Recently, audio and video delivery services are widely spread in the Internet. In order to deliver these data to multiple receivers at the same time, the multicast technologies are indispensable. In such a situation, the performance analysis of multicast traffic will be important in order to design and operate the Internet. Multicast traffic is controlled by its own routing protocol and the multicast routing protocol is more complex than conventional unicast routing protocols. In this paper, we propose a new multicast performance analyzer considering DVMRP and PIM-SM routing protocols. It captures messages of a multicast routing protocol as well as multicast IP datagrams. It also analyzes DVMRP and PIM-SM messages in order to investigate the behaviors of multicast IP datagrams and measures the statistics of multicast traffic in detail. This paper describes the detailed design of the multicast performance analyzer and the results of analyzing multicast datagrams transmitted over networ...