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Hybrid Scheduling for Unicast and Multicast Traffic in Broadcast WDM Networks
Wen-Yu TSENG Sy-Yen KUO
IEICE TRANSACTIONS on Communications
Publication Date: 2000/10/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Advanced Internetworking based on Photonic Network Technologies)
WDM, local area network, wavelength division multiplexing, media access protocol, multicast traffic,
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Session length and group size are two most significant factors in achieving efficient scheduling for unicast and multicast traffic in single-hop wavelength division multiplexing (WDM) local area networks (LANs). This paper presents a hybrid protocol to schedule both unicast and multicast traffic in broadcast WDM networks. The protocol makes an important assumption that unicast traffic is the major portion of the overall traffic and is usually scheduled with a pre-allocation-based protocol. On the other hand, multicast traffic is a smaller portion of the overall traffic with multicast sessions and multicast groups, and is scheduled with a reservation-based protocol. The concept of multicast threshold, a function of random variables including the multicast session length and the multicast group size, is also proposed to partition the multicast traffic into two types. If the transmission threshold of a multicast request is larger than the multicast threshold, the request is handled with a reservation-based protocol. Otherwise, the multicast request is handled similar to unicast traffic; that is, each packet in the multicast session is replicated and sent to the unicast queues of destinations. The results show that the hybrid protocol can achieve better channel utilization efficiency and packet delay for unicast traffic under the multicast scenarios with moderate session length and group size. However, separate scheduling or broadcasting will be more suitable for a multicast scenario with very large session length and group size, which is not common on most realistic networks.