Path Option; Reoptimization; Methods For Configuring Rsvp-Te Tunnels; Tracking Resources For Mpls Traffic Engineering - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

JUNOSe 11.1.x BGP and MPLS Configuration Guide
In this scenario, all the configured LSPs are up and active. If the LSP in use develops
problems and goes down, traffic is diverted to the LSP having the next best metric.

Path Option

You can configure multiple paths for an LSP with the tunnel mpls path-option
command. Each path option has an identifying number; the lower the number the
higher the preference for that path option. In this scenario, only a single LSP is up
and active at a time. If the path option currently in use by an LSP goes down, MPLS
tries to reroute the tunnel using the path option with the next highest preference. In
certain circumstances for example, when a tunnel is preempted by another MPLS
first attempts to reroute the tunnel with the current path option.

Reoptimization

You can use the traffic-engineering reoptimization capability to ensure that the best
path is being used. Suppose the current path goes down and MPLS switches to an
alternate path that is not as good as the failed path. You can have MPLS periodically
search according to a specified schedule for a path better than the alternate by
configuring the reoptimization timer. For example, you might configure MPLS to
search for a better path every 10 minutes; if it finds a better path, it switches.
On the other hand, you might be concerned about route flapping. If a path goes
down and then comes back up, perhaps it will continue to do so. In this case, you
might not ever want to go back to a path that goes down. To accomplish this, you
can configure reoptimization to never occur.
When you do not want the initial path to change that is, when you want to pin the
route you can disable reoptimization globally by setting the timer to 0. Alternatively,
you can disable reoptimization on a per-tunnel basis by using the lockdown option
with the tunnel mpls path-option command. LSP paths are always pinned until the
next reoptimization.
Finally, you can manually force an immediate reoptimization. See MPLS Global
Configuration Tasks in Configuring MPLS in the JUNOSe BGP and MPLS Configuration
Guide for information about configuring reoptimization.

Methods for Configuring RSVP-TE Tunnels

You can use either of the following methods to configure RSVP-TE tunnels:

Tracking Resources for MPLS Traffic Engineering

MPLS traffic engineering uses admission control to keep track of resource information.
Admission control has an accounting feature that ensures that requests are not
accepted when the router does not have sufficient resources to accommodate them.
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MPLS Traffic Engineering
Configure individual tunnels with the interface tunnel mpls: tunnelName
command.
Configure multiple tunnels with the same set of parameters with the mpls
tunnels profile command.