Enhancing Fault Tolerance and Resource Utilization in Unidirectional Quorum-Based Cycle Routing

Abstract

Cycle-based optical network routing, whether using synchronous optical networking rings or p-cycles, provides sufficient reliability in the network. Light trails forming a cycle allow broadcasts within a cycle to be used for efficient multicasts. Optimal communication quorum sets forming optical cycles based on light trails have been shown to flexibly and efficiently route both point-to-point and multipoint-to-multipoint traffic requests. Commonly, cycle routing techniques use pairs of cycles to achieve both routing and fault tolerance, which use substantial resources and create the potential for underutilization. Instead, we intentionally utilize $R$ redundancy within the quorum cycles for fault tolerance such that every point-to-point communication pairs occur in at least $R$ cycles. We develop a generalized $R$ redundancy cycle technique that provides optical networks high fault-tolerant communications capability. When applied using only the single unidirectional cycles rather than the standard paired cycles, the generalized $R$ redundancy technique has been shown to almost halve the necessary light-trail resources in the network. However, due to unidirectional nature, a small percentage of node pairs for one-to-one communication may not have exactly two paths. For this reason, we further develop a greedy cycle direction heuristic and show a reduction of missing pairs. More importantly, we show that the resource requirement is reduced while maintaining the fault tolerance and dependability expected from cycle-based routing. The result is a set of cycles with 96.6%–99.37% fault coverage, while using 42.9%–47.18% fewer resources.