Optimal Resource Placement in Multifiber Mesh-Survivable WDM Networks

Demands for networks of higher and higher capacities are increasing dramatically with the growth of the Internet and the World Wide Web. All-optical wavelength-division multiplexing (WDM) networks is the most promising candidate to fulfill the bandwidth requirement of the Broadband Integrated Services Digital Network (B-ISDN). In WDM networks, the huge bandwidth available on an optical fiber is divided into multiple channels. Each channel, with bandwidth up to several gigabits/second, is used to communicate between two network stations. As the capacity of WDM networks is becoming larger, healing an optical network in less time upon equipment and fiber failures becomes a critical requirement, because large amount of data would be lost during the failures. Mesh-based restorable network architectures have been intensively researched on non-WDM networks in the literature [4, 5]. In such networks the spare resources on one link contributes to the survivability of many other links. Failed connections can be efficiently rerouted because of its highly diverse topology. Mesh-restorable networks either reroute failed connections over a set of replacement paths through the spare capacity of a network between the two nodes terminating a link, referred to as link restoration, or over a set of replacement paths between all source and destination nodes affected by a failure, referred to as path restoration. WDM mesh-type networks are investigated in [3]. Integer Liner Programming (ILP) formulations are developed for the wavelength utilization for a set of static demands for three different restoration approaches. The results show that path restoration is preferred over link restoration in terms of resource requirement. However, only single fiber WDM networks without wavelength converters are considered in the ILP formulations, which is usually not the case in reality. The blocking probability in such networks could be too high to be practical because of the wavelength continuity constraint, i.e., the same wavelength must be assigned to all the links on a path to set up a connection between a source-destination (s-d) pair.