p-cycle network design with hop limits and circumference limits

Abstract

p-Cycles offer an approach to protection of optical transport networks which is as fast as a ring-based network but with mesh-like capacity efficiency. One misconception about p-cycle designs seems to be that they involve long protection paths, even though it is trivial to limit the circumference of cycles admitted to the design problem. In addition, through straddling span considerations the average protection path on a p-cycle is actually shorter than in a corresponding ring. Nonetheless there are some open questions regarding path and cycle circumference limit effects with p-cycles. One question is whether p-cycle networks exhibit a "threshold hop-limit" effect corresponding to that well-known aspect of spanrestorable mesh networks. (Beyond the threshold hop-limit there are negligible savings in capacity.) To study this question we extend the existing p-cycle network design theory to include the capability of direct restriction of protection path lengths, rather than indirect restriction through circumference limits. A second, quite practical question is to ask how well simple limitation of cycle circumferences serves as a surrogate for a more involved design method of directly asserting a hop (or distance) limit on the maximum length of protection paths. The answers to the questions and the methods developed to address them both enhance our ability to design p-cycle networks in which optically transparent length may affect transmission quality, or where the length of protection paths may affect cost if regeneration is required en route of a protection path. The main findings are that p-cycles do exhibit threshold hop-limiting effects (at about two or three hops above those in corresponding mesh networks) and that cycle limiting is a simple and effective surrogate for direct limitation on path lengths in p-cycle design problems.

Removal of Loop Back in p-cycle Protection: Second Phase Reconfiguration

“…To obtain the optimal solution for the configuration of p-cycle many heuristics have been developed [14]- [16]. To limit the protection path length of the p-cycle 'hop limit' and 'circumference limit' designs of the p-cycles are proposed [17]. Recently the span protection technique of p-cycle has been extended to provide node [18] and path protection [19]- [20] also.…”

Implementing Protection Classes through p-Cycles in Impairment-Constrained Optical Networks

“…Several ILP algorithms have been proposed to find p-Cycles without enumeration in WDM networks [8], [9], [10], but they assume that the traffic demand matrix is known and do not consider an all-optical environment with physical layer impairments. In [2] we developed an ILP formulation that applies to all-optical networks and preconfigures the p-Cycles for any dynamic traffic, with the assumption that all users have the same survivability requirement.…”

A New ILP-Based p-Cycle Construction Algorithm without Candidate Cycle Enumeration

“…Because of its outstanding performance on both recovery speed and capacity efficiency, p-cycle has attracted intensive research interests [3][4][5][6][7][8][9][10][11][12][13][14] since it was first introduced in 1998 [1]. Recently, p-cycle was also extended to path/segment protection at the cost of slower recovery speed [15][16].…”