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.

We study the problem of reliably provisioning traffic in high-capacity backbone mesh networks supporting virtual concatenation (VCAT). VCAT enables a connection to be inversely multiplexed on to multiple paths, a feature that has many advantages over conventional single-path provisioning. We propose improved routing algorithms which use minimum- cost flow to find efficient collections of paths that satisfy the traffic requests. We first investigate the performance of our scheme under a uniform setting with symmetric traffic distribution and equal link capacities. We then apply our algorithm in a more realistic setting with asymmetric traffic and differing link capacities. Our algorithm is effective in both the uniform and non-uniform settings, and is much more effective than previously proposed schemes. Our study in the non-uniform setting is significant as it gives insight into the performance of our algorithm under more realistic scenarios.

We investigate the problem of reliable multi-path provisioning of traffic in high-capacity optical backbone mesh networks, e.g., next-generation SONET/SDH networks supporting virtual concatenation (VCAT). VCAT enables a connection to be inversely multiplexed on to multiple paths. As a result, a connection can be provisioned more flexibly, and such a multi-path provisioning approach may lead to significantly improved performance over the conventional single-path provisioning approach. This multi-path provisioning approach may also be applicable to other mesh networks such as those employing optical wavelength-division multiplexing (WDM) and multi-protocol label switching (MPLS), where the bandwidth of a connection to be provisioned exceeds the available capacity on any path based on current network state. We propose effective multi-path bandwidth as the metric to provision a connection on to multiple paths while satisfying its reliability requirements (measured in terms of availability). We show that effective multi-path bandwidth provides more flexibility and lower blocking probability without the cost and complexity associated with traditional protection schemes developed for optical WDM and MPLS networks.