Configuring Isolated LSP Computation

Most IP radio access networks (IP RANs) that use Multiprotocol Label Switching (MPLS) TE have high reliability requirements for LSPs. However, the existing CSPF algorithm simplifies the LSP path according to the principle of minimizing the link cost, and cannot automatically calculate the completely separate primary and secondary LSP paths.

Specifying explicit paths can meet this reliability requirement; this method, however, does not adapt to topology changes. Each time a node is added to or deleted from the IP RAN, carriers must modify the explicit paths, which is time-consuming and laborious.

To resolve these problems, you can configure isolated LSP computation. After this feature is enabled, the disjoint and CSPF algorithms work together to compute primary and hot-standby LSPs at the same time and cut off crossover paths of the two LSPs. Then, the device gets the isolated primary and hot-standby LSPs.

• Isolated LSP computation is a best-effort technique. If the disjoint and CSPF algorithms cannot get isolated primary and hot-standby LSPs or two isolated LSPs do not exist, the device uses the primary and hot-standby LSPs computed by CSPF.

• After you enable the disjoint algorithm, the shared risk link group (SRLG), if configured, becomes ineffective.

Pre-configuration Tasks

Before configuring isolated LSP computation, complete the following tasks:

• Configure an RSVP-TE tunnel.

• Configure CR-LSP backup and establish a hot-standby CR-LSP.

• CSPF must be enabled on ingress node of the RSVP-TE tunnel.

• Isolated LSP computation requires the collaboration of the CR-LSP hot standby feature and requires the hot-standby LSP to have the same reserved bandwidth as the primary LSP.