The optimized prioritized iSLIP scheduling algorithm for input-queued switches with ability to support multiple priority levels

An increasing number of Internet routers use a crossbar switch to interconnect line cards. These systems usually use input queuing combined with virtual output queuing, so that with a suitable scheduling algorithm like iSLIP they can achieve nearly 100% throughput. But many applications use multiple classes of traffic with different priority levels. So there is an increasing demand for switch fabrics that can support prioritized traffic. Despite its good performance under traffic with one class of service, modified versions of iSLIP like prioritized iSLIP face a noticeable decrease in performance under prioritized traffic and other algorithms like weighted iSLIP that have high performance are hard to implement. A starvation free scheduling algorithm, optimized prioritized iSLIP, which has a dramatically improved performance in comparison with prioritized iSLIP is introduced. Because its implementation is similar to iSLIP, it is fast and easy to implement in hardware.