BGP enables the Router to periodically send Keepalive packet to its peers for fault detection. Detecting a fault using this method takes more than 1 second. When traffic is transmitted at gigabit rates, second-level fault detection times cause significant packet loss. Association between BFD and the Border Gateway Protocol (BGP) enables BFD to quickly detect faults on links between BGP peers and report the faults to BGP, implementing fast BGP route convergence. Table 6-3 lists BGP convergence speed.

Application

Figure 6-10 BFD for BGP

In Figure 6-10, RouterA belongs to AS 100, and RouterB belongs to AS 200. RouterA and RouterB are directly connected and establish an External Border Gateway Protocol (EBGP) connection. BFD monitors the status of the EBGP connection between RouterA and RouterB. When the link between RouterA and RouterB becomes faulty, BFD can quickly detect the fault and notify BGP.