MPLS and RSVP-TE
92
MPLS Guide
© 2022 Nokia.
Use subject to Terms available at: www.nokia.com
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A PCC-initiated and PCE-controlled SR-TE LSP allows active stateful mode,
which enables the pce-control option for the SR-TE LSP so that the PCE can
perform path computation and updates following a network event without the
explicit request from the PCC. The PCC delegates full control.
The user can configure the path computation requests only (PCE-computed) or both
path computation requests and path updates (PCE-controlled) to the PCE for a
specific LSP using the pce-computation and pce-control commands.
The pce-computation option sends the path computation request to the PCE
instead of the local CSPF. When this option is enabled, the PCE acts in passive
stateful mode for this LSP. In other words, the PCE can perform path computations
for the LSP only at the request of the router. This is used in cases where the operator
wants to use the PCE specific path computation algorithm instead of the local router
CSPF algorithm.
The default value is no pce-computation. Enabling pce-computation requires that
the cspf option also be enabled; otherwise, the command is rejected. If the cspf
option is disabled for an LSP, the pce-computation option will also be automatically
disabled.
Enabling cspf without enabling pce-computation for an SR-TE LSP means that,
internally, the router still performs label translation as if cspf was disabled, because
there is no support of CSPF for an SR-TE LSP on the router.
The pce-control option allows the router to delegate full control of the LSP to the
PCE (PCE-controlled). Enabling this option means that the PCE is acting in active
stateful mode for this LSP and the PCE can reroute the path following a failure or to
reoptimize the path and update the router without requiring a request from the router.
In all cases, the PCC LSP database is synchronized with the PCE LSP database
using the PCEP path computation state report (PCRpt) message for LSPs that have
the pce-report command enabled.
Note:
• The user can delegate CSPF and non-CSPF LSPs.
• The user can delegate LSPs that have the pce-computation option enabled or
disabled. The LSP maintains its latest active path computed by the PCE or the router
at the time it was delegated. The PCE will only make an update to the path at the next
network event or reoptimization. The default value is no pce-control.
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