The FIFO Research Based On The ISLIP Algorithm

A switching structure is a crucial element of routers and switches. How to obtain a high transmitting speed while guaranteeing QoS (Quality of Service) is a hot topic of network research in recent years. The scheduling algorithms of switch fabric are responsible for transferring the cells from input port to output port, therefore it plays a crucial role in improving the bandwidth utilization and quality of service of switch devices. The iSLIP algorithm, a classical scheduling algorithm used to solve the scheduling problems of high-speed router and switch fabric, has a high throughput, good latency characteristics, easy in hardware implementation, and being used widely in practice. it is also a hot spot of today's researches.This paper first describes the switch fabric and queuing structure, focusing on describing the practical application of a broader structure of the input queue and cross-switch fabric, then describes some existing packet scheduling algorithms such as PIM, RRM, and iSLIP, revealing their scheduling processes, advantages and disadvantages. An in-depth analysis for the performance of iSLIP is especially made.FIFO(First In First Out)is a basic requirement can be seen as a basic QoS requirement on many occasions. For example, businesses with same priority generally require FIFO services. Through the in-depth analysis in the scheduling process of the iSLIP algorithm, it is found that the algorithm can not guarantee the FIFO requirement and therefore a new FIFO-iSLIP algorithm is proposed. This improved algorithm maintains the original iSLIP priority scheduling mechanism and at the same time ensures the FIFO feature, ensuring an orderly transfer for real-time businesses, without too much increase in the complexity of the original algorithm. This article provides the design of the FIFO-iSLIP algorithm and the analyses of performances (especially the transmission delay), and compares them with the iSLIP algorithm. Through theoretical analysis it is found that the FIFO-iSLIP algorithm can further reduce the latency on many occasions, especially for light-load businesses. Of course, the disadvantages of FIFO-iSLIP algorithm are also explored.In order to verify the FIFO-iSLIP algorithm, we spent a great effort on analyzing the network simulation software SIM developed by the Stanford University. With different flow models and different number of ports, we use this simulation tool to simulate the FIFO-iSLIP algorithm and the iSLIP algorithm.The simulation results prove the above theoretical analysis.