Nortel Networks Corporation

Alcatel Communications, Inc.

Peter B Beaulieu

Bruce D Miller

Michael W Fortuna

Pierre A Humblet

William Abraham

Michael Yip

Roland T Provencher

Larnie Rabinowitz

Raj Shanmugaraj

Steven Sherry

Douglass E Walker

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.

Method and system for path protection in a communications network

An apparatus comprising system memory and a cache memory maintain system coherency for data stored in a subset of memory elements utilizing software coherency control, while system coherency for all remaining memory elements is maintained utilizing hardware coherency control.

Method and apparatus for increasing data rates in a data network while maintaining system coherency

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Plaistow, NH, United States of America

Peter B Beaulieu