Shared mesh protection allows a set of diversely routed paths with
diverse endpoints to collectively oversubcribe protection resources.
Under normal conditions no single failure will result in the capacity
of the associated protection resources to be exhausted.
When multiple failures occur such that more than one path in the set
of paths utilizing shared protection resources is affected, the
necessity arises of pre-empting traffic on the basis of business
priority rather than application priority.
This memo describes the use of SPMEs and TC marking as a means of
indicating business priority for shared mesh protection.