RFC 1105 (rfc1105) - Page 1 of 17
Border Gateway Protocol (BGP)
Alternative Format: Original Text Document
Network Working Group K. Lougheed
Request for Comments: 1105 cisco Systems
Y. Rekhter
T.J. Watson Research Center, IBM Corp.
June 1989
A Border Gateway Protocol (BGP)
Status of this Memo
This RFC outlines a specific approach for the exchange of network
reachability information between Autonomous Systems.
At the time of this writing, the Border Gateway Protocol
implementations exist for cisco routers as well as for the NSFNET
Nodal Switching Systems. A public domain version for "gated" is
currently being implemented.
Distribution of this memo is unlimited.
1. 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 autonomous
systems (AS's) 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 policy
decisions at an AS level may be enforced.
BGP runs over a reliable transport level protocol. This eliminates
the need to implement explicit update fragmentation, retransmission,
acknowledgement, and sequencing. Any authentication scheme used by
the transport protocol may be used in addition to BGP's own
authentication mechanisms.
The initial BGP implementation is based on TCP [4], however any
reliable transport may be used. A message passing protocol such as
VMTP [5] might be more natural for BGP. TCP will be used, however,
since it is present in virtually all commercial routers and hosts.
In the following descriptions the phrase "transport protocol
connection" can be understood to refer to a TCP connection. BGP uses
TCP port 179 for establishing its connections.
Lougheed & Rekhter
