MPLS Guide PCEP
3HE 18686 AAAB TQZZA © 2022 Nokia.
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4.5.2.1 Path Update with Empty ERO
When the NRC-P reoptimizes the path of a PCE-controlled RSVP-TE LSP, it is
possible that a path that satisfies the constraints of the LSP no longer exists. In this
case, the NRC-P sends a PCUpd message with an empty ERO, which forces the
PCC to bring down the path of the RSVP-TE LSP.
The NRC-P sends a PCUpd message with an empty ERO if any of the following
cases are true:
• the requested bandwidth is the same as the current bandwidth, which avoids
bringing down the path due to a resignal during an MBB transition
• local protection is not currently in use, which avoids bringing down a path that
activated an FRR backup path. The LSP can remain on the FRR backup path
until a new primary path can be found by the NRC-P.
• the links of the current path are all operationally up, which allows the NRC-P to
ensure that the RSVP control plane will report the path down when a link is down
and not prematurely bring the path down with an empty ERO
4.5.3 Behavior of LSP MBB
In addition to the MBB support when the PCC receives a path update, as described
in Behavior of the LSP Path Update, an RSVP-TE LSP supports the MBB procedure
for any parameter configuration change, including the PCEP-related commands
when they result in a change to the path of the LSP.
If the user adds or modifies the path-profile command for an RSVP-TE LSP, a
config change MBB is only performed if the pce-computation, pce-report, or
pce-control options are enabled on the LSP. Otherwise, no action occurs. When
pce-computation, pce-report, or pce-control are enabled on the LSP, the path
update MBB (tools>perform>router>mpls>update-path) fails, resulting in no
operation.
MBB is also supported for the manual resignal and auto-bandwidth MBB types.
When the LSP goes into an MBB state at the ingress LER, the behavior is dependent
on the operating mode of the LSP.
This section contains information on the following LSP MBB procedures:
• PCC-Controlled LSPs
• PCE-Computed LSPs
• PCE-Controlled LSPs
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