Open Standards

Border Gateway Protocol (BGP)

From Sketches on Napkins to Border Gateway Protocol


Server room

Cisco Fellow Kirk Lougheed’s Border Gateway Protocol (BGP) is one of many Cisco contributions to Internet standards. BGP is a path vector protocol for exchanging routing information between independent networks and has been adopted by most Internet Service Providers (ISPs).

At Internet Engineering Task Force (IETF) meetings in January 1989, Lougheed (a Cisco founder and employee number four) and Yakov Rekhter of IBM sketched their first draft of the protocol “on cafeteria napkins,” which are preserved as framed artifacts of Cisco’s role in standards development in one of the headquarters buildings in San Jose.

BGP facilitates scalable, fully decentralized routing, replacing the Exterior Gateway Protocol (EGP) routing protocol. Len Bosack, a Cisco founder, suggested reusing Transmission Control Protocol (TCP) as a reliable way to carry routing information. Lougheed commented that this suggestion “was considered heresy at the time.”  Lougheed, Rekhter, and their IETF colleagues incorporated this suggestion and other refinements into BGP, eventually producing three successive versions of the protocol.  Later, Rekhter collaborated with Tony Li on BGP-4, which supports classless inter-domain routing to allocate network addresses more efficiently than the original network address assignment scheme. Released in 1995, this latest version of BGP continues to be used today by all large ISPs.

Each instance of a BGP router maintains a table of networks, and each network is associated with a path of autonomous systems (roughly, groups of networks in a single administrative domain) that must be traversed to reach that network. BGP specifies how these tables of networks are exchanged between routers, subject to administrator-defined policies. The result is a global view of all networks within the Internet.  BGP is the standard for communicating network reachability information within the Internet core.

In 1997, Cisco recognized Lougheed’s achievement by naming him a Cisco Fellow, chosen for innovative technical contributions and leadership and for advancing the networking industry. Many Cisco Fellows significantly influenced the evolution of IP networking and are widely recognized as thought leaders in the networking industry.