The packet pair/train technique estimates the capacity bottleneck of a path from the dispersion experienced by two/multiple back-to-back packets.This paper analyzes the measured noise and explains the distributions of measured samples under different probing packet sizes and different packet train lengths.Based on the noise analysis and a 'signal model’

a new algorithm called MBFA (Model-Based Filtering Algorithm) is presented

which uses 'signal model’ to enlarge the signal and to eliminate the noise.