Practical BGP

Timers

All routing protocols have timers, used to determine when an apparently inactive peering relationship should be dropped and the routes learned through that peering relationship should be no longer used. Routing protocols also have timers to prevent a network from never converging when faced with rapid changes in the network topology. We will examine both types of timers in the following sections.

Hold and Keepalive Timers

The hold and keepalive timers in BGP provide a simple test for peer aliveness. Since a BGP speaker only transmits information when its local databases change, there are no regular messages transmitted between two BGP peers. If a BGP speaker fails, there's no reason its peers should know it has failed, since a failure ...