Efficient algorithms for computing disjoint QoS paths

Networks are expected to meet a growing volume of requirements imposed by new applications such as multimedia streaming and video conferencing. Two essential requirements are support of quality of service (QoS) and resilience to failures. In order to satisfy these requirements, a common approach is to use two disjoint paths between the source and the destination nodes, the first serving as a primary path and the second as a restoration path. Such approach, referred to as path restoration, has several advantages, the major one being the ability to switch promptly from one path to another in the event of a failure. A major issue in this context is how to identify two paths that satisfy the QoS constraints imposed by network applications. Since network resources, e.g., bandwidth, are allocated along both primary and restoration paths, we need to consider also the overall network performance. Accordingly, in this paper we study the fundamental problem of finding two disjoint paths that satisfy the QoS constraints at minimum cost. We present approximation algorithms with provable performance guarantees for this fundamental network problem.