BGP Detailed Messaging, Operation, and Message Formats
So far, I have discussed the concepts and general operation of the BGP. To get a better understanding of exactly how BGP works, it is helpful to take a detailed look at its four different message types—Open, Update, Keepalive, and Notification—and how they are used. As we do this, we can examine the fields in each message type, so that you can comprehend not just the way that messaging is accomplished, but the way that routing data is actually communicated. Let's begin with a description of common attributes of BGP message generation and transport, and the general format used for all BGP messages.
BGP Message Generation and Transport
Each router running BGP generates messages to implement the ...