In this paper, we propose two techniques supporting differentiated service for different priority packets, Differentiated Fair ID Countdown (DFIC) and Controllable Fair ID Countdown (CFIC). DFIC supports absolute service differentiation among classes through the use of an explicit priority segment, while CFIC achieves prioritized access through assigning different waiting times for nodes to access the medium. Both of DFIC and CFIC can achieve the fairness among nodes of same priority group. CFIC also achieves controllable relative throughout differentiation among different priority levels and can guarantee starvation-free access for all nodes.