This article discusses how Bidirectional Forwarding Detection (BFD) for MPLS IPv4 Label Switched Paths (LSPs) operates based on the Routing Engine, rather than being distributed, and its implications for network performance and reliability.

You can configure Bidirectional Forwarding Detection (BFD) protocol on MPLS IPv4 LSPs as outlined in the Internet draft draft-ietf-bfd-mpls-02.txt, BFD for MPLS LSPs. BFD is used as a periodic Operation, Administration, and Maintenance (OAM) feature for LSPs to detect LSP data plane faults. You can configure BFD for LSPs that use either LDP or RSVP as the signaling protocol.

You can configure BFD for all of the RSVP LSPs on the router, a specific LSP, or the primary path of a specific LSP. To configure BFD for RSVP LSPs, include the oam and bfd-liveness-detection statements.

oam {

bfd-liveness-detection {

failure-action {

make-before-break teardown-timeout seconds;

teardown;

}

failure-action teardown;

minimum-interval milliseconds;

minimum-receive-interval milliseconds;

minimum-transmit-interval milliseconds;

multiplier detection-time-multiplier;

}

lsp-ping-interval time-interval;

lsp-ping-multiplier multiplier;

}

For configuration assistance on Bidirectional Forwarding Detection (BFD), please refer to the following resources: Bidirectional Forwarding Detection (BFD) for MPLS | Junos OS | Juniper Networks

BFD for MPLS IPv4 LSP is based on the Routing Engine and is not distributed. As a result, the minimum supported BFD timer interval is (100 ms * 3) per one LSP session, and for scaled LSP sessions, the minimum supported BFD timer interval is (300 ms * 3). As you increase the number of LSP sessions with BFD, you must also increase (scale) the interval timers to support the network. For Routing Engine switchover instances with nonstop active routing (NSR) support, the minimum supported BFD timer interval is (2.5 seconds * 3).