关键词: 时钟倾斜, 网络测量, 多媒体协同

Abstract: Clock skew shifts one-way delay measure result.It leads to poor QoS of multimedia collaboration.An accurate skew estimate will help to compensate the effect of skew.In this paper，a less error skew estimate algorithm is introduced which is based on simultaneous measure to multiple nodes.Firstly，a random estimate，which could be used to calculate relative skew between each node，is given to each node.Finally，the estimations are optimized by comparing calculated relative skew to measured one.In one word，measuring of skew is transformed to optimizing problem on distance function of calculated and measured skew.It was proved that the result of optimum problem is unbiased；error is less than error of point to point styled measure.The applications on real Internet show that this algorithm is accurate and stable，furthermore it is fast enough for real-time process.

Key words: clock skew, network measurement, multimedia collaboration