Chapter 2. How BGP Has Been Adapted to the Data Center
Before its use in the data center, BGP was primarily, if not exclusively, used in service provider networks. As a consequence of its primary use, operators cannot use BGP inside the data center in the same way they would use it in the service provider world. If you’re a network operator, understanding these differences and their reason is important in preventing misconfiguration.
The dense connectivity of the data center network is a vastly different space from the relatively sparse connectivity between administrative domains. Thus, a different set of trade-offs are relevant inside the data center than between data centers. In the service provider network, stability is preferred over rapid notification of changes. So, BGP typically holds off sending notifications about changes for a while. In the data center network, operators want routing updates to be as fast as possible. Another example is that because of BGP’s default design, behavior, and its nature as a path-vector protocol, a single link failure can result in an inordinately large number of BGP messages passing between all the nodes, which is best avoided. A third example is the default behavior of BGP to construct a single best path when a prefix is learned from many different Autonomous System Numbers (ASNs), because an ASN typically represents a separate administrative domain. But inside the data center, we want multiple paths to be selected.
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