Make-Before-Break (MBB) Procedures for LSP/Path Parameter Configuration Change

When an LSP is switched from an existing working path to a new path, it is desirable to perform this in a hitless fashion. The Make-Before-Break (MBB) procedure consist of first signaling the new path when it is up, and having the ingress LER move the traffic to the new path. Only then the ingress LER tears down the original path.

MBB procedure is invoked during the following operations:

  1. Timer based and manual resignal of an LSP path.

  2. Fast-ReRoute (FRR) global revertive procedures.

  3. Soft Pre-emption of an LSP path.

  4. Traffic-Engineering (TE) graceful shutdown procedures.

  5. Update of secondary path because of an update to primary path SRLG.

  6. LSP primary or secondary path name change.

  7. LSP or path configuration parameter change.

In a prior implementation, item7 covers the following parameters:

  1. Changing the primary or secondary path bandwidth parameter on the fly.

  2. Enabling the frr option for an LSP.

This feature extends the coverage of the MBB procedure to most of the other LSP level and Path level parameters as follows:

  1. Changes to include/exclude of admin groups at LSP and path levels.

    Enabling/disabling LSP level path-computation local-cspf option.

  2. Enabling/disabling LSP level metric-type parameter.

  3. Enabling/disabling LSP level propagate-admin-group option.

  4. Enabling/disabling LSP level hop-limit option in the fast-reroute context.

  5. Enabling the LSP level least-fill option.

  6. Enabling/disabling LSP level adspec option.

  7. Changing between node-protect and ‟no node-protect” (link-protect) values in the LSP level fast-reroute option.

  8. Changing LSP primary or secondary path priority values (setup-priority and hold-priority).

  9. Changing LSP primary or secondary path class-type value and primary path backup-class-type value.

  10. Changing LSP level and path level hop-limit parameter value.

  11. Enabling/disabling primary or secondary path record and record-label options.

This feature is not supported on a manual bypass LSP.

P2MP Tree Level Make-before-break operation is supported if changes are made to the following parameters on LSP-Template:

Parent topic: Advanced MPLS/RSVP Features