Exterior Gateway Protocol

The Exterior Gateway Protocol (EGP) is a routing protocol for the Internet originally defined in 1982 by Eric C. Rosen of Bolt, Beranek and Newman,[1] and formally specified in 1984 by David L. Mills.[2] Exterior Gateway Protocol (EGP) is a protocol for exchanging routing information between two neighbor gateway hosts (each with its own router) in a network of autonomous systems. EGP is commonly used between hosts on the Internet to exchange routing table information. The routing table contains a list of known routers, the addresses they can reach, and a cost metric associated with the path to each router so that the best available route is chosen. Each router polls its neighbor at intervals between 120 and 480 seconds and the neighbor responds by sending its complete routing table. EGP-2 is the latest version of EGP.

This article is about the specific protocol used on the early Internet. For routing protocols used to interconnect network systems, see Exterior gateway protocol.

History

EGP was developed by Bolt, Beranek and Newman in the early 1980s. It was first described in RFC 827[1] and formally specified in RFC 904.[2] EGP is a simple reachability protocol, and, unlike modern distance-vector and path-vector protocols, it is limited to tree-like topologies.

During the early days of the Internet, EGP version 3 (EGP3) was used to interconnect autonomous systems. RFC 1772 outlined a migration path from EGP to BGP.[3] Currently, BGP version 4 is the accepted standard for Internet routing and has essentially replaced the more limited EGP3.

References
  1. Rosen, Eric (October 1982). Exterior Gateway Protocol (EGP). IETF. doi:10.17487/RFC0827. RFC 827. Retrieved 2 Sep 2020.
  2. Mills, David (April 1984). Exterior Gateway Protocol Formal Specification. IETF. doi:10.17487/RFC0904. RFC 904. Retrieved 2 Sep 2020.
  3. Rekhter, Yakov; Gross, Phill (March 1995). Application of the Border Gateway Protocol in the Internet. IETF. doi:10.17487/RFC1772. RFC 1772. Retrieved 2 Sep 2020.

See also


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