An inter-Autonomous System (AS) protocol like the Exterior Gateway Protocol (EGP), BGP is concerned with conveying routing reachability information between groups of routers that fall within a single administrative domain. Although EGP runs on top of the Internet Protocol (IP), BGP runs on top of the Transmission Control Protocol (TCP), thereby ensuring a connection-oriented data flow and reliability of datastream transport.The IETF described the current version, BGP-4, in RFC 1771. BGP is assigned TCP well-known port number 179 and supports Classless InterDomain Routing (CIDR). See also AS, CIDR, connection-oriented, domain, EGP, IETF, IP, port, protocol, routing, TCP, and well-known port.
(1) See also BPG.
(2) (Border Gateway Protocol) The routing protocol that is used to span autonomous systems on the Internet. It is a robust, sophisticated and scalable protocol that was developed by the Internet Engineering Task Force (IETF). BGP4 supports the CIDR addressing scheme, which increased the number of available IP addresses on the Internet. A path vector protocol, BGP was designed to supersede EGP, the original exterior gateway protocol. See autonomous system, CIDR and routing protocol.