A Parallel Route Assignment Algorithm for Fault-Tolerant Clos Networks in OTN Switches

Abstract

The three-stage fault-tolerant Clos network, where extra switch modules exist in the middle stage in case of switch failures, is widely used in the design of OTN switches. This paper proposes a route assignment algorithm for such Clos networks by solving its counterpart in edge-coloring problem. Based on complex coloring, a novel edge coloring method, the proposed algorithm possesses two properties. First, our algorithm can make full use of extra switch modules in the middle stage of Clos network. The extra switch modules provide additional colors for edge coloring, which help to reduce the running time of the coloring process remarkably. Second, our algorithm can be implemented in a parallel manner to further shorten the running time. The proposed routing algorithm achieves a low complexity of $O(\frac{\sqrt{N}(m-1)}{m-1+(m-\sqrt{N}){\log }N}{\log }N)$O(N(m-1)m-1+(m-N)logNlogN), where $N$N is the network size and $m$m is the number of switch modules in the middle stage. The performance of our algorithm has been verified by extensive simulation experiments.