The ISLIP Algorithm Based On The Scheduling Of The Top Priority

A switch fabric is a core element of high performance switches and routers. How to obtain a high transmitting speed on the premise of guaranteeing quality of service is a hot and difficult topic of network researching over the past few years. The scheduling algorithms of switch fabric are responsible for transferring the cells from inputs to outputs, therefore they play a key role in increasing the utilization of bandwidth and guaranteeing quality of service.First, this paper introduces the queuing and switching structures. The emphases are placed on input queuing and crossbar structure which are widely used in switches. Then a survey is made on the scheduling algorithms of crossbar structure. Algorithms supporting best-effort service and guaranteeing quality of service are separately introduced. Thereafter the famous iSLIP(Iterative Serial Line Interface Protocol) algorithm is deeply described and its performances are analyzed.Because some services require to be transmitted immediately in some industrial environment, giving precedence to the dispatching of the highest priority business is discussed in this paper. And a scheme is proposed for transmitting highest priority cells in "real time channel" to decrease cells delay and get "real-time" performance.This paper designs a new algorithm for the above scheme, analyzes its performance by computing some parameters such as complexity, throughput and delay, and compares some typical futures between this scheme and priority iSLIP. Especially, the delays with highest priority cells in the two are differentiated. This theoretical analysis shows the above scheme can further decrease the delay of the services with highest priority, with other services being not seriously influenced. Of course, the deficiency of this proposal is also discussed in the paper.At the end of the paper, simulation experiments are carried out to simulate the proposal with SIM simulation software. Simulation data is obtained by simulating the process of switches with different port number under different traffics. The iSLIP algorithm based on priority is also simulated. Finally, through the comparison of these experiment results, the consistence with the theoretical analysis is proved.