Scalable Techniques for Discovering Multicast Tree Topology

The IP multicast infrastructure has transitioned to a topology that now supports hierarchical routing. Multicast network monitoring and management have become key requirements necessary for providing robust multicast operation. Monitoring services help to identify potential problems such as protocol shortcomings, implementation bugs or configuration errors. This type of monitoring often requires knowing the multicast tree topology. In this paper, we present a new approach, called tracetree, to discover tree topology in the source-to-receiver(s) direction using network forwarding state. We start with an overview of the problem. Then, we describe tracetree functionality including its request forwarding and response collection mechanisms. Next, we discuss a number of functional issues related to tracetree. Finally, we evaluate our technique by comparing it to a number of alternative approaches. We believe that our technique provides a scalable way of discovering a multicast tree’s topology in realtime while requiring only marginal additional router functionality.