Capacity-bounded lightpath routing in WDM optical networks

Abstract

To meet the increasing user bandwidth demands, the ICT networks are constantly expanding. The optical fiber technology has completely revolutionized the bandwidth capacity of both the core networks and the access networks. In core networks, the optical links provide very high bandwidth connectivity over long distance. Thus, any link failure due to disastrous events like earthquake, flood, landslide etc. can lead to massive service outages and huge fiscal losses. Normally, optical fibers are laid in 1 + 1 configuration to route the traffic to the alternate path in such scenario. However, a natural disaster event may lead to simultaneous failure of multiple lightpaths. Therefore, routing algorithm, running on network nodes (routers or switches), are required in such case to establish new routes. Nevertheless, generally the routing schemes follow the least hop count and shortest distance approach to route the traffic to another backup path. Nonetheless, this approach may result in congestion on some links while other links may have unutilized capacity. This also makes it progressively tougher to fit more connection requests from the access network. Hence, implementation of more advanced path computation capabilities is required at the network nodes of the core network to ensure efficient routing of network traffic in disastrous scenario. This problem is referred to as capacity-bounded lightpath (CBL) problem. We proposed an exact algorithm which addresses this problem by considering the channel capacity of each link in addition to distances. The performance of the proposed algorithm is evaluated through simulation for three parameters: link capacity, connection requests and un-used links. It is revealed that existing shortest path algorithm improves the performance in terms of blocking probability of links and lightpaths at the cost of underutilization of the network capacity. Whereas, proposed algorithm regulates the capacity utilization by prioritizing link capacity over link length to establish more optimal shortest lightpath against connection requests.