| BGP is an Exterior Gateway Protocol,
or EGP, which was developed to exchange routing information on very
large networks, such as the Internet. Generally, each network that connects to a large internetwork is owned and operated by a
different entity -- a company, university, government agency, or some
other independent group -- which may have unique routing and
security policies. Since each of these groups wish to maintain
autonomous control over their individual networks (systems), EGPs
serve to divide the internetwork up into a series of Autonomous Systems
(ASs). Each independent organization that connects to the internetwork typically represents one AS.
During the early days of the Internet, an exterior gateway
protocol called EGP version 3 (not to be confused with Exterior Gateway
Protocols in general) was used to interconnect these ASs. The
National Science Foundation Network (NSFNET) used EGP to exchange
reachability information between the backbone and the regional
networks. Although EGP was widely deployed, its topology
restrictions and inefficiency in dealing with routing loops and
setting routing policies created a need for a new and more robust
protocol -- so it was replaced with BGP. Currently, BGP version 4
(BGP4) is the
accepted standard for Internet routing.
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