A relative time model in a distributed network using exchanged time information

In a distributed network, a great number of network applications, such as measurements of one-way delay, can be performed by measuring accurately synchronized clocks from different network computers. Due to the difference of frequency and time between different clocks, these clocks are not synchronized, so in one-way delay measurements between two computers there exists a relative time offset. S.B. Moon et al. (see Proc. INET 2000) and V. Paxson (see PhD Dissertation, U.C. Berkeley, 1997; Proc. ACM SIGMETRICS, p.11-21, 1998) directly analyze one-way delay measurements to remove measurement error. In our approach, the frequency and time information between computers´ clocks is exchanged, and a relative clock model between two computer clocks can be established; based on the relative clock model, the measured delay timestamp is corrected, and so the one-way delay measurement is also corrected indirectly. Two groups of measured data in a local area network, and one group of one-way delay between Southeast University in China and AMS in Switzerland are analyzed to verify the relative clock model. The result shows that the relative clock model can describe the relative relationship between different computer clocks, and correct the measured error of one-way delay between computers.