Improved Quasi-Path Restoration in Mesh Networks

Abstract

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 ( 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.

A comparative study of restoration schemes and spare capacity assignments in mesh networks

“…The subpath from the source (or the destination) to the critical node on the same side, namely, 1-3-5 (or 7-9) will remain intact. There are two variations of QPR scheme known as OQPR [4] and IQPR [5]. In OQPR, all the intact subpaths of the disrupted paths will be on the same side of the failed link.…”

“…Note that the restoration path(s) found using OQPR or IQPR may suffer from backhauling. Both (online) schemes have a time complexity of O(n 3 ) [4], [5] which makes them computationally very efficient. An added advantage of these schemes is the integrality of restored traffic flows.…”

“…In QPR, the target node pair consists of the source and the critical node on the destination side or the destination and the critical node on the source side. The criteria used to define target node pairs for OQPR and IQPR are the same as those given in [5], [23]. In PR and LDPR, the target nodes are the sources and the destinations of the disrupted paths.…”

“…LR is computationally very efficient, fast, simple, and scalable but expensive in network resources whereas PR is known to be very economical in network resources but computationally very hard and complex. Recently, two new schemes, namely, original quasipath restoration (OQPR) and improved quasi-path restoration (IQPR) have been proposed [4], [5], which are tradeoffs between LR and PR. These schemes are computationally very Destination Source Alternate path using path restoration scheme Alternate path using link−disjoint path restoration schem Alternate path using quasi−path restoration scheme Primary path (working path) Alternate path using link restoration scheme efficient, fast, simpler than PR and scalable, which make them good alternatives to PR.…”