Cr-Lsp - 3Com MSR 50 Series Configuration Manual

1348 C 77: MPLS TE C
HAPTER

CR-LSP

ONFIGURATION
They are different in that CR-LDP establishes LSPs using TCP while RSVP-TE using
raw IP.
RSVP is a well-established technology in terms of its architecture, protocol
procedures and support to services; while CR-LDP is an emerging technology with
better scalability.
Both CR-LDP and RSVP-TE are supported on your device.
Forwarding packets
Packets are forwarded over established tunnels.
Unlike ordinary LSPs established based on routing information, CR-LSPs are
established based on criteria such as bandwidth, selected path, and QoS
parameters in addition to routing information.
The mechanism setting up and managing constraints is called constraint-based
routing (CR).
CR-LSP involves these concepts:
"Strict and loose explicit routes" on page 1348
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"Traffic characteristics" on page 1348
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"Preemption" on page 1348
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"Route pinning" on page 1349
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"Administrative group and affinity attribute" on page 1349
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"Reoptimization" on page 1349
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Strict and loose explicit routes
An LSP is called a strict explicit route if all LSRs along the LSP are specified.
An LSP is called a loose explicit route if the downstream LSR selection conditions
rather than LSRs are defined.
Traffic characteristics
Traffic is described in terms of peak rate, committed rate, and service granularity.
The peak and committed rates describe the bandwidth constraints of a path while
the service granularity specifies a constraint on the delay variation that the CR-LDP
MPLS domain may introduce to a path's traffic.
Preemption
CR-LDP signals the resources required by a path on each hop of the route. If a
route with sufficient resources cannot be found, existing paths may be rerouted to
reallocate resources to the new path. This is called path preemption.
Two priorities, setup priority and holding priority, are assigned to paths for making
preemption decision. Both setup and holding priorities range from 0 to 7, with a
lower numerical number indicating a higher priority.