BGP stands for a Border Gateway Protocol. The lastest BGP version
is 4. It is referred as BGP-4. BGP-4 is one of the Exterior Gateway
Protocols and de-fact standard of Inter Domain routing protocol.
BGP-4 is described in
RFC1771 - A Border Gateway Protocol
Many extentions are added to
Multiprotocol Extensions for BGP-4 provide multiprotocol
support to BGP-4.