All MBB types are supported for PCE-computed LSPs. The LSP MBB procedures for a PCE-computed LSP (pce-computation enabled and pce-control disabled) are as follows.
The PCC issues a PCReq for the same PLSP-ID and includes the updated constraints in the metric, LSPA, and bandwidth objects.
If the PCE successfully finds a path, it replies with a PCRep message with the ERO.
If the PCE does not find a path, it replies with a PCRep message containing the No-Path object.
If the PCE returns a path, the PCC signals the LSP with the RSVP control plane and moves traffic to the new MBB path. If pce-report is enabled for this LSP, the PCC sends a PCRpt message with the delegation D-bit clear to retain control and containing the RRO and LSP objects, with the LSP-IDENTIFIERS TLV containing the LSP-ID of the new MBB path. The message includes the metric, LSPA, and bandwidth objects where the P-flag is clear, which indicates the operational values of these parameters. Unless the user disables the report-path-constraints option under the pcc context, the PCC also includes a second set of metric, LSPA, and bandwidth objects with the P-flag set to convey to the PCE the constraints of the path.
If the PCE returns no path or the RSVP-TE signaling of the returned path fails, MPLS puts the LSP into retry mode and sends a request to PCE every retry-timer seconds and up to the value of retry-count.
When the pce-report is enabled for the LSP and the FRR global revertive MBB is triggered following a bypass LSP activation by a PLR in the network, the PCC issues an updated PCRpt message with the new RRO reflecting the PLR and RRO hops. The PCE releases the bandwidth on the links that are no longer used by the LSP path.
If the user changes the RSVP-TE LSP configuration from pce-computation to no pce-computation, MBB procedures are not supported. In this case, the LSP path is torn down and is put into retry mode to compute a new path from the local CSPF on the router to signal the LSP.