The most effective way of providing popular user services such as high-definition television, video conferencing and distributed gaming over the Internet is multicasting. Protecting multicast sessions against single link failure or a fiber cut in the WDM optical backbone is thus vital. Protection schemes involve reserving resources for backup paths that remain idle during normal fault-free operation. It is thus important to design protection or survivability schemes that consume as few extra resources as possible. A number of protection schemes for multicast sessions exist in the literature but only few can provide rapid recovery. In this paper we propose a new offline strategy for ensuring survivability of multicast traffic that can aid rapid recovery from a link failure. Our strategy is designed to achieve significant resource saving while providing recovery speed comparable to 1:1 dedicated path protection. We first propose an Integer Linear Program formulation to solve the problem optimally for small networks and then a heuristic for large networks. Performance comparisons show that our heuristic performs better than two well-known heuristics and also produces near optimal results. Time complexity analysis further shows that our heuristic runs in polynomial time.

在互联网上提供流行的用户服务（例如高清电视，视频会议和分布式游戏）的最有效方法是多播。因此，保护​​多播会话免受单链路故障或WDM光骨干网中光纤的损坏至关重要。保护方案包括为备用路径保留资源，这些备用路径在正常无故障运行期间保持空闲状态。因此，设计消耗尽可能少的额外资源的保护或生存方案非常重要。文献中存在许多用于多播会话的保护方案，但是只有少数可以提供快速恢复。在本文中，我们提出了一种新的脱机策略，以确保多播流量的生存能力，从而有助于从链路故障中快速恢复。我们的策略旨在节省大量资源，同时提供与1：1专用路径保护相当的恢复速度。我们首先提出一个整数线性程序公式，以针对小型网络最优地解决问题，然后针对大型网络进行启发式。性能比较表明，我们的启发式算法比两个著名的启发式算法性能更好，并且还产生了接近最佳的结果。时间复杂度分析进一步表明，我们的启发式算法在多项式时间内运行。