Dual-CISTs: Configuring a Protection Routing on Some Cayley Networks

A set of $k~(\geqslant 2)$ spanning trees in the underlying graph of a network topology is called completely independent spanning trees, (CISTs for short), if they are pairwise edge-disjoint and inner-node-disjoint. Particularly, if $k=2$ , the two CISTs are called a dual-CIST. However, it has been proved that determining if there exists a dual-CIST in a graph is an NP-hard problem. Kwong et al. [IEEE/ACM Transactions Networking 19(5) 1543–1556, 2011] defined that a routing is protected, if there is an alternate with loop-free forwarding, when a single link or node failure occurs. Shortly afterward, Tapolcai [Optim. Lett. 7(4) 723–730, 2013] showed that a network possessing a dual-CIST suffices to establish a protection routing. It is well-known that Cayley graphs have a large number of desirable properties of interconnection networks. Although many results of constructing dual-CISTs on interconnection networks have been proposed in the literature, so far, the work has not been dealt with on Cayley graphs due to that their expansions are in exponential scalability. In this paper, we try to make a breakthrough of this work on some famous subclasses of Cayley graphs, including alternating group networks, bubble-sort network, and star networks. We first propose tree searching algorithms for helping the construction of dual-CISTs on low-dimensional networks. Then, by inductive construction, we show that dual-CISTs on high-dimensional networks can also be constructed agreeably. As a result, we can configure protection routings by using the constructed dual-CISTs. In addition, we complement some analysis with a simulation study of the proposed construction to evaluate the corresponding performance.