PCEP
328
MPLS Guide
© 2022 Nokia.
Use subject to Terms available at: www.nokia.com
3HE 18686 AAAB TQZZA
4.5.3.1 PCC-Controlled LSPs
All MBB types are supported for PCC-controlled LSPs. The LSP MBB procedures for
a PCC-controlled LSP (pce-computation and pce-control disabled) are as follows.
1. MPLS submits a path request, including the updated path constraints, to the
local CSPF.
2. If the local CSPF 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 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.
3. If the CSPF 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 the local CSPF every
retry-timer seconds and up to the value of retry-count.
4. When 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.
4.5.3.2 PCE-Computed LSPs
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.
1. 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.
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