LOGICAL TOPOLOGY DESIGN FOR SURVIVABILITY IN IP-OVER-WDM NETWORKS

Abstract

IP-over-WDM networks integrate Wavelength Division Multiplexing (WDM) technology with Internet Protocol (IP) and are widely regarded as the architecture for the next generation high-speed Internet. The problem of designing an IP-over-WDM network can be modeled as an embedding problem in which an IP network is embedded in a WDM network by establishing all optical paths between IP routers in the WDM network. Survivability is considered a vital requirement in such networks, which can be achieved by embedding the IP network in the WDM network in such a way that the IP network stays connected in the presence of failure or failures in the WDM network. Otherwise, some of the IP routers may not be reachable.

The problem can be formulated as an Integer Linear Program (ILP), which can be solved optimally but is NP-complete. In this thesis, we have studied and proposed various efficient algorithms that can be used to make IP-over-WDM networks survivable in the presence of a single WDM link (optical fiber cable or cables) failure.

First we evaluate an existing approach, named Survivable Mapping Algorithm by Ring Trimming (SMART), which provides survivability for an entire network by successively considering pieces of the network. The evaluation provides much insight into the approach, which allowed us to propose several enhancements. The modified approach with enhancements leads to better performance than the original SMART.

We have also proposed a hybrid algorithm that guarantees survivability, if the IP and the WDM networks are at least 2-edge connected. The algorithm uses a combination of proactive (protection) and reactive (restoration) mechanisms to obtain a survivable embedding for any given IP network in any given WDM network.

Circuits and cutsets are dual concepts. SMART approach is based on circuits. The question then arises whether there exists a dual methodology based on cutsets. We investigate this question and provide much needed insight. We provide a unified algorithmic framework based on circuits and cutsets. We also provide new methodologies based on cutsets and give a new proof of correctnessof SMART. We also develop a method based on incidence sets that are a special case of cutsets. Noting that for some IP networks a survivable embedding may not exist, the option of adding new IP links is pursued. Comparative evaluations of all the algorithms through extensive simulations are also given in this dissertation.