Optical Multicast Routing under Light Splitter Constraints

In network communications, there are many methods to exchange packets to deliver data from sources to destinations. During the past few years, we have observed the emergence of new applications that use multicast transmission. Multicasting requires “multicast routing”, to deliver packets to a “group” of hosts, scattered throughout the Internet. For a multicast routing algorithm to be applicable in optical networks, it must route data only to group members, optimize and maintain loop-free routes, and concentrate the routes on a subset of network links. For an all-optical switch to play the role of a branching router, it must be equipped with a light splitter. Light splitters are expensive equipments and therefore it will be very expensive to implement splitters on all optical switches. Optical light splitters are only implemented on some optical switches. That limited availability of light splitters raises a new problem when we want to implement multicast protocols in optical network (because usual multicast protocols make the assumption that all nodes have branching capabilities) Another issue is the knowledge of the locations of light splitters in the optical network. Nodes in the network should be able to identify the locations of light splitters scattered in the optical network so it can construct multicast trees. This means that any node must be able to identify if other nodes in the network are multicast capable optical cross connect MC-OXC or multicast incapable ordinary cross connect OXC. These problems must be resolved by implementing a multicast routing protocol that must take into consideration that not all nodes can be branching node. As a result, a new signaling process must be implemented so that light paths can be created, spanning from source to the group members.