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In network measurement, one-way delay is an important network performance indicators, during the measurement, to synchronize the time of different nodes has a great influence on the results of measurement, especially in the large-scale network measurement. This paper propose a time synchronization stability comparison method based on NTP after research the time synchronization technology. In the one-way delay measurement, in order to eliminate measurement errors caused by the frequency difference between nodes, this paper propose a one-way delay corrective algorithm based on forward and reverse delay measurement after research existing time corrective algorithm. Finally, the measurement platform deployed in Planetlab and measure one-way delay. The measurement select more stable nodes based on NTP stability comparison algorithm, and correct one-way delay measurement results through clock corrective algorithm mentioned above. Experiments show that the results of corrective measurement algorithm are more accurate.

The current network emulators commonly have bad versatility and their emulation fidelity is not high. Based on the principle of network emulation, this essay designs and implements a network path quality indicators emulation system, which can be transparently series deployed on a network path and change the performance of this path. The main tasks are: achieves a "Transparent Bridge" on Windows platform, using WinPcap packet capturer, gives the quality indicators emulation algorithms and models, studies the relationships between the indicators of network quality and the emulation algorithms has been improved and optimized based on this, designs, implements and verifies the emulation system. The emulation system has good cross-platform features, it achieves the frame-level emulation in the link layer, so it has a high fidelity.