Study Of Network Sampled Flow Timeout Strategy

With the rapid development of Internet,many kinds of Internet services come forth. Due to the large network traffic,it is very difficult to measure flow real-timed and online.In order to solve the problem,the sampling technique is proposed.Firstly we sample part of network traffic,and then use flow statistics formed from sampled packet stream to infer the flow behavior.As one of most important features of flow recognition,the timeout determines the maximal time interval between adjacent packets.When we sample packets,the sampled packets' time interval is different from the flow packets' time interval,so the flow timeout is not suitable for the sampled flow.The improper timeout can lead to flow joined or flow divided,which may reduce the estimating accuracy.In this paper,we study the network timeout strategies.The state-of-art of flow timeout strategies is concentrated on the unsampled flow.The fixed timeout strategy adopts a fixed value,and it is usually 64 second.This strategy can't change the timeout along with the network condition dynamically.MBET strategy can change the timeout based on the flow throughput dynamically.In this strategy,many parameters need to be set,and the immoderate parameters will cause the extraordinary diversities between the measurement results and the facts.The dynamical timeout strategy(DToS) deals with flows that have different rate features by using different strategy.This method could improve the performances of network measurement and the efficiency of the resource usage.At last,according to the sampling proportion and current flow timeout strategy,we propose the sampled flow timeout strategy.A proper sampled flow timeout can reduce the probability of flow joined and flow divided,and also can enhance the estimating accuracy.We do experiments by using traces collected CERNET.The experiments show that the number of the flow joined and flow divided decreases when we adopt our timeout,the flow distribution can be obtained accurately by using this timeout.