Research Of The SACK Algorithm Based On Network Congestion Control

Since 1990s, the internet based on TCP protocol has shown explosive growth. New-style network application continuously appears, user number increases rapidly, thus initiated network congestion has become bottleneck problem of network development and application. Network congestion is easy to lead to the performance decreasing of Qos (Quality of Service)just as transmission delay and throughput, and the network resources utilization rate (bandwidth, cache and so on) is severely affected. It's great significance for improving network performance to solve the problem of congestion effectively. And how better to prevent and control congestion has been the hot issue of international network in recent years.Against this background, the defects of Sack algorithm (Selective acknowledge) have been studied deeply in the paper, an improved algorithm has been proposed. The theoretical analysis and network simulation results show that the improved algorithm for SACK has better network performance in most cases.The central work for this paper is: Firstly, recent researching progress of congestion control algorithm has been introduced in the paper, especially the congestion control algorithm based on source and link are emphasized. Secondly, the SACK algorithm is studied, an improved algorithm for SACK has been proposed for its defects. At last, the NS (Network Simulator) network software is used to simulate its performance of the link utilization ratio, the relative fairness and the dropped packets rate. The simulation results show that the improved algorithm for SACK can make up for the defects of the SACK algorithm to some extent, and improve the network transmission performance.The research work and conclusions of the paper is certain reference value for solving the internet congestion problem. Plenty of experimental verification has not been done in extensive network environments, so much remains to be further study and improvement.