A system and method for fast and reliable failure notification and accelerated
switchover for path protection in a communications network having several overlapping
areas of nodes interconnected by communications links is described. Upon a failure
event involving one of the communications links, a failure message is broadcast
identifying the failed link, the broadcast being confined within the areas which
include the failed link. A reliable transmission protocol is provided wherein at
one or more of the nodes, a LAPD protocol unnumbered information frame containing
the failure message is sent to connected nodes. The failure message is resent in
another unnumbered information frame after a time interval unless an unnumbered
acknowledgment frame containing or referencing the failure message is received
from the connected node. A method of path protection includes establishing plural
working paths through the nodes. For each working path, an associated protection
path is precalculated. A priority is assigned to each working path and associated
protection path. A protection path is precalculated for each area through which
a particular working path traverses. Upon a failure event, working paths that include
the failed link are switched to their respective protection paths. Higher priority
protection paths can preempt lower priority paths that share at least one link.
At each node, linked lists for protection path activation, working path deactivation
and path preemption are implemented upon a failure event.