Abstract: The available bandwidth measurement is important for many Internet applications，such as server selection，overlay network routing，and traffic engineering.This paper analyzes the relationship of the probing rate and the one-way delays.Then based on this，a methodology which call PFAB（polynomial fitting for available bandwidth） in the basic idea from polynomial fitting is presented to measure end-to-end available bandwidth.In PFAB，the change of the one-way delay happen according to one-way delay trends to infer the relationship between the probing rate and the available bandwidth.If one-way delay is increasing，the probing rate is larger than the present available bandwidth;if one-way delay is not increasing，the probing rate is equals the present available bandwidth;otherwise，one-way delay is decreasing.This methodology can reduce the number of probe bytes，the time of probing and network interference through NS-2 simulations.It also can find out extreme point with lowing measurement errors when probing rate has a big change.

Key words: available bandwidth, polynomial fitting, probe rate model, bandwidth measurement

摘要： 有效带宽测量在服务器选择、覆盖网络路由选择和网络流量工程等方面有广泛的应用。通过分析发送频率与单向延时之间的关系，提出了一种基于多项式拟合的有效带宽测量方法PFAB（Polynomial Fitting for Available Bandwidth）。PFAB通过发送探测速率逐渐下降的探测包，并检测OWD的变化，推断探测速率和有效带宽之间的关系。当探测速率大于有效带宽时，OWD持续增长;在探测速率等于有效带宽时，OWD达到最大值，之后开始下降。NS-2仿真实验结果表明该方法能有效减少探测包数量，缩短探测时间，并且对网络造成的干扰小;在探测包瞬时频率变化较大时，可以快速到极值点，减少测量误差。

关键词: 有效带宽, 多项式拟合, 报文速率模型（PRM）, 带宽测量