border Gateway Protocol 4 (BGP-4) 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. Abstract This document, together with its companion document, "Application of the Border Gateway Protocol in the Internet", define an inter- autonomous system routing protocol for the Internet. 1. Acknowledgements This document was originally published as RFC 1267 in October 1991, jointly authored by Kirk Lougheed (cisco Systems) and Yakov Rekhter (IBM). We would like to express our thanks to Guy Almes (ANS), Len Bosack (cisco Systems), and Jeffrey C. Honig (Cornell University) for their contributions to the earlier version of this document. We like to explicitly thank Bob Braden (ISI) for the review of the earlier version of this document as well as his constructive and valuable comments. 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 the previous version (BGP-2) 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. Rekhter & Li [Page 1] RFC 1771 BGP-4 March 1995 This updated version of the document is the product of the IETF IDR Working Group with Yakov Rekhter and Tony Li as editors. Certain sections of the document borrowed heavily from IDRP [7], which is the OSI counterpart of BGP. For this credit should be given to the ANSI X3S3.3 group chaired by Lyman Chapin (BBN) and to Charles Kunzinger (IBM Corp.) who was the IDRP editor within that group. We would also like to thank Mike Craren (Proteon, Inc.), Dimitry Haskin (Bay Networks, Inc.), John Krawczyk (Bay Networks, Inc.), and Paul Traina (cisco Systems) for their insightful comments. We would like to specially acknowledge numerous contributions by Dennis Ferguson (MCI). The work of Yakov Rekhter was supported in part by the National Science Foundation under Grant Number NCR-9219216. 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 list of Autonomous Systems (ASs) that reachability information traverses. This information is sufficient to construct a graph of AS connectivity from which routing loops may be pruned and some policy decisions at the AS level may be enforced. BGP-4 provides a new set of mechanisms for supporting classless interdomain routing. These mechanisms include support for advertising an IP prefix and eliminates the concept of network "class" within BGP. BGP-4 also introduces mechanisms which allow aggregation of routes, including aggregation of AS paths. These changes provide support for the proposed supernetting scheme [8, 9]. To characterize the set of policy decisions that can be enforced using BGP, one must focus on the rule that a BGP speaker advertise to its peers (other BGP speakers which it communicates with) in neighboring ASs only those routes that it itself uses. This rule reflects the "hop-by-hop" routing paradigm generally used throughout the current Internet. Note that some policies cannot be supported by the "hop-by-hop" routing paradigm and thus require techniques such as source routing to enforce. For example, BGP does not enable one AS to send traffic to a neighboring AS intending that the traffic take a different route from that taken by traffic originating in the Rekhter & Li [Page 2] RFC 1771 BGP-4 March 1995Show full document text