In this paper we propose a scalable differentiated service model paradigm to provide fine QoS granularity in Internet via the framework of a distributed admission control scheme referred to as Explicit Endpoint Admission Control (EEAC). Specifically, in the proposed EEAC scheme the end host sends out probing packet to the network and makes admission decision according to the probing results that are explicitly provided at each router along the path. By introducing the concept of service vector, the proposed service model paradigm allows users to choose different services at different nodes along the path from the source to the destination to achieve fine QoS granularity and architectural scalability. Models for both users and network service providers to maximize their benefits are also discussed in this paper. The corresponding simulation results demonstrate that the new service model paradigm and EEAC scheme can result in lower request drop ratio, satisfactory end-to-end performance, and lower cost for each user.