BFD for RSVP

Background

When a Layer 2 device is deployed on a link between two RSVP nodes, an RSVP node can only use the Hello mechanism to detect a link fault. For example, on the network shown in Figure 1, a switch exists between P1 and P2. If a fault occurs on the link between the switch and P2, P1 keeps sending Hello packets and detects the fault after it fails to receive replies to the Hello packets. The fault detection latency causes seconds of traffic loss. To minimize packet loss, BFD for RSVP can be configured. BFD rapidly detects a fault and triggers TE FRR switching, which improves network reliability.

Figure 1 BFD for RSVP

Implementation

BFD for RSVP monitors RSVP neighbor relationships.

Unlike BFD for CR-LSP and BFD for TE that support multi-hop BFD sessions, BFD for RSVP establishes only single-hop BFD sessions between RSVP nodes to monitor the network layer.

BFD for RSVP, BFD for OSPF, BFD for IS-IS, and BFD for BGP can share a BFD session. When protocol-specific BFD parameters are set for a BFD session shared by RSVP and other protocols, the smallest values take effect. The parameters include the minimum intervals at which BFD packets are sent, minimum intervals at which BFD packets are received, and local detection multipliers.

Usage Scenario

BFD for RSVP applies to a network on which a Layer 2 device exists between the TE FRR point of local repair (PLR) on a bypass CR-LSP and an RSVP node on the primary CR-LSP.

Benefits

BFD for RSVP improves reliability on MPLS TE networks with Layer 2 devices.