This paper proposes COPP

i.e.chirp of packet pairs

a novel active method to yield available bandwidth along network paths.The probes in COPP are composed of several chirps of packet pairs

e.g.several trains of packet pairs where the interval between the first and the second packet within packet pair is gradually decreased.For each chirp of packet pairs traversed the measured path

we find out all turning points in the chirp

and then give them distinct weight in the final available bandwidth calculation according to the degree of experienced distortion.The turning point is such a packet pair that is disturbed more obviously by cross traffic in contrast to its neighbor pairs.Two rules are developed to determine whether a packet pair is a turning point or not.Additionally

COPP can determine its estimate bound dynamically by exploiting the bandwidth requirements of concrete applications if known.We also inspect the selection of the probe packet size in COPP through simulations.Finally

comparisons between COPP and other measurement tools such as Pathload and Spruce show that COPP is an agile and stable technique and can provide relatively higher accurate results with fewer overheads.