Practical BGP

Preface

“Experience is the best teacher” is a valuable truism in network design, especially in designing a routed network using a protocol as widespread, and as little understood, as the Border Gateway Protocol (BGP). It's hard to grasp BGP at a high level, because network engineers tend to see only a small piece of the system they are interacting with—either their connection to the Internet, or their network backbone, or some other slice. From this perspective, it's hard to understand how BGP works in the real world, and what impact decisions in one small slice of the network will actually have in the larger internetwork.

How, for instance, does BGP express policy? And what is the difference between a routing protocol that expresses policy versus ...