In previous years, the Internet using a conventional IP mechanism had a lot of problems such as slow packet forwarding, complex routing and inefficient usage of network resources. Multi-Protocol Label Switching (MPLS) is one of the mechanisms that are proposed to solve these problems. In addition, multicast is one of the big issues in the Internet society because it can efficiently support real-time multimedia traffic. Therefore, the next generation Internet will be a system which have an MPLS backbone and can support multicast. An MPLS multicast mechanism is considered under Internet broadcasting systems. Specially, the scalability problem of common problems in MPLS and multicast is solved using label aggregation. In the proposed algorithm, the Label Edge Router (LER) of edge router in MPLS has a new table containing information of each tree node. The table is called the multicast Tree Node Table. Extending the Constraint-based Routed Label Distribution Protocol (CR-LDP), the label allocation is performed by using this table. The scalability problem can be solved using this algorithm because it reduces label consumption. So, the MPLS multicast mechanism can be easily supported in a large Internet backbone network.