Beta Draft Confidential
21-201/19/05 ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Configuring PNNI Routing
PNNI Reroute Load Balancing
PNNI Reroute Load Balancing
This section describes the PNNI Reroute Load Balancing feature. This feature
automatically reroutes active PVCs and SPVCs within the PNNI routing domain to
lower cost paths as they become available. In addition, this feature also provides
graceful recovery when PNNI link connections or modules go out of service (due to
upgrades, reboots, or network failures).
When a PNNI link returns to service following a network disruption, Reroute Load
Balancing gradually reroutes circuits over their original path without requiring manual
intervention. This feature also operates when new paths are established in the network,
distributing circuits on a controlled basis to newly available links. By pacing circuit
reroutes, Reroute Load Balancing prevents congestion on PNNI links and promotes
efficient reuse of network resources.
PNNI Reroute Load Balancing Criteria
PNNI Reroute Load Balancing periodically examines active circuits in round-robin
order to determine whether a better path through the PNNI routing domain is
available. If a better path is detected, the circuit is first cleared over the original path
and then re-established over the new path.
When a PNNI route returns to service, Reroute Load Balancing reroutes circuits back
to their original path using the following criteria:
• When both the original and alternate PNNI routes are similar in cost, no reroute
load balancing occurs and neither circuit is rerouted.
• When the original PNNI route offers a cost advantage, all circuits are rerouted
back to this path.
• Reroute Load Balancing is performed according to the configured values for the
Reroute Count and Reroute Delay parameters. See “Defining Reroute Tuning” on
page 21-21 for more information.
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