A low overhead

self adaptive method for end-to-end available bandwidth estimation was proposed. Firstly

on low utilization path

the mathematic equation between the probability that input probe gap increases caused by CT pack-ets and the distribution of output probe gap was set up

and then CT load was derived from the equation. Secondly

a met-ric called gap symmetry （GS） was proposed to weigh the busyness degree of a network path

and the self adaptive avail-able bandwidth estimation method based on GS was presented. NS-2 simulations show that compared with previous methods

our method shows its advantages in terms of measurement time

accuracy

and overhead.