All MBB types are supported for PCE-computed LSP. The LSP
MBB procedures for a PCE-computed LSP (path-computation-method pce
enabled and pce-control disabled) are as follows.
-
PCC issues a PCReq for the same PLSP-ID and includes the updated
constraints in the metric, LSPA, and bandwidth objects.
-
If PCE successfully finds a path, it replies with a PCRep message
with the ERO.
-
If 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 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 object with the LSP identifiers TLVs 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, PCC also includes a second set of metric,
LSPA, and bandwidth objects with the P-flag set to convey to PCE the constraints
of the path.
-
If the PCE returns no path or the RSVP-TE signaling of the
returned path failed, 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, PCC issues an updated PCRpt message with the new RRO reflecting the PLR
and RRO hops. 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
path-computation-method pce to no
path-computation-method, then 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 it.