Ordinarily, routers within an AS would be configured in a full mesh. Route reflectors and confederations, though, enable routing information to be redistributed to all routers within an AS while minimizing the amount of peering required. These features reduce the number of TCP sessions that must be maintained, lowering network overhead and CPU and memory requirements. Certain routers within an AS can be designated as route reflectors. Rather than each client requiring a connection to the other clients, each client receives its updates directly from the route reflector, minimizing the number of TCP sessions required for information to be distributed.
Confederations can serve as an alternative or a complement to route reflectors.
The confederation feature enables network administrators to break up ASs into logical sub-ASs. Within confederations, route reflectors can be used to further streamline the BGP network, if desired. Route reflectors can be configured in a redundant fashion, with each client physically connected to two route reflectors to ensure that BGP information continues to be reflected if there is a problem with one route reflector. The redundant configuration increases the number of physical TCP connections required compared to the single-route reflector configuration, but still significantly streamlines the network topology compared with a full network mesh. Using route reflection, network operators can migrate from a full mesh to a partial mesh without affecting network service.