We consider dynamically changing multicast trees (light-trees) in two-layer optical-beared
grooming-capable networks. The continuous changing of the
tree ?leaves? causes the degradation of the tree in time. Therefore, a huge amount
ofnetwork 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.