Configure the head-end router as PCEP Path Computation Client (PCC) to establish a connection to the PCE. The PCC and PCE
addresses must be routable so that TCP connection (to exchange PCEP messages) can be established between PCC and PCE.
Configure the PCC to Establish a Connection to the PCE
Use the segment-routing traffic-eng pcc command to configure the PCC source address, the SR-PCE address, and SR-PCE options.
A PCE can be given an optional precedence. If a PCC is connected to multiple PCEs, the PCC selects a PCE with the lowest precedence
value. If there is a tie, a PCE with the highest IP address is chosen for computing path. The precedence value range is from 0 to 255.
Router(config)# segment-routing
Router(config-sr)# traffic-eng
Router(config-sr-te)# pcc
Router(config-sr-te-pcc)# source-address ipv4 local-source-address
Router(config-sr-te-pcc)# pce address ipv4 PCE-address[precedence value]
Router(config-sr-te-pcc)# pce address ipv4 PCE-address[password {clear | encrypted} LINE]
Router(config-sr-te-pcc)# pce address ipv4 PCE-address[keychain WORD]
Configure PCEP-Related Timers
Use the timers keepalive command to specify how often keepalive messages are sent from PCC to its peers. The range is from 0 to 255 seconds; the default
value is 30.
Router(config-sr-te-pcc)# timers keepalive seconds
Use the timers deadtimer command to specify how long the remote peers wait before bringing down the PCEP session if no PCEP messages are received
from this PCC. The range is from 1 to 255 seconds; the default value is 120.
Router(config-sr-te-pcc)# timers deadtimer seconds
Use the timers delegation-timeout command to specify how long a delegated SR policy can remain up without an active connection to a PCE. The range is from
0 to 3600 seconds; the default value is 60.
Router(config-sr-te-pcc)# timers delegation-timeout seconds
PCE-Initiated SR Policy Timers
Use the timers initiated orphans command to specify the amount of time that a PCE-initiated SR policy will remain delegated to a PCE peer that is no longer
reachable by the PCC. The range is from 10 to 180 seconds; the default value is 180.
Router(config-sr-te-pcc)# timers initiated orphans seconds
Use the timers initiated state command to specify the amount of time that a PCE-initiated SR policy will remain programmed while not being delegated to
any PCE. The range is from 15 to 14440 seconds (24 hours); the default value is 600.
Router(config-sr-te-pcc)# timers initiated state seconds
To better understand how the PCE-initiated SR policy timers operate, consider the following example:
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PCE A instantiates SR policy P at head-end N.
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Head-end N delegates SR policy P to PCE A and programs it in forwarding.
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If head-end N detects that PCE A is no longer reachable, then head-end N starts the PCE-initiated orphan and state timers for SR policy P.
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If PCE A reconnects before the orphan timer expires, then SR policy P is automatically delegated back to its original PCE (PCE A).
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After the orphan timer expires, SR policy P will be eligible for delegation to any other surviving PCE(s).
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If SR policy P is not delegated to another PCE before the state timer expires, then head-end N will remove SR policy P from its forwarding.
Enable SR-TE SYSLOG Alarms
Use the logging policy status command to enable SR-TE related SYSLOG alarms.
Router(config-sr-te)# logging policy status
Enable PCEP Reports to SR-PCE
Use the report-all command to enable the PCC to report all SR policies in its database to the PCE.
Router(config-sr-te-pcc)# report-all
Customize MSD Value at PCC
Use the maximum-sid-depth
value command to customize the Maximum SID Depth (MSD) signaled by PCC during PCEP session establishment.
The default MSD value is equal to the maximum MSD supported by the platform (5).
Router(config-sr-te)# maximum-sid-depth value
Note
|
The platform's SR-TE label imposition capabilities are as follows:
|
For cases with path computation at PCE, a PCC can signal its MSD to the PCE in the following ways:
After path computation, the resulting label stack size is verified against the MSD requirement.
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If the label stack size is larger than the MSD and path computation is performed by PCE, then the PCE returns a "no path"
response to the PCC.
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If the label stack size is larger than the MSD and path computation is performed by PCC, then the PCC will not install the
path.
Note
|
A sub-optimal path (if one exists) that satisfies the MSD constraint could be computed in the following cases:
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For a dynamic path with TE metric, when the PCE is configured with the pce segment-routing te-latency command or the PCC is configured with the segment-routing traffic-eng te-latency command.
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For a dynamic path with LATENCY metric
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For a dynamic path with affinity constraints
For example, if the PCC MSD is 4 and the optimal path (with an accumulated metric of 100) requires 5 labels, but a sub-optimal
path exists (with accumulated metric of 110) requiring 4 labels, then the sub-optimal path is installed.
|
Customize the SR-TE Path Calculation
Use the te-latency command to enable ECMP-aware path computation for TE metric.
Router(config-sr-te)# te-latency
Note
|
ECMP-aware path computation is enabled by default for IGP and LATENCY metrics.
|
Configure PCEP Redundancy Type
Use the redundancy pcc-centric command to enable PCC-centric high-availability model, where the PCC allows only the PCE with the lowest precedence to initiate
policies.
Router(config-sr-te-pcc)# redundancy pcc-centric
Configuring Head-End Router as PCEP PCC and Customizing SR-TE Related Options: Example
The following example shows how to configure an SR-TE head-end router with the following functionality:
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Enable the SR-TE head-end router as a PCEP client (PCC) with 3 PCEP servers (PCE) with different precedence values. The PCE
with IP address 10.1.1.57 is selected as BEST.
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Enable SR-TE related syslogs.
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Set the Maximum SID Depth (MSD) signaled during PCEP session establishment to 5.
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Enable PCEP reporting for all policies in the node.
segment-routing
traffic-eng
pcc
source-address ipv4 10.1.1.2
pce address ipv4 10.1.1.57
precedence 150
password clear <password>
!
pce address ipv4 10.1.1.58
precedence 200
password clear <password>
!
pce address ipv4 10.1.1.59
precedence 250
password clear <password>
!
!
logging
policy status
!
maximum-sid-depth 5
pcc
report-all
!
!
!
end
Verification
RP/0/RSP0/CPU0:Router# show segment-routing traffic-eng pcc ipv4 peer
PCC's peer database:
--------------------
Peer address: 10.1.1.57, Precedence: 150, (best PCE)
State up
Capabilities: Stateful, Update, Segment-Routing, Instantiation
Peer address: 10.1.1.58, Precedence: 200
State up
Capabilities: Stateful, Update, Segment-Routing, Instantiation
Peer address: 10.1.1.59, Precedence: 250
State up
Capabilities: Stateful, Update, Segment-Routing, Instantiation
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