Collector rings are an integral part of typical metropolitan area networks and transport voice and data traffic from "collector nodes" (COs, End Offices) to the "collector hub" (e.g., POP, Tandem), where the traffic is either terminated or transferred to the long-haul network. The traffic is point-to-point TDM/SONET circuit. To assure "carrier grade" reliability, the collector networks are entirely based on SONET ring technology; each ring must pass through the collector hub. This paper addresses a topological design problem arising in planning and engineering of collector networks. Namely, given the traffic pattern and ring capacity, decide: (a) the number of the rings needed, (b) the ring connectivity and (c) the routing of the demands within the rings. The objective is to minimize the cost of the entire design subject to all demands being assigned. The problem is formulated as a large scale Integer Programming problem, and an LP relaxation based heuristic solution is developed. The heuristic is tested on sample problems.
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