This document describes alternate mechanisms to perform some of the
MPLS-TP linear protection sub-functions defined in RFC 6378. It also defines
some additional mechanisms. The purpose of these mechanisms is to closely
model the behavior of linear protection seen in other transport networks.
This document also introduces capabilities and modes for linear protection.
A capability is an individual behavior, and a mode is a particular combination
of capabilities. Two modes are defined PSC mode and APS mode.
The document describes the behavior of the PSC protocol including
when all the capabilities of the APS mode are enabled. The document
describes priority logic and the protocol state machine.
The document updates RFC 6378 in that the capability advertisement
method defined here is an addition to that document.
Working Group Summary
This document has a rather long history. It is intended to match the
operational practices and methods that have been used by transport
network operators prior to the introduction of MPLS. When RFC 6378 was
progressed it was decided that backwards compatibility with deployed MPLS
networks was the priority.
Later the discussion on meeting the requirements from transport network
operators re-emerged and it was decided that the solution should be based
on RFC 6378. To that end RFC 6378 had to be slightly extended and
modified. There were 5 capabilities missing in RFC 6378, these were the
extensions. There were also cases where relative priority between different
actions need to be changed, these were the modifications.
The first approach were to write a single document for each capability (at the
time it was thought that the capabilities might be activated independently),
The discussion in the working group however converged on putting all the
capabilities in one document.
The first MPLS Review Team review and the discussion in the working clearly
indicated a wish to make the merged document a working group document, so
the chairs initiated a second MPLS Review Team review and took the
decision to make it a working group document without running the normal WG
adoption poll, instead evaluating the discussion on the mailing and their own
The document has, nevertheless been well discussed within the working group.
After that the document became a working group document there has been a
good and open discussion on the mailing.
It is the Shepherds opinion that the document is ready for publication.
An implementation poll has been sent to the working group mailing
list and the write-up will be updated if and when the information is available.
There are strong indications of vendor interest.
There is a long list of important reviewers, especially the MPLS Review Team
reviewers that contributed the arguments that resulted in the current document
structure and that also did a careful technical review.
Loa Andersson is the document shepherd
Adrian Farrel is the responsible AD