CR-LDP: Constraint-based Label Distribution Protocol Overview


CR-LDP: Constraint-based Label Distribution Protocol Overview
CR-LDP, constraint-based LDP, is one of the protocols in the MPLS architecture. CR-LDP contains extensions for LDP to extend its capabilities such as setup paths beyond what is available for the routing protocol. For instance, an LSP can be setup based on explicit route constraints, QoS constraints, and other constraints. Constraint-based routing (CR) is a mechanism used to meet Traffic Engineering requirements. These requirements are met by extending LDP for support of constraint-based routed label switched paths (CR-LSPs). Other uses for CR-LSPs include MPLS-based VPNs.


Protocol Structure - CR-LDP Constraint-based Label Distribution
CR-LDP has the same structure as 
LDP except the following additional TLV parameters. 
Value
Parameter
821
LSPID
822
ResCls
503
Optical Session Parameters
800
Explicit Route
801-804
ER-Hop TLVS
810
Traffic Parameters
820
Preemption
823
Route Pinning
910
Optical Interface Type
920
Optical Trail Desc
930
Optical Label
940
Lambada Set
CR-LDP is defined by IETF (http://www.ietf.org ) RFC3212.

Reference
http://www.javvin.com/protocol/rfc3031.pdf £ºMultiprotocol Label Switching Architecture
http://www.javvin.com/protocol/rfc3212.pdf £ºCR-LDP Specification

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