BGP Topology

In the preceding section, I boiled down the function of BGP into this summary: the exchange of network reachability information between ASes of routers and networks, and the determination of routes from this information. The actual method that BGP uses to accomplish this, however, is fairly complex.

One of the most important characteristics of BGP is its flexibility. The protocol can connect together any internetwork of ASes using an arbitrary topology. The only requirement is that each AS have at least one router that is able to run BGP and that this router connect to at least one other AS's BGP router. Beyond that, "the sky is the limit," as they say. BGP can handle a set of ASes connected in a full mesh topology (each AS to each ...

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