This KB provides information related to the seamless-BFD support for SRv6 TE on Juniper devices.

An SRv6 TE (Source packet routing IPv6 Traffic Engineering) tunnel is a collection of multiple/single path, each path consisting of multiple/single SID(s) (segment identifiers). These SID(s) steers traffic towards a TE path in a network to the destination. Each SID in the SRv6 TE tunnel path is considered as a hop to be visited by that path.

These SID(s) can reside at different nodes and the activeness of these SID(s) can change in a given network.

While provisioning an SRv6 TE tunnel at the ingress node the activeness of all the SID(s) [other than the first SID over which SRv6 TE tunnel resolves] in each path cannot be tracked normally. Thus, when a SID goes down in some transit node there can be traffic black-holing or delay in convergence as the ingress Node SRv6 TE module is unaware of what has gone wrong in the network and hence cannot react in real time.

This lack of reaction also restricts a backup path or in some cases tunnel of the same policy to override the current active tunnel leading to traffic loss.

To overcome the problem, sBFD mechanism over each path of a tunnel can be used to detect any failure in the TE paths.

With SRv6 TE tunnel’s each path configured with sBFD can now send probes to the destination of the path. These probes follow the hops or SIDs of the TE path. Any change/churn of any hops/SIDs in the path is reported as failures in the ingress. These failures are consumed in JUNOS and the SRv6 TE Tunnel path will be brought down. And hence the traffic can now be distributed on the remaining paths or backup paths or even backup tunnel of same policy.

sBFD for SRv6 TE is supported on JUNOS MX routers from version 24.4 and above.