Abstract The exploding Internet has brought many novel network applications. These include teleconferencing, interactive games, the voice/video phone, real-time multimedia playing, distributed computing, web casting, and so on. One of the specific characteristics of these applications is that all involve interactions among multiple members in a single session. Unlike the traditional one-to-one message transmission (unicasting), if the underlying networks provide no suitable protocol supports, these applications may be costly and infeasible to implement. Multicasting is one technique proposed to efficiently distribute datagrams to a set of interested group members on the interconnected networks. In this article, we survey the multicast routing protocols on the Internet today. Four well-known multicast routing protocols, Distance Vector Multicast Routing Protocol (DVMRP), Multicast extensions to OSPF (MOSPF), Core Based Tree multicast routing protocol (CBT), and Protocol Independent Multicast routing protocol (PIM), are introduced. Different protocols have different design concepts and use different techniques to delivery datagrams and each has its special functions and properties. We provide a succinct explanation of their features. The advantages and weaknesses of these Internet protocols are also examined and compared in detail by several protocol characteristics.