Network Working Group Y. Rekhter
Request for Comments: 1772 T.J. Watson Research Center, IBM Corp.
Obsoletes: 1655 P. Gross
Category: Standards Track MCI
Application of the Border Gateway Protocol in the Internet
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.
This document, together with its companion document, "A Border
Gateway Protocol 4 (BGP-4)", define an inter-autonomous system
routing protocol for the Internet. "A Border Gateway Protocol 4
(BGP-4)" defines the BGP protocol specification, and this document
describes the usage of the BGP in the Internet.
Information about the progress of BGP can be monitored and/or
reported on the BGP mailing list (firstname.lastname@example.org).
This document was originally published as RFC 1164 in June 1990,
jointly authored by Jeffrey C. Honig (Cornell University), Dave Katz
(MERIT), Matt Mathis (PSC), Yakov Rekhter (IBM), and Jessica Yu
The following also made key contributions to RFC 1164 -- Guy Almes
(ANS, then at Rice University), Kirk Lougheed (cisco Systems), Hans-
Werner Braun (SDSC, then at MERIT), and Sue Hares (MERIT).
We like to explicitly thank Bob Braden (ISI) for the review of the
previous version of this document.
This updated version of the document is the product of the IETF BGP
Working Group with Phill Gross (MCI) and Yakov Rekhter (IBM) as
Rekhter & Gross [Page 1]RFC 1772 BGP-4 Application March 1995
John Moy (Proteon) contributed Section 7 "Required set of supported
Scott Brim (Cornell University) contributed the basis for Section 8
"Interaction with other exterior routing protocols".
Most of the text in Section 9 was contributed by Gerry Meyer
Parts of the Introduction were taken almost verbatim from .
We would like to acknowledge Dan Long (NEARNET) and Tony Li (cisco
Systems) for their review and comments on the current version of the
The work of Yakov Rekhter was supported in part by the National
Science Foundation under Grant Number NCR-9219216.
This memo describes the use of the Border Gateway Protocol (BGP) 
in the Internet environment. BGP is an inter-Autonomous System
routing protocol. The network reachability information exchanged via
BGP provides sufficient information to detect routing loops and
enforce routing decisions based on performance preference and policy
constraints as outlined in RFC 1104 . In particular, BGP exchanges
routing information containing full AS paths and enforces routing
policies based on configuration information.
As the Internet has evolved and grown over in recent years, it has
become painfully evident that it is soon to face several serious
scaling problems. These include:
- Exhaustion of the class-B network address space. One
fundamental cause of this problem is the lack of a network
class of a size which is appropriate for mid-sized
organization; class-C, with a maximum of 254 host addresses, is
too small while class-B, which allows up to 65534 addresses, is
too large to be densely populated.
- Growth of routing tables in Internet routers are beyond the
ability of current software (and people) to effectively manage.
- Eventual exhaustion of the 32-bit IP address space.
It has become clear that the first two of these problems are likely
to become critical within the next one to three years. Classless
inter-domain routing (CIDR) attempts to deal with these problems by
Rekhter & Gross [Page 2]RFC 1772 BGP-4 Application March 1995
proposing a mechanism to slow the growth of the routing table and the
need for allocating new IP network numbers. It does not attempt to
solve the third problem, which is of a more long-term nature, but
instead endeavors to ease enough of the short to mid-term