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Understanding the Behavior of Delegated Label-Switched Paths

You can delegate the management of a router-configured label-switched path (LSP) to the NorthStar Controller by configuring the LSP from the router to be externally controlled. Any router-controlled LSP on the PCC can be delegated to the NorthStar Controller.

When an LSP is externally controlled, the controller manages the following LSP attributes:

  • Bandwidth

  • Setup and Hold priorities

  • LSP metric

  • ERO

Any configuration changes to the preceding attributes performed from the router are overridden by the values configured from the controller. Changes made to these attributes from the PCC do not take effect as long as the LSP is externally controlled. Any configuration changes made from the PCC take effect only when the LSP becomes locally or router controlled.

In both standalone and high availability (HA) cluster configurations, whenever a PCEP session goes down on a PCC, all the LSPs that originated from that PCC are removed from NorthStar except those with design parameters saved in NorthStar Controller. Examples of LSPs with design parameters include:

  • PCE-initiated LSPs

  • PCC-delegated LSPs with LSP attributes such as path, that have been modified by NorthStar

The following sections provide additional information:

Behavior of Delegated LSPs That Are Returned to Local PCC Control

When an LSP is externally controlled, any attempt to change the configuration of the LSP from the PCC (except for auto-bandwidth parameters) results in the display of a warning message from the router CLI. For delegated LSPs, any parameters configured from the PCC take effect only after the LSP is returned to local (PCC) control. When the LSP is returned to local control, the PCEP report messages report the state to the NorthStar Controller. If the NorthStar Controller is not available when the PCC configuration is changed locally, but becomes available some time after the configuration changes are made, the LSP is delegated with the reports carrying the latest state. When an LSP is externally controlled, configuration changes to bandwidth, setup and hold priorities, LSP metric, and ERO are overridden by the controller. Any configuration changes to these attributes made from the PCC do not take effect as long as the LSP is externally controlled. Only after the LSP becomes locally or router controlled will any configuration changes made from the PCC take effect. Table 1 shows the LSP parameters that can and cannot be configured from the PCC.

Table 1: Behavior of LSP Configurations Initiated from PCC

Configuration Statement

Description

admin-down

Not applicable to packet LSP.

admin-group

Results in a make-before-break (MBB) operation. The new LSP is reported; the old LSP is reported with the R-bit set.

auto-bandwidth

PCC automatically adjusts bandwidth based on the traffic on the tunnel. Supported on Juniper Networks routers only.

bandwidth

Results in an MBB operation. The new LSP is reported; the old LSP is reported with the R-bit set.

bandwidth ct0

Results in an MBB operation. The new LSP is reported; the old LSP is reported with the R-bit set.

class-of-service

No change reported from PCE.

description

No change reported from PCE.

disable

LSP is deleted on the router. The PCRpt message is sent with R-bit.

entropy-label

No change reported from PCE.

fast-reroute

Results in detour path setup; the detours are not reported to the controller.

from

LSP name change results in a new LSP being signaled, and the old LSP is deleted. The new LSP is reported through PCRpt message with D-bit. The old LSP is removed.

install

The prefix is applied locally and is not reflected to the PCE.

metric

Results in an MBB operation. The new LSP is reported, and the old LSP is reported with the R-bit set.

name

LSP name change results in a new LSP being signaled, and the old LSP is deleted. The new LSP is reported through PCRpt message with D-bit. The old LSP is removed.

node-link-protection

No change is reported from PCE. The LSP is brought down and then brought back up again. This sequence does not use an MBB operation.

priority

Results in an MBB operation. The new LSP is reported; the old LSP is reported with the R-bit set.

standby

Implementation of stateful path protection draft along with association object.

to

LSP name change results in a new LSP being signaled, and the old LSP is deleted.

Modifying Attributes of Delegated LSPs on the NorthStar Controller

When an LSP is externally controlled, local path computation is disabled, and you can modify the following attributes for the delegated LSP from the NorthStar Controller:

  • priority—Modifying this attribute results in an MBB operation.

  • admin-group—Modifying this attribute results in an MBB operation.

  • ERO—Modifying this attribute results in an MBB operation. The new LSP state is reported, and the old state is deleted.

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