Reconfiguration of Survivable IP Over WDM Networks

Network reconfiguration has become a fundamental operational function for transparent IP over WDM networks in order to optimize network resource utilization and traffic engineering goals subject to frequent traffic and network state changes. However, it remains very challenging to automate the network reconfiguration process without disrupting existing traffic and incurring heavy overhead. In this paper, we present a novel mechanism for the important IP layer virtual topology reconfiguration task for IP over DWDM networks. In such networks, virtual topology reconfiguration is achieved by setting up a set of new lightpaths to form the new virtual topology and tearing down the lightpaths in the existing virtual topology. The main idea behind the mechanism is to make use of the backup lightpaths that are commonly pre-allocated to protect the network from failures. Our goal is to design the optimal reconfiguration process to achieve hitless reconfiguration, i.e., zero traffic disruption during the reconfiguration. We formulate and decompose the problem into two optimization problems: the Reconfiguration grouping problem that aims at minimizing the reconfiguration steps, and the Reconfiguration sequencing problem that aims at minimizing the network resource overhead during the reconfiguration process. We first prove that these two problems are NP-hard and then design several efficient heuristic algorithms. Rollout algorithms are applied to the heuristics to improve the solution quality. Extensive simulation results demonstrate the efficiency of the proposed reconfiguration mechanism and algorithms.