NetFlow是流测量中广泛应用的解决方案,但NetFlow的抽样方法存在一定的缺陷:泛洪攻击时消耗路由器过多的资源;用户很难选择适合所有流量组成情况的静态抽样率,以平衡资源消耗量和准确率.提出了一种易于实现的分组抽样方法.该方法利用测量缓冲区对定长时间内到达的分组进行固定数量的抽样,既可以使抽样率自适应于流量变化,又可以控制资源的消耗.证明了抽样估计的无偏性,并推导出估计值相对标准差的理论上界.实验结果表明,与已有方法相比,该方法在具有简单性、自适应性及资源可控性的同时不会失去准确性.

Although NetFlow is widely deployed for traffic measurement, the sampling method of Netflow has shortcomings: it consumes excessive router resource during flooding attacks; selecting a suitable static sampling rate is difficult because no single rate gives the right tradeoff between resource consumption and accuracy for all traffic mixes. An easily-implemented packet sampling method is presented in this paper, which samples a fixed number of packets in the constant period with measurement buffer. The method can automatically adapt the sampling rate to traffic variety and provide the controllability of resource consumption. Theoretical analyses demonstrate that the new method can provide unbiased estimation with certain relative standard deviation bound. Experiments are also conducted with the real network traces. Results show that the proposed method can achieve simplicity, adaptability and controllability of resource consumption without sacrificing accuracy compared with other sampling methods.

Supported by the National Natural Science Foundation of China under Grant Nos.90604019, 60472067, 60502037 (国家自然科学基金); the National Grand Fundamental Research 973 Program of China under Grant Nos.2003CB314806, 2006CB701306 (国家重点基础研究发展规划(973)); the China Next Generation Internet Project under Grant No.CNGI-04-8-1D (国家CNGI项目)