IGP SR Adjacency SID Hold-Time

This feature introduces a configurable hold time for interior gateway protocol (IGP) segment routing adjacency segment ID (Adj-SID) to ensure that the IGP does not release the Adj-SIDs immediately after a link flaps or goes down but retains them for the configured hold-time duration. The default hold time is 300 seconds for Adj-SIDs in the IS-IS protocol, and 180 seconds for the OSPF protocol. The IS-IS protocol creates Adj-SIDs per adjacency, level, and address family (one each for IPv4 and IPv6). An MPLS label is allocated for each Adj-SID that gets created. These labels are allocated after the adjacency status of the segment changes to the up state. The OSPF protocol creates Adj-SIDs per adjacency. To ensure Adj-SIDs are retained during adjacency or link flaps, the Adj-SIDs are not released immediately when the link goes down.