PCE-controlled LSPs

About this task

The LSP MBB procedures for a PCE-controlled LSP (pce-control enabled) are as follows.

Items 1 through 5 of the following procedures apply to the Config Change, Manual Resignal, and Auto-Bandwidth MBB types. The Delayed Retry MBB type used with the SRLG on secondary standby LSP feature is not supported with a PCE controlled LSP. See Behavior of secondary LSP paths for information about the SRLG on secondary standby LSP feature.

Procedure

The PCC temporarily removes the delegation by sending a PCRpt message for the corresponding PLSP-ID with the delegation D-bit clear.
For an LSP with path-computation-method disabled, MPLS submits a path request to the local CSPF including the updated path constraints.
For an LSP with path-computation-method pce enabled, PCC issues a PCReq message for the same PLSP-ID and includes the updated constraints in the metric, LSPA, or BANDWIDTH objects.
The BANDWIDTH object contains the current operational bandwidth of the LSP in the case of the auto-bandwidth MBB.
- 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 local CSPF or the PCE return a path, the PCC performs the following actions.
1. The PCC signals the LSP with the RSVP control plane and moves traffic to the new MBB path. It then sends a PCRpt message with the delegation D-bit set to return delegation and containing the RRO and LSP object, 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 disabled the report-path-constraints option under the pcc context, the PCC also includes a second set of metric, LSPA, or BANDWIDTH objects with the P-flag set to convey the constraints of the path to the PCE.
2. The PCC sends a PathTear message to delete the state of the older path in the network. The PCC then sends a PCRpt message to the PCE with the older path PLSP-ID and the remove R-bit set to also have PCE remove the state of that LSP from its database.
If the local CSPF or the PCE returns no path or the RSVP-TE signaling of the returned path fails, the router makes no further requests. That is, there is no retry for the MBB.
1. The PCC sends a PCErr message to the PCE with the LSP error code field of the LSP-ERROR-CODE TLV set to a value of 8 (RSVP signaling error) if the MBB failed because of an RSVP-TE signaling error.
2. The PCC sends a PCRpt message with the delegation D-bit set to return delegation and containing the RRO and LSP objects with the LSP identifiers TLV containing the LSP-ID of the currently active path. The message includes the metric, LSPA, and BANDWIDTH objects with the P-flag is clear to indicate the operational values of these parameters. Unless the user disabled 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 the constraints of the path to the PCE.
The ingress LER takes no action in the case of a network event triggered MBB, such as FRR Global Revertive, TE Graceful Shutdown, or Soft Pre-Emption.
1. The ingress PE keeps the information as required and sets the state of the MBB to one of the FRR Global Revertive, TE Graceful Shutdown, or Soft Pre-emption MBB values but does not perform the MBB action.
2. The NRC-P computes a new path in the case of Global Revertive MBB because of a failure event. This computation uses the PCUpd message to update the path using the MBB procedure described in Behavior of the LSP path update. The activation of a bypass LSP by a PLR in the network causes the PCC to issue 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.
3. The NRC-P computes a new path in the case of the TE graceful MBB if the RSVP-TE is using the TE metric, because the TE metric of the link in the TE graceful shutdown is set to infinity. This computation uses the PCUpd message to update the path using the MBB procedure described in Behavior of the LSP path update.
4. The NRC-P does not act on the TE graceful MBB if the RSVP-TE is using the IGP metric or is on the soft pre-emption MBB; however, the user can perform a manual resignal of the LSP path from the NRC-P to force a new path computation, which accounts for the newly available bandwidth on the link that caused the MBB event. This computation uses the PCUpd message to update the path using the MBB procedure. See Behavior of the LSP path update for more information about the MBB procedure.
5. The user can perform a manual resignal of the LSP path from the ingress LER, which forces an MBB for the path as described in the remove-delegation, MBB, and return-delegation procedures described in this section.
6. If the user performs no pce-control while the LSP still has the state for any of the network event triggered MBBs, the MBB is performed immediately by the PCC as described in the procedures in PCE-computed LSPs for a PCE-computed LSP and as described in the procedures in PCC-controlled LSPs for a PCC-controlled LSP.
The timer-based resignal MBB behaves like the TE graceful or soft pre-emption MBB. The user can perform a manual resignal of the LSP path from the ingress LER or from PCE.
The Path Update MBB (tools perform router mpls update-path) is failed and results in a no operation. This is true in all cases when the RSVP-TE LSP enables the pce-report option.