This paper presents the Differentiated Services (DiffServ) over ATM based Multiprotocol Label Switching (MPLS) core network architecture. This network supports the Integrated Services (IntServ) as well as DiffServ through ATM shortcut connection or MPLS label swapping using flow-based admission control to realize Quality of Service (QoS). In this paper, we discuss a DiffServ mapping and integrated packet scheduler. Also we propose the flow-based traffic admission control algorithm that is suitable for multiple service classes. This algorithm can be achieved two objects which are reliable delay bounded QoS provisioning and high resource utilization. This algorithm reduces the reject probability of high priority service class flow in operating DiffServ. The proposed approaches guarantee a hard QoS using ATM shortcut connection for IntServ guaranteed service class and increase resource utilization according to per class QoS condition for other service classes. ATM shortcut has many advan...