Integrated Queuing and Scheduling for Unicast and Multicast Traffic in Input-Queued Packet Switches

This paper presents the integrated queuing and scheduling for an N × N input-queued packet switch that efficiently supports both unicast and multicast traffic. Each input port maintains two sets of queues each for unicast and multicast traffic. For unicast traffic, we deploy the wellknown virtual output queuing scheme. For multicast traffic, we propose a novel queuing scheme in which a small number of load-balanced queues are allocated at each input port. This is sufficient to obtain a high switch throughput and a low packet delay. The scheduling of unicast and multicast traffic is integrated within one switch fabric. Two specific issues are addressed regarding to the integrated scheduling: 1) the service ratio of unicast traffic to multicast traffic, and 2) the integration strategy between unicast and multicast scheduling. The first issue relates to the internal switch fabric bandwidth allocation. We define a new concept called working interval. As long as the service ratio lies in the working interval, a 100% throughput is able to achieve. The second issue concerns how the unicast and multicast scheduling interact with each other. Two integration strategies were designed, light coupled and tight coupled. Both are able to achieve low packet delay. The analytical and simulation results show that the proposed integrated queuing and scheduling performs well in the present of diverse traffic patterns.