Restoration of multi-cast trees in optical-beared grooming-capable two-layer networks

We consider dynamically changing multicast trees (light-trees) in two-layer optical-beared grooming-capable networks. The continuous changing of the tree ldquoleavesrdquo causes the degradation of the tree in time. Therefore, a huge amount of network resources can be spared by reconfigurations performed periodically or upon failures and reparations. In this paper we focus onto restoration of trees if a link (or any other network element) fails. The failures are more critical if they affect the tree closer to its root, while less critical if closer to a leave. We propose and evaluate four simple restoration strategies and investigate their performance for different multicast routing algorithms.