Abstract: Segment dropping is a novel contention resolution proposed recently. Firstly, the drawback of tail-dropping contention resolution is analyzed in this paper. Then a mod-ified head-dropping policy is proposed. This policy drops the head of contending burst only if the overlapping region of the two bursts is less than the whole contending burst size, oth-erwise drops the whole contending burst. In order to have a better support of differentiated service and alleviate the disorder resulted from head-dropping, a new burst assembly scheme, priority-based mixed burst assembly, is proposed. Such a burst consists of several classes segments, each of which is composed of one or several same class packets and separate head information. The priority of segments is arranged in ascending order in a burst from head to tail. Simulation results show that the proposed scheme performs very well in terms of performance metrics such as the packet loss probability and differentiated services.