The main issues of the next generation Internet are high performance multicast, security and QoS (Quality of Service). The network layer multicast is accepted as a powerful solution to reduce communication overhead in networks as well as hosts. Although a lot of multicast routing protocols have been developed and have worked for the current Internet, they have drawbacks in scalability, reliability and network load balancing. In this paper, we propose an enhanced multicast routing protocol called DCBT (Decentralized Core based Tree), which includes some features of CBT (Core Based Tree), PIM-SM (Protocol Independent Multicast-Sparse Mode) and BGMP (Border Gateway Multicast Protocol). Fundamentally DCBT differs from those in that it covers not only intra-region but also inter-region multicast. RNs (Regional networks) have their intra-region shared trees, which are interconnected by an inter-region shared tree for a multicast group. New two concepts are introduced: the one is RBTS (Region Based Tree Switching) to achieve network load balancing and the other is to redefine TOS (Type Of Service) byte to make special multicast routing decision. In addition, the effect of core location is given by changing its position within an RN. Finally we provide the performance evaluation of DCBT by OPNET network simulator over a real scale network model.