This feature enhances the procedures of the timer resignal and of the delay option of the manual resignal of the active path of a RSVP-TE LSP. The feature updates the administrative group information of the links of the current path and checks for administrative group constraint. MPLS performs the following sequence of actions.
CSPF checks the validity and updates the administrative group membership of the current active path. The validity of the path means that each TE link used by the path is still in the TE-DB, which ensures the continuous path form ingress to egress.
CSPF attempts a new path computation for the active path.
If CSPF returns a new path, MPLS performs the following actions.
If CSPF finds the current path is invalid, MPLS signals and programs the new path.
If the updated administrative group membership of the current path violates the path administrative group constraint, MPLS signals and programs the new path.
If the updated administrative group membership of current path does not violate the path administrative group constraint, MPLS signals the new path only if its cumulative metric is different from the updated cumulative metric of the current path.
If CSPF returns no path, MPLS keeps the current path regardless of whether the updated administrative group membership of the current path violates the path administrative group constraint.
This behavior of SR OS prevents unnecessary blackholing of traffic as a result of potential TE database churn, in which case a compliant path for the administrative group constraint is found at the next resignal timer expiry.