Dynamic CRLSP establishment

Dynamic CRLSPs are dynamically established through a label distribution protocol (such as RSVP-TE). The label distribution protocol advertises labels to establish CRLSPs and reserves bandwidth resources on each node along the calculated path.

Dynamic CRLSPs adapt to network changes and support CRLSP backup and fast reroute, but they require complicated configurations.

The device supports the label distribution protocol of RSVP-TE for MPLS TE. Resource Reservation Protocol (RSVP) reserves resources on each node along a path. Extended RSVP can support MPLS label distribution and allow resource reservation information to be transmitted with label bindings. This extended RSVP is called RSVP-TE.

For more information about RSVP, see "Configuring RSVP."

TE constraints include the affinity and explicit path. They are configured on the ingress node of an MPLS TE tunnel.

• Affinity

  Affinity determines which links a tunnel can use. The affinity attribute and its mask, and the link attribute are all 32-bit long. A link is available for a tunnel if the link attribute meets the following requirements:

  • The link attribute bits corresponding to the affinity attribute's 1 bits whose mask bits are 1 must have at least one bit set to 1.

  • The link attribute bits corresponding to the affinity attribute's 0 bits whose mask bits are 1 must have no bit set to 1.

  The link attribute bits corresponding to the 0 bits in the affinity mask are not checked.

  For example, if the affinity attribute is 0xFFFFFFF0 and its mask is 0x0000FFFF, a link is available for the tunnel when its link attribute bits meet the following requirements: the highest 16 bits each can be 0 or 1 (no requirements), the 17^th through 28^th bits must have at least one bit whose value is 1, and the lowest four bits must be 0.

• Explicit path

  Explicit path specifies the nodes to pass and the nodes to not pass for a tunnel.

  Explicit paths include the following types:

  • Strict explicit path—Among the nodes that the path must traverse, a node and its previous hop must be connected directly.

  • Loose explicit path—Among the nodes that the path must traverse, a node and its previous hop can be connected indirectly.

  Strict explicit path precisely specifies the path that an MPLS TE tunnel must traverse. Loose explicit path vaguely specifies the path that an MPLS TE tunnel must traverse. Strict explicit path and loose explicit path can be used together to specify that some nodes are directly connected and some nodes have other nodes in between.