Nonblocking Multicast Communication

Abstract – A main requirement in high performance networks is multicast communication, which involves transmitting information from a single source node to multiple destination nodes. A multicast assignment is a mapping from a set of network nodes called as source nodes, to a maximum set of network nodes called destination nodes with no overlapping allowed among the destination nodes of different source nodes A network is said to be nonblocking for multicast assignments, if for any legitimate multicast connection requests from a source node to a set of destination nodes, it is always possible to provide connection path through the network to satisfy the connection request without any disturbance to the existing connections. If the path selection

It is always desirable for an optical network to be nonblocking as blocked data will be lost due to lack of optical buffer. A network is said to be nonblocking for multicast assignments, if for any legitimate multicast connection requests from a source node to a set of destination nodes, it is always possible to provide connection path through the network to satisfy the connection request without any disturbance to the existing connections. If the path selection follows a routing algorithm to maintain nonblocking connecting capability, the network is said to be wide-sense nonblocking. In this paper, we study about wide-sense nonblocking multicast communication in wavelength reusable multi-carrier distributed (WRMD) wavelength division multiplexing (WDM) linear array, unidirectional ring and bidirectional ring networks. Also, for each type of network, the necessary and sufficient conditions on the minimum number of wavelengths required to be wide-sense nonblocking for multicast communication is derived. The linear array and ring networks are popular and find application in any form of network including WAN, MAN and LAN [4-10]. We also expect the results to be obtained in this paper, is to be a representative of the performance obtainable from practical long-haul networks like mesh

This necessitates N-1 wavelengths. After the above wavelengths are modulated at its corresponding source node, connections reach RN again and undergo wavelength conversion to an unused wavelength. Then, the connections are routed to their corresponding destination. Here, all connections once again share the link connecting RN and node 1. This process needs additional N-1 wavelengths. Thus, atleast 2N-2 wavelengths are required for the above connections. At this point, when a new connection of the form arrives, it needs another new wavelength. Thus, atleast wavelengths are required for this worst case multicast assignment. Therefore, 2N-1 wavelengths are sufficient and necessary for a WRMD WDM unidirectional ring with N node to be wide-sense nonblocking for any multicast assignment.

Next, we present a simple wavelength assignment algorithm for unidirectional ring. Assume that the wavelengths available are numbered as When a new connection is requested with destination node index i, assign an unmodulated wavelength if source node index is less than destination node. Else assign an unmodulated wavelength for connection from RN to source node and after modulation again to RN. At RN, t is converted to and routed