Optimal Spare Capacity Preconfiguration for Faster Restoration of Mesh Networks [Vol. 5, No. 2, 1997]

Optimal Spare Capacity Preconfiguration for Faster Restoration of Mesh Networks

M.H. MacGregor
TRLabs and University of Alberta
Department of Electrical and Computer Engineering
Edmonton, T6G 2E1, Canada

W.D. Grover
800 Park Plaza
10611-98 Ave. Edmonton
Alberta, Canada T5K 2P7
Email: grover_AT_edm.trlabs.ca

K. Ryhorchuk
TRLabs and University of Alberta
Department of Electrical and Computer Engineering
Edmonton, T6G 2E1, Canada

Abstract
Several distributed real-time methods have been proposed for restoration from single span failures in digital transport networks. These methods have the potential to avoid user service outages due to such failures, if they operate quickly enough. For example, switched 64 kbps connections will not be disconnected if the network can be restored before the time at which calls in progress are dropped, typically 1-2 seconds after a failure. However, it will be difficult to achieve the goal of sub-second restoration if cross-connects cannot operate crosspoint quickly enough, either due to large workloads during a restoration response, or because of implementation choices such as testing each cross-connection while in the midst of a serious outage. The results in this paper demonstrate that it can be useful to pre-operate selected cross-points between the spare links of a mesh-restorable network before any failure has occurred, putting the network into a statistically optimal state of readiness. When a failure occurs, some of the preconfigured restoration path bundles can be used immediately. If more restoration paths are needed, they can be obtained by a real-time restoration process. The first advantage of preconfiguration is that the number of cross-connection operations may be greatly reduced or eliminated for a portion of the affected traffic. This will reduce restoration time significantly. Secondly, after utilizing preconfigured restoration paths, the workload of a real-time restoration process will be lower because it will be searching for fewer paths. This paper demonstrates that preconfiguration can supply a significant proportion of the replacement capacity required after a span failure. The results are obtained through integer programming.

Keywords: Telecommunications; restoration; cross-connect.

JNSM: Vol. 5, No. 2, 1997 Optimal Spare Capacity Preconfiguration for Faster Restoration of Mesh Networks [Vol. 5, No. 2, 1997]

NOTE: only abstract of paper available on-line

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