An inter-Autonomous System (AS) protocol concerned with conveying routing reachability information between groups of routers that fall within a single administrative domain. EGP runs on top of the connectionless Internet Protocol (IP) and is assigned well-known port number 8.The Border Gateway Protocol (BGP), which builds on and enhances EGP, runs on top of the Transmission Control Protocol (TCP), thereby ensuring a connection-oriented data flow and reliability of datastream transport. EGP was described in IETF RFC 827 (1982). See also AS, BGP, connectionless, connection-oriented, domain, IETF, IP, port, protocol, routing, and TCP.
(1) (Exterior Gateway Protocol) A broad category of routing protocols that are designed to span different autonomous systems. Contrast with IGP.
(2) (Exterior Gateway Protocol) The original exterior gateway routing protocol (see above), which has been widely used in the U.S. Data Defense Network (DDN) and National Science Foundation Network (NSFNet). EGP is a distance vector protocol that uses polling to retrieve routing information. EGP has been superseded by BGP. See BGP and routing protocol.