This paper presents architecture and mechanisms to support multiple QoS under the DiffServ paradigm. On the data plane, we present a node architecture based on the virtual time reference system (VTRS), which is a unifying scheduling framework for scalable support of the guaranteed service. The key building block of our node architecture is the core-stateless virtual clock (CSVC) scheduling algorithm, which, in terms of providing delay guarantee, has the same expressive power as a stateful weighted fair queueing (WFQ) scheduler. Based on the CSVC scheduler, we design a node architecture that is capable of supporting integrated transport of the guaranteed service (GS), the premium service (PS), the assured service (AS), and the traditional best-effort (BE) service. On the control plane, we present a BB architecture to provide flexible resource allocation and QoS provisioning. Simulation results demonstrate that our architecture and mechanisms can provide scalable and flexible transport of integrated traffi c of the GS, the PS, the AS, and the BE services.