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
4 (BGP-4).
Many extentions are added to RFC1771. RFC2858 -
Multiprotocol Extensions for BGP-4 provide multiprotocol
support to BGP-4.