Dynamic lightpath protection in WDM optical networks using ant-based mobile agents

In this paper, we consider the problem of dynamic lightpath protection in survivable WDM networks with single link failure model. Our work concerns in how to dynamically determine a protection cycle to establish a dependable lightpath with fault-tolerance requirement. This problem is identified as NP-complete, thus a heuristic for finding near optimal solution with reasonable computation time is usually preferred. Inspired from the principle of ant colony optimization, we develop in this paper an ant-based mobile agents algorithm for this problem with improved blocking performance. To enable the new ant-based algorithm, we propose to use on each network node both a routing table that contains a set of feasible cycles between source destination nodes and also a pheromone table for mobile agents. By keeping a suitable number of mobile agents in a network to continually and proactively update the cycles in a routing table based on the current network congestion state, the routing solution of a connection request can be obtained based on simply a local searching with a reasonable computation time. Extensive simulation results upon the ns-2 network simulator show that our new algorithm can achieve a significantly lower blocking probability than the promising algorithm for dynamic lightpath protection with a comparable computation complexity.