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The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  TCP/IP Routing Protocols (Gateway Protocols)                 9  TCP/IP Exterior Gateway/Routing Protocols (BGP and EGP)                      9  TCP/IP Border Gateway Protocol (BGP/BGP-4)

TCP/IP Border Gateway Protocol (BGP/BGP-4) 1 BGP Overview, History, Standards and Versions

If you were to ask the average Internet user, or even that typical network administrator, to make a list of the ten most important TCP/IP protocols, it's probable that BGP wouldn't often show up. Routing protocols are “worker bees” of the TCP/IP suite and just not very exciting. The reality, however, is that BGP is a critically important protocol to the operation of larger internetworks and the Internet itself. It is the “glue” that binds smaller internetworks (autonomous systems) together, and it ensures that every organization is able to share routing information. It is this function that lets us take disparate networks and internetworks and find efficient routes from any host to any other host, regardless of location.

In this section I begin our look at the very important BGP protocol by covering its basic concepts and general operation. I start, as usual, with an overview of the protocol and discussion of its history, standards and versions, including a discussion of its key features and characteristics. I then cover basic operational concepts, including topology, the notion of BGP speakers and neighbor relationships. I discuss BGP traffic types and how policies can be used to control traffic flows on the internetwork. I explain how BGP routers store and advertise routes, and the function of Routing Information Bases (RIBs). I describe the basic algorithm used by BGP and how path attributes describe routes. I then provide a summary of how the BGP route selection process operates. I conclude with a general description of BGP's operation and its high-level use of various messages.

TCP/IP Border Gateway Protocol (BGP/BGP-4) 1 BGP Overview, History, Standards and Versions