Optimized Designs of p-Cycles for Survivable Multicast Sessions in Optical WDM Networks

Network service outage causes tremendous revenue loss and service disruption for both unicast and multicast traffic. In particular, multicast traffic suffers more in network failures than unicast traffic does, because a link in a multicast tree might carry traffic to multiple destinations. Hence, network survivability is crucial to provisioning of multicast sessions in optical WDM networks. The preconfigured protection cycle (p- cycle) method, originally proposed for unicast traffic protection [1] by W. D. Grover, combines the rings´ simplicity, fast speed in switching, and the meshes´ flexibility in routing, efficiency in resource utilization. Although p-cycles have been extensively studied for unicast traffic protection, they have been rarely applied to multicast traffic protection. We have recently proposed applying link p-cycle based approaches, namely Dynamic p-Cycle (DpC) design and link p-cycle based Protected Working Capacity Envelope (PWCE) design to dynamic provisioning of survivable multicast traffic [2]. In this paper, we analyze the existing multicast protection approaches and present Integer Linear Programming (ILP) methods for p-cycle based protection of static multicast sessions. We consider the approaches of p-cycle based ILP joint optimization (JOP) and Non-joint optimization (NJOP), and the approach of p-cycle based ILP optimization of spare capacity (SOP). These ILP optimization methods serve as the bench mark for p-cycle based heuristic algorithms [3]. We also compare the results with that of the Path Pair Protection approach in [4] . We show that the p- cycle based JOP offers the least total capacity consumption, compared with other optimization approaches.