Label withdrawal delay timer

When an LDP session fails, the label associated with a FEC is withdrawn from all upstream peers. In addition, if the IGP adjusts the route for the FEC such that the current neighbor is no longer the next hop for the FEC, then the associated FEC label is withdrawn from all upstream peers.

The label withdrawal delay timer allows you to configure a delay to allow the IGP and LDP to converge after these events. The delay helps avoid sending the label withdraw message to the upstream peers. For example, after a link failure, instead of immediately sending a label withdraw to all upstream peers for the FEC, the delay allows the IGP to install a route which may match another existing downstream session. Label withdrawal from all upstream peers can be avoided if the FEC achieves a downstream label mapping which is consistent with the IGP routing table.

If the timer expires, the FEC label is withdrawn from all upstream peers.

Session down event

When a session becomes inactive, each DM for the session is deleted. This may cause LW to be sent upstream if the last installed DM is removed for a FEC. The behavior is as follows:

Route update event

When a route update for the FEC occurs, the installed DM may transition to retained if the next hop address for the FEC has changed. The behavior is as follows: