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:
•
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.
Related Topics See Configuring MPLS on page 275, for information about displaying information related
to traffic-engineering resources
•
Tracking Resources for MPLS Traffic Engineering Overview
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.
Currently, bandwidth (BW) and bandwidth-related information are the only resources
tracked and used for traffic engineering. Admission control determines whether a setup
request can be honored for an MPLS LSP with traffic parameters.
Admission control provides bandwidth information to the IGP protocols, ISIS and OSPF.
As new LSPs are created, the available bandwidth decreases. The IGPs can subsequently
advertise this information and use it for SPF calculations to determine paths that satisfy
the traffic requirements. You can configure readvertisement to occur periodically or when
the change crosses some threshold.
253Copyright © 2010, Juniper Networks, Inc.
Chapter 3: MPLS Overview
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