Dynamic RWA Based on the Combination of Mobile Agents Technique and Genetic Algorithms in WDM Networks with Sparse Wavelength Conversion

Abstract

SummaryGenetic Algorithms (GA) provide an attractive approach to solving the challenging problem of dynamic routing and wavelength assignment (RWA) in optical WDM networks, because they usually achieve a significantly low blocking probability. Available GA-based dynamic RWA algorithms were designed mainly for WDM networks with a wavelength continuity constraint, and they can not be applied directly to WDM networks with wavelength conversion capability. Furthermore, the available GA-based dynamic RWA algorithms suffer from the problem of requiring a very time consuming process to generate the first population of routes for a request, which may results in a significantly large delay in path setup. In this paper, we study the dynamic RWA problem in WDM networks with sparse wavelength conversion and propose a novel hybrid algorithm for it based on the combination of mobile agents technique and GA. By keeping a suitable number of mobile agents in the network to cooperatively explore the network states and continuously update the routing tables, the new hybrid algorithm can promptly determine the first population of routes for a new request based on the routing table of its source node, without requiring the time consuming process associated with current GA-based dynamic RWA algorithms. To achieve a good load balance in WDM networks with sparse wavelength conversion, we adopt in our hybrid algorithm a new reproduction scheme and a new fitness function that simultaneously takes into account the path length, number of free wavelengths, and wavelength conversion capability in route selection. Our new hybrid algorithm achieves a better load balance and results in a significantly lower blocking probability than does the Fixed-Alternate routing algorithm, both for optical networks with sparse and full-range wavelength converters and for optical networks with sparse and limited-range wavelength converters. This was verified by an extensive simulation study on the ns-2 network simulator and two typical network topologies. The ability to guarantee both a low blocking probability and a small setup delay makes the new hybrid dynamic RWA algorithm very attractive for current optical circuit switching networks and also for the next generation optical burst switching networks.

Ant-Based Alternate Routing in All-Optical WDM Networks

“…It is noticed that we can apply more advanced techniques of alternate routing methods to improve furthermore the performance of our HABR algorithm such as routing using neighborhood information [8], or another techniques to evaluate the goodness of a route to introduce the load balancing as in [12]- [14]. However, these problems are out of scope of this paper.…”

“…The parameter ϕ should be chosen such that the shorter route has a larger goodness value, while for two routes with the same length, the route with a larger number of idle wavelengths gets a larger goodness value. It is formally proved in [14] that the value of ϕ should be selected based on the following inequality:…”

A novel dynamic survivable routing in WDM optical networks with/without sparse wavelength conversion

“…Thus, in a WDM network with sparse wavelength conversion, the dynamic survivable routing problem needs deliberate study to take full advantage of the gain from wavelength conversion [8,9]. With such an observation, we proposed an RWA algorithm based on the combination of mobile agents technique and GA [10]. However, that paper only considered the normal nonsurvivable routing problem; the fitness function in the algorithm may be not good because it has to compute two values for each route with wavelength converters, one for the case with wavelength conversion and another for the case without.…”

“…It then needs to compute the cost of the best cycle (10, 12, 11, 13, 10), which represents two disjointlink routes: (10, 12, 11) and (10,13,11).…”

“…If the protected connection from node 6 to node 11 was established according to case (b), the establishment of the protected connection for this request requires two new channels for the backup lightpath and two new channels for the primary lightpath (for both cases we choose (10,12,11) as the primary lightpath and (10, 13, 11) as the backup lightpath and vice versa). Thus, it needs to use 2 + 4 + 2 = 8 channels for primary lightpaths and 4 + 1 + 2 = 7 channels for backup lightpaths for three requests.…”