MPLS model simulation

General information

An LSP path is a binding of an LSP to a provisioned path. An LSP path is either primary or secondary within the context of the parent LSP. The CPAM MPLS simulation model allows you to configure, monitor, and investigate the impact of the creation and removal of LSP configurations, in addition to the interaction between several LSPs.

The MPLS simulation allows you to determine which LSPs are impacted by topology changes—such as changes to metrics, operational state, bandwidth, or administrative groups—and to determine how different LSPs with conflicting bandwidth requirements interact. You can also configure changes to the measured bandwidth of individual LSPs, to see the impact on link utilization. The simulated MPLS model maintains a history of the actual path of the LSP.

When you create an MPLS scenario, you can import NFM-P dynamic LSPs and their primary and secondary LSP paths. In addition, simulated LSPs in one scenario can be imported into another scenario. You cannot import CPAM LSP path monitors into an MPLS scenario.

You can assign a processing order to each LSP in the simulation. The CPAM first processes the LSPs with a lower processing order. LSPs with equal processing orders are handled one at a time in a non-deterministic order. For example, the following LSPs are configured in the network with the assigned processing priority:

LSP A (processing order 1)
LSP B (processing order 2)
LSP C (processing order 2)

The simulator first processes LSP A. If LSP A results in any bandwidth reservations, the bandwidth reservations are recorded. Next, the simulator processes either LSP B or C.

Point-to-point LSP

The CPAM LSP is a simulation of the NFM-P LSP. The LSP has a single primary LSP path and multiple secondary LSP paths. Secondary paths may be standby paths. The simulated LSP allows you to monitor the active path of the LSP, to determine whether a primary or secondary path is used, or to determine whether a non-standby path should be made active. A history of the active paths is stored. You can highlight any historical active path on a topology map.

LSP paths

An LSP path represents a single simulated provisioned path contained within an LSP. The provisioned path, like the real LSP paths, has zero or more configured loose or strict hops. Historical path results are stored for the LSP path. You can highlight any historical actual path or potential actual path, or the provisioned path on a topology map.

When the simulated IGP topology is converged, you can perform a resignalling of the LSP so that the CPAM rebuilds the LSP path.

The following is the active path selection process:

Primary path is used.
If the primary path cannot be setup or is preempted, an operationally enabled secondary standby path is used.
If there is no operationally enabled secondary standby paths, an attempt is made to setup other secondary paths.
Each time we resignal and the active path is not the primary path, the simulator attempts to revert back to the primary path.

Non-constraint LSP path

An LSP path without CSPF enabled follows the normal IGP shortest path. If there is a topology change, the LSP path may be impacted and be rerouted (including optimization) or go down. The simulator evaluates during impact analysis, and immediately reroutes the LSP path, if necessary.

Importing paths into the simulation

When you create a scenario and start the simulator for the first time, and import the topology from the live network, you can import all or selected LSP paths and IP path monitors from the real network. The CPAM simulator imports the selected LSP paths and IP path monitors when the topology is imported.

For LSPs, the CPAM also imports the actual paths. If the CPAM cannot map a segment of the actual path to a simulator IGP link during the import, the segment is not imported.

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