Clock skews of devices on the Internet are viewed as one way delay noise, but their distribution is unknown. The authors explore the distribution of clock skews to see the conflict probability. In this paper, they introduce an accurate clock skew estimation algorithm to filter inaccurate clock skew estimation by comparing the results between linear programming method and least square fitting. Delay jitter and other noises affect the estimation result. When the difference of two methods is large, the estimation result is unstable and inaccurate, so the estimation result should be dropped.