A Tool for Debugging Internet Multicast

In this paper we describe a debugging tool that is an eeective means of analyzing problems with multicast packet routing in a network. Multicast packet routing is a source-driven distributed calculation performed by the routers in a multicast network. The routes taken by multicast packets are diicult to predict manually due to the large number of variables that must be considered. The multicast route debugging tool allows oo-line investigation of the route taken by a multi-cast packet and the eeects of network modiications on that route. The tool has already proved useful in debugging the problems that have occurred in the experimental Internet Multicast Backbone. The multi-cast route debugging tool currently predicts multicast routes of packets using the distance-vector truncated-broadcast algorithm implemented for Internet multi-cast traac. We will be upgrading the tool to allow the user to choose other multicast routing algorithms. 1