Abstract—Using a uniquemonitoring experiment, we capture all

packets crossing a (lightly utilized) operational access router from

a Tier-1 provider, and use them to provide a detailed examination

of router congestion and packet delays. The complete capture en-

ables not just statistics as seen from outside the router, but also

an accurate physical router model to be identifi ed. This enables

a comprehensive examination of congestion and delay from three

points of view: the understanding of origins, measurement, and re-

porting. Our study defi nes new methodologies and metrics. In par-

ticular, the traffi c reporting enables a rich descr iption of the diver-

sity of microcongestion behavior, without model assumptions, and

at achievable computational cost.

Index Terms—