MPLS and RSVP-TE
100
MPLS Guide
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The following steps are for an LSP with an active path.
• If the user enabled the pce-computation option on a PCC-controlled LSP that
has an active path, no action is performed until the next time the router needs a
path for the LSP following a network event or an LSP parameter change. At that
point, the procedures above are followed.
• If the user enabled the pce-control option on a PCC-controlled or PCE-
computed LSP that has an active path, the PCC will issue a PCRpt message to
the PCE with the Up state and the RRO of the active path. The PCC will set the
delegation control flag to delegate control to the PCE. The PCE will keep the
active path of the LSP and will not update until the next network event or
reoptimization. At that point, the procedures above are followed.
The PCE supports the computation of disjoint paths for two different LSPs originating
or terminating on the same or different PE routers. To indicate this constraint to the
PCE, the user must configure the PCE path profile ID and path group ID that the LSP
belongs to. These parameters are passed transparently by the PCC to the PCE and
are therefore opaque data to the router. The user can configure the path profile and
path group using the path-profile profile-id [path-group group-id] command.
The association of the optional path group ID is to allow the PCE to determine which
profile ID this path group ID must be used with. One path group ID is allowed per
profile ID. The user can, however, enter the same path group ID with multiple profile
IDs by executing this command multiple times. A maximum of five entries of path-
profile [path-group] can be associated with the same LSP. More details of the
operation of the PCE path profile are provided in the PCEP chapter.
3.12.3 SR-TE LSP Path Computation
For PCC-controlled SR-TE LSPs, CSPF is not supported on the router. Whether the
cspf option is enabled or disabled for an SR-TE LSP, MPLS makes a request to the
TE-DB to get the label corresponding to each hop entered by the user in the primary
path of the SR-TE LSP. See PCC-initiated and PCC-controlled LSPs for details of
the hop-to-label translation.
The user can configure the path computation request of a CSPF-enabled SR-TE LSP
to be forwarded to a PCE instead of the local router CSPF by enabling the
pce-computation option, as explained in SR-TE LSP Instantiation. The user can
further delegate the reoptimization of the LSP to the PCE by enabling the pce-
control option. In both cases, the PCE is responsible for determining the label
required for each returned explicit hop and includes this in the SR-ERO.
In all cases, the user can configure the maximum number of labels that the ingress
LER can push for a particular SR-TE LSP by using the max-sr-labels command.
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