On Provisioning in Dual-Node Interconnected SONET/SDH Rings

SONET/SDH is historically the dominant telecom transport infrastructure for backbone networks, and it is optimized for reliable delivery of voice and private-line services. Efficient utilization of the existing infrastructure through novel methods and algorithms can lead to higher revenue, which is attractive for network operators. In this study, we examine a network of inter-connected SONET/SDH rings that use dual-node interconnection employing the drop-and-continue facility, which is the de-facto standard for interworking SONET/SDH protection architectures. We develop an efficient algorithm for provisioning in such a network while keeping fragmentation of capacity low and taking into account the various constraints imposed by the underlying physical layer. We examine the case of dual-node-interconnected ring networks employing both contiguous and virtual concatenation (a next-generation SONET/SDH architecture), and as expected, we discover that provisioning higher-bandwidth connections with virtual concatenation offers significant improvement. The stringent time-slot alignment and contiguity constraints imposed by contiguous concatenation are further compounded by the constraints imposed by the ring interworking architecture, and virtual concatenation allows capacity to be used more efficiently.