Clock synchronization is a crucial issue for scalable and accurate network performance measurements, especially when no external time sources are introduced. The paper presents a clustering based efficient and robust algorithm Optimized Top-Down Time series Segmentation (OTDTS) for clock synchronization between end-to-end systems. The computational complexity of OTDTS is of order OðKN2Þ. Based on the one-way probe delay traces, the algorithm segments the delay time series at proper points, at which clock dynamics occur. End systems could achieve relative clock synchronization by estimating and removing the clock skew of each segment. Simulations on artificial data set and practical Internet measurement illustrate the availability and efficiency of OTDTS.

网络被动测量技术是网络测量研究的一个重要方面。讨论了测量系统中数据包的抽样捕获算法和包头压缩方法，并给出了一个被动测量系统组成结构和主要功能模块的设计，并阐述了测量探针与控制主机的通信机制。

Collecting network traffic is becoming a more challenging task in passive network measurement due to the rapid growth of link speed. Flow-based network traffic capture and storage provides an efficient way for high-speed network measurement. The paper concentrates on the flow detection issue which is also the premise for further flow-based traffic analysis and modeling in such challenging environment. Based on the statistical investigation of the correlations between flow size and the maximum packet interarrival time within a flow, we obtain the empirical conditional distribution functions for some popular TCP protocol-based application flows, and then propose a Probability-Guaranteed Adaptive Timeout algorithm (PGAT) for flow termination decision. The assessment criteria for flow termination decision algorithm is systematically developed. Comparisons on flow generation ratio, flow intact ratio, and mean flow extra retaining time metrics indicate that the PGAT algorithm can obtain more attractive performance than other related works.