BGP-4 Protocol Document Roadmap and Implementation Experience (RFC1656)
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2019-Feb-12
Internet Society Requests For Comment (RFCs)
Border Gateway Protocol v4 (BGP-4)  is an inter-Autonomous System routing protocol. It is built on experience gained with BGP as defined in RFC-1267  and BGP usage in the connected Internet as described in RFC-1268 . This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind.
Network Working Group P. Traina Request for Comments: 1656 cisco Systems Category: Informational July 1994
BGP-4 Protocol Document Roadmap and Implementation Experience
Status of this Memo
This memo provides information for the Internet community. This memo does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Border Gateway Protocol v4 (BGP-4)  is an inter-Autonomous System routing protocol. It is built on experience gained with BGP as defined in RFC-1267  and BGP usage in the connected Internet as described in RFC-1268 .
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 inter-domain 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 .
The management information base has been defined  and security considerations are discussed in the protocol definition document .
Applicability Statement for BGP-4
BGP-4 is explicitly designed for carrying reachability information between Autonomous Systems. BGP-4 is not intended to replace interior gateway protocols such as OSPF  or RIP .
Four vendors have developed independent implementations at the time of this memo:
Traina [Page 1]
RFC 1656 BGP-4 Implementation July 1994
ANS (gated) Europanet 3COM cisco
The complete interoperability matrix between all known implementations of various versions of BGP is available under separate cover .
One implementation has been extensively tested in a network designed to mirror the complex connectivity present at many major Internet borders. This network consists of multiple BGP-3 and BGP-4 speakers carrying full routing information injected from Alternet, EBone, Sprint, CERFnet, and cisco. In many cases additional AS adjacencies are simulated via the use of IP over IP tunnels to increase the complexity of the routing topology.
The primary feature of BGP-4 is the ability to carry network reachability information without regard to classfull routing. In addition to canonical routing information, CIDR prefixes (both supernets and subnets) are being injected from IGP information and aggregated using the methods described in BGP-4. AS set aggregation and policy decisions based upon AS sets have been tested.
Secondary extensions incorporated as part of version 4 of this protocol include e...