Technical Summary
This document defines extensions to and describes the use of RSVP to
establish backup label-switched path (LSP) tunnels for local repair
of LSP tunnels. These mechanisms enable the re-direction of traffic
onto backup LSP tunnels in 10s of milliseconds in the event of a
failure. Two methods are defined. The one-to-one backup method creates
detour LSPs for each protected LSP at each potential point of local
repair. The facility backup method creates a bypass tunnel to
protect a potential failure point; by taking advantage of MPLS label
stacking, this bypass tunnel can protect a set of protected LSPs that
have similar backup constraints. Both methods can be used to protect
links and nodes during network failure. The described behavior and
extensions to RSVP allow nodes to implement either or both methods
and to interoperate in a mixed network.
Working Group Summary
Several years before work began on this draft, operational networks
had deployed two independent methods of doing fast reroute, called
herein one-to-one backup and facility backup. Vendors trying to
support both methods were experiencing incompatiblity problems in
attempting to produce a single implementation capable of
interoperating with both. There are technical tradeoffs between
the methods. However these tradeoffs are so topologically
dependent, that the community has not converged on a single
approach. Both methods are considered necessary to cover different
topological scenarios.
Protocol Quality
The specification has been reviewed for the IESG by Alex Zinin.