Interworking Between BFD and OSPF

This section describes the application scenario of interworking between BFD and OSPF.

Applicable Environment

A link fault or the change of topology may lead to rerouting in a network. The short-duration convergence of a routing protocol is important for the improvement of availability of the network. A feasible solution is to fast detect the fault and notify the fault to the routing protocol immediately.

In the BFD-OSPF interworking, OSPF is associated with a BFD session. The BFD session fast detects a link fault and notifies OSPF of the fault. In this manner, OSPF speeds up the response to the change of the network topology.

Table 1 shows statistics of convergence speeds when OSPF is and is not associated with a BFD session.

**Table 1** Statistics of OSPF convergence speeds
Associated with BFD or Not	Link Fault Detection Mechanism	Convergence Speed
Not associated with BFD	Timeout of the OSPF Hello keepalive timer	At the second level
Associated with BFD	BFD session in the Down state	At the millisecond level

Typical Application

As shown in Figure 1, OSPF runs among Router_A, Router_B, and Router_C which are mutual neighbors. The link from Router_A to Router_B serves as the active link whereas the link from Router_A to Router_C to Router_B serves as the standby link.

Create a BFD session on the link between Router_A and Router_B. Therefore, when the link status changes, the convergence speed of OSPF increases. If the link between Router_A and Router_B fails, BFD rapidly identifies the fault and notifies OSPF of the fault. Therefore, the service traffic is switched to the standby link.

Figure 1 Networking diagram of BFD-OSPF interworking