Cisco Cisco IOS Software Release 12.2(33)SRE
RSVP Fast Local Repair
Prerequisites for RSVP FLR
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Cisco IOS Release 12.2(33)SRB
Prerequisites for RSVP FLR
You must configure RSVP on one or more interfaces on at least two neighboring routers that share a link
within the network.
within the network.
Restrictions for RSVP FLR
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RSVP FLR applies only when RSVP is used to set up resource reservations for IPv4 unicast flows;
IPv4 multicast flows are not supported.
IPv4 multicast flows are not supported.
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RSVP FLR does not apply to traffic engineering (TE) tunnels and, therefore, does not affect TE
sessions.
sessions.
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RSVP FLR does not support message bundling.
Information About RSVP FLR
To use the RSVP FLR feature, you should understand the following concepts:
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Feature Overview of RSVP FLR
RSVP FLR provides for dynamic adaptation when routing changes occur. When a route changes, the
next PATH and RESV message refreshes establish path and reservation states along the new route.
Depending on the configured refresh interval, this reroute happens in tens of seconds. However, during
this time, the QoS of flows is not guaranteed because congestion may occur while data packets travel
over links where reservations are not yet in place.
next PATH and RESV message refreshes establish path and reservation states along the new route.
Depending on the configured refresh interval, this reroute happens in tens of seconds. However, during
this time, the QoS of flows is not guaranteed because congestion may occur while data packets travel
over links where reservations are not yet in place.
In order to provide faster adaptation to routing changes, without the overhead of a refresh period, RSVP
registers with the routing information base (RIB) and receives notifications when routes change, thereby
triggering state refreshes for the affected destinations. These triggered refreshes use the new route
information and, as a result, install reservations over the new path.
registers with the routing information base (RIB) and receives notifications when routes change, thereby
triggering state refreshes for the affected destinations. These triggered refreshes use the new route
information and, as a result, install reservations over the new path.
When routes change, RSVP has to reroute all affected paths and reservations. Without FLR, the reroute
happens when refresh timers expire for the path states. With real time applications such as VoIP and VoD,
the requirement changes and the reroute must happen quickly, within three seconds from the triggering
event such as link down or link up.
happens when refresh timers expire for the path states. With real time applications such as VoIP and VoD,
the requirement changes and the reroute must happen quickly, within three seconds from the triggering
event such as link down or link up.
illustrates the FLR process.