TOPOLOGICAL NETWORK DESIGN FOR SONET RING ARCHITECTURE

Service restoration and survivability have become increasingly importa nt in telecommunications network planning with the introduction of fib er optic, high speed networks, Recent technological advances, such as synchronous optical network (SONET) technology, promotes the use of in terconnected rings in designing reliable networks. We describe a heuri stic approach for designing networks comprised of interconnected rings , Our approach is particularly attractive for relatively sparse networ ks in which the set of all cycles (constituting the potential rings) c an be determined at a reasonable computational effort. Most telecommun ications networks would fall into this category. Given a set of nodes, with demand among all possible node-pairs, and a set of available lin ks that connect the nodes (e.g., existing fiber links), the problem is to select an optimal subset of rings, utilizing only allowable links, such that each node is included in at least one ring and each ring is connected to at least one other ring at two or more nodes, Such a mul tiple ring network will ensure instantaneous restoration of service in case of a single link or single node failure. In our solution approac h, we first generate a large set of candidate rings and approximate th e cost of each ring based on the nodes that are served by the ring and based on the demands. We then apply a set covering algorithm that sel ects a (minimum cost) subset of the candidate rings such that each nod e is included on at least one ring. Finally, we select a few additiona l rings in order to achieve the required connectivity among the rings. me present computational results for realistic-size (e.g., 500 nodes) telecommunication networks.