MPLS Guide PCEP
3HE 18686 AAAB TQZZA © 2022 Nokia.
Use subject to Terms available at: www.nokia.com
319
• The PCE implementation supports the Segment-ID (SID) Depth value in the
METRIC object. This is always signaled by the PCC in the PCEP Open object
as part of the SR-PCE-CAPABILITY TLV. It is referred to as the Maximum Stack
Depth (MSD). In addition, the per-LSP value for the max-sr-labels option, if
configured, is signaled by the PCC to the PCE in the SID Depth value in a
METRIC object for both a PCE-computed LSP and a PCE-controlled LSP. The
PCE will compute and provide the full explicit path with TE links specified. If
there is no path with the number of hops lower than the MSD value or the SID
Depth value (if signaled), a reply with no path will be returned to the PCC.
• For a PCC-controlled LSP, if the label stack returned by the TE-DB hop-to-label
translation exceeds the per-LSP maximum SR label stack size, the LSP is
brought down.
• If the Path Setup Type (PST) TLV is not included in the PCReq message, the
PCE or PCC must assume it is for an RSVP-TE LSP.
Table 34 describes the segment routing extension objects and TLVs supported on
the 7705 SAR.
Note:
1. Nokia proprietary
4.4.4 LSP Initiation
An LSP that is configured on the router is referred to as a PCC-initiated LSP. An LSP
that is not configured on the router, but is instead created by the PCE at the request
of an application or a service instantiation, is referred to as a PCE-initiated LSP.
Table 34 PCEP Segment Routing Extension Objects and TLVs
TLV, Object, or Message Contained in Object Contained in Message
SR PCE CAPABILITY TLV OPEN OPEN
Path Setup Type (PST) TLV SRP
PCReq, PCRep, PCRpt
1
SR-ERO sub-object ERO
PCRep, PCRpt
1
SR-RRO sub-object RRO
PCReq, PCRpt
1
Segment-ID (SID) Depth
Value in METRIC object
METRIC
PCReq, PCRpt
1
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