Spare capacity assignment in telecom networks using path restoration and further improvement using traffic splitting

Link restoration and path restoration are the two major techniques used for telecom network restoration in DCS (Digital Cross-connect System) mesh net works. Upon any link failure, for rerouting to be possible, sufficient spar e capacity must exist in the links of the chosen alternate paths, Path rest oration results in lower additional cost compared to link restoration. Path restoration planning corresponds to the multi-commodity flow problem, whic h is computationally NP-hard. In this paper, we present the details of an a pproximation scheme for the path based restoration planning problem and com pare the performance of link and path restoration schemes. These schemes ha ve been incorporated into the network planning tool developed at Alcatel Ne twork Systems. Traffic splitting can be used to further reduce the additional cost. There are several methods of performing traffic splitting. We have chosen to stud y even-splitting and best-splitting methods. We have evaluated traffic spli tting techniques by enhancing the link and path restoration modules of the Restoration Network Planning Tool developed by Alcatel Network Systems. We have observed, through several experiments, that traffic splitting results in significant reduction in the spare capacity and the corresponding augmen tation cost. (C) 1999 Elsevier Science Inc. All rights reserved.