Improved Quasi-Path Restoration in Mesh Networks

Restoration of disrupted traffic is critical in today´s high-speed self-healing telecommunication networks. A restoration scheme dynamically discovers alternate paths bypassing the failed component. This paper presents an (online) improved quasi-path restoration (IQPR) scheme. IQPR is derived from the two-commodity max-flow algorithm. The running time complexity of IQPR is O(|V|³). Therefore, IQPR is computationally more efficient and more scalable than path restoration (PR). IQPR is faster (in restoration speed) and less complex than PR, and more economical (in spare capacity requirement) than link restoration (LR). Thus, it provides a good alternative to PR when quick restoration of disrupted traffic is desired. The (offline) spare capacity planning problem deals with the allocation of spare capacity to each link in the network, such that the spare capacity requirement is minimized, while guaranteeing the desired level of restoration in the event of a link failure. The spare capacity allocation problems for LR, original quasi-path restoration (OQPR), IQPR, link-disjoint path restoration (LDPR) and PR are formulated as integer linear programming problems. Numerical results illustrate that the restoration schemes studied can be sorted from the least efficient to the most efficient (in the spare capacity requirement) in the following order: LR, OQPR, IQPR, LDPR and PR. The experimental analysis shows that network topology and demand patterns have a significant impact on the spare capacity savings offered by one scheme over the other. Merits and demerits of these schemes are also discussed.