BFD echo mode and operation details

When using Bidirectional Forwarding Detection (BFD), you can use what is called echo mode. The details of this mode can be found below:

• Echo packets are sent by the forwarding engine and forwarded back along the same path in order to perform detection
• The BFD session at the other end does not participate in the actual forwarding of the echo packets.
• The echo function and the forwarding engine are responsible for the detection process, therefore the number of BFD control packets that are sent out between two BFD neighbors is reduced.
• Since the forwarding engine is testing the forwarding path on the remote (neighbor) system without involving the remote system, there is an opportunity to improve the interpacket delay variance, thereby achieving quicker failure detection times than when not using echo mode and using only the BFD control packets for the BFD session.

Links:

https://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fs_bfd.html#wp1236440

https://forum.networklessons.com/t/bidirectional-forwarding-detection-bfd/1280/70?u=lagapides