When the pce-control option is enabled, the PCC delegates the control of the RSVP-TE LSP to the PCE.
The NRC-P sends a path update using the PCUpd message in the following cases:
a failure event that impacts a link or a node in the path of a PCE-controlled LSP
The operation is performed by the PCC as an MBB if the LSP remained in the up state because of protection provided by FRR or a secondary path. If the LSP went down, then the update brings it into the up state. A PCRpt message is sent by the PCC for each change to the state of the LSP during this process.
a topology change that impacts a link in the path of a PCE-controlled LSP
This topology change can be a change to the IGP metric, the TE metric, the admin group, or the SRLG membership of an interface. This update is performed as an MBB by the PCC.
the user performed a manual resignal of PCE-controlled RSVP-TE LSP path from the NRC-P
This update is performed as an MBB by the PCC.
the user performed a Global Concurrent Optimization (GCO) on a set of a PCE-controlled RSVP-TE LSPs from the NRC-P
This update is performed as an MBB by the PCC.
The procedures for the path update are the same as those for an SR-TE LSP. See LSP initiation for more information. However, the PCUpd message from the PCE does not contain the label for each hop in the computed ERO. PCC then signals the path using the ERO returned by the PCE and, if successful, programs the datapath, then sends the PCRpt message with the resulting RRO and hop labels provided by RSVP-TE signaling.
If the signaling of the ERO fails, then the ingress LER returns a PCErr message to PCE with the LSP error code field of the LSP-ERROR-CODE TLV set to a value of 8 (RSVP signaling error).
If an RSVP-TE LSP has the no adaptive option set, the ingress LER cannot perform an MBB for such an LSP. A PCUpd message received from the PCE is then failed by the ingress LER, which returns a PCErr message to PCE with the LSP Error code field of the LSP-ERROR-CODE TLV set to a value of 8 (RSVP signaling error).
When the NRC-P re-optimizes the path of a PCE-controlled RSVP-TE LSP, it is possible that a path that satisfies the constraints of the LSP no longer exists. In this case, the NRC-P sends a PCUpd message with an empty ERO, which forces the PCC to bring down the path of the RSVP-TE LSP.
The NRC-P sends a PCUpd message with an empty ERO if the following cases are true:
The requested bandwidth is the same as current bandwidth, which avoids bringing down the path on a resignal during a MBB transition.
Local protection is not currently in use, which avoids bringing down a path that activated an FRR backup path. The LSP can remain on the FRR backup path until a new primary path can be found by NRC-P.
The links of the current path are all operationally up, which allows NRC-P to ensure that the RSVP control plane reports the path down when a link is down and not prematurely bring the path down with an empty ERO.