Approaching Work-Conserving Scheduling Algorithm for Mixed Unicast and Multicast in Combined Input and Crosspoint Queued Switch

A novel scheduling algorithm supporting mixed unicast and multicast traffic and featured by the longest virtual queue first (LVQF) was proposed for combined input and crosspoint queued (CICQ) architecture. Considering the differences between unicast and multicast traffic, LVQF takes the virtual queue length as the weight value for unicast and multicast queues. The weight setting of LVQF coordinates the fairness of unicast and multicast scheduling efficiently. Moreover, the design of LVQF is characterized by approaching the inherent work-conserving of the output queued architecture. By balancing the occupancy of crosspoint buffers, LVQF maintains the switch operating in a work-conserving state to the largest extend. By introducing the traffic regulation module in CICQ, an enhanced approaching work-conserving (AWC) algorithm developed from LVQF (AWC-LVQF) is proposed to further approach the work-conserving state. Simulation results demonstrate that LVQF and AWC-LVQF algorithms can significantly improve the average latency performance with respect to the existing popular algorithms for CICQ switch. In particular, the performance improvement enlarges as the ratio of multicast traffic increases.