Reliable WDM Multicast in Optical Burst-Switched Networks

In this paper, we present a reliable WDM (Wavelength-Division Multiplexing) multicast protocol in optical burst-switched (OBS) networks. Since the burst dropping (loss) probability may be potentially high in a heavily loaded OBS backbone network, reliable multicast protocols that have developed for IP networks at the transport (or application) layer may incur heavy overheads such as a large number of duplicate retransmissions. In addition, it may take a longer time for an end host to detect and then recover from burst dropping (loss) occurred at the WDM layer. For efficiency reasons, we propose burst loss recovery within the OBS backbone (i.e., at the WDM link layer. The proposed protocol requires two additional functions to be performed by the WDM switch controller: subcasting and maintaining burst states, when the WDM switch has more than one downstream on the WDM multicast tree. We show that these additional functions are simple to implement and the overhead associated with them is manageable. Using the proposed protocol, member edge routers on the multicast tree is implicitly organized into a hierarchical structure dynamically. In addition, it leads to very efficient local loss recovery that results in no duplicate transmissions, no implosion and early detection of dropping. Simulations show that the proposed protocol results in a reasonable delivery latency and amount of bandwidth consumption under a various traffic load and group size.