The Make-Before-Break (MBB) procedure allows an LSP to switch from an existing working path to a new path without interrupting service. The MBB procedure does this by first signaling the new path when it is operationally up, having the ingress LER move the traffic to the new path, and then allowing the ingress LER to tear down the original path.
The MBB procedure is invoked during the following operations:
timer-based and manual resignal of an LSP path
Fast Reroute (FRR) global revertive procedures
Traffic Engineering (TE) graceful shutdown procedures
update of the secondary path due to an update to the primary path SRLG
LSP primary or secondary path name change
LSP or path configuration parameter change
MBB procedure coverage has been extended to most of the other LSP-level and path-level parameters as follows:
including or excluding admin groups at the LSP and path levels
enabling or disabling the LSP-level CSPF option
enabling or disabling LSP-level use-te-metric parameters when the CSPF option is enabled
enabling or disabling the LSP-level hop-limit option in the fast-reroute context
enabling the LSP-level least-fill option
enabling or disabling the LSP-level adspec option
changing between node-protect and no node-protect (link-protect) values in the LSP-level fast-reroute option
changing the LSP-level and path-level hop-limit parameter values
enabling or disabling primary or secondary path record or record-label options
The MBB procedure is not supported on a manual bypass LSP.