一种测量任意链路可用带宽的方法

Methodology for Measuring Available Bandwidth on Arbitrary Links

可用带宽测量对于网络行为分析、网络服务质量(quality of service,简称QoS)的验证等有很重要的作用.现有可用带宽测量工作主要集中在端到端路径可用带宽测量,仅提供路径上承压链路(tight link)的信息,而不能提供其他关键链路的信息.为此,提出一种新颖的链路可用带宽测量算法LinkPPQ(trains of pairs of packet-quartets used to measure available bandwidth of arbitrary links),它采用由四探测分组结构对构成的探测序列,能够测量网络中任意链路的可用带宽,并跟踪该链路上背景流的变化.在仿真环境和实际网络环境下研究了LinkPPQ的性能.仿真结果表明,在几种不同背景流场景下,对于具有单狭窄链路的路径和具有多狭窄链路的路径,LinkPPQ都能够对各个链路的可用带宽进行有效的测量.绝大多数情况下测量误差小于30%,且具有较好的测量平稳性.实验网的实验结果也表明,LinkPPQ可以准确测量以下几种情况下的链路的可用带宽:a)从容量为10Mbps的链路准确地测量一条100Mbps链路的可用带宽;b)准确测量容量10倍于紧邻其后狭窄链路的容量的链路的可用带宽;c)准确测量具有多狭窄链路的路径上各狭窄链路的可用带宽.

The available bandwidth measurement is important for many Internet applications, such as network behavior analysis, quality of service （QoS） verification, and so on. Existing available bandwidth measurement tools mainly measure the available bandwidth for a whole network path, and provide information about the tight link（s） other than vital links. Therefore, this paper presents a novel algorithm called LinkPPQ （trains of pairs of packet-quartets used to measure available bandwidth of arbitrary links）, which uses trains of pairs of packet-quartets to measure the available bandwidth of any link along the path, and track the variety of the cross-traffic on it. This paper studies the performance of LinkPPQ in both simulation circumstances and the laboratorial network. Simulation results show that LinkPPQ can accurately measure the available bandwidth of each link on the paths that have one narrow link or multiple narrow links, under different cross-traffic loads. Most measurement errors are under 30%, and the results are stable. The laboratorial experimental results show that LinkPPQ can accurately measure the available bandwidth in the following situations： a） measuring a link with capacity lOOMbps from a link with capacity lOMbps; b） monitoring the link with capacity that is ten times of the narrow link next to it on the path; c） estimating the available bandwidth of the narrow links on a path having multiple narrow links.