A Long-Term Analysis of Growth and Usage Patterns in the Multicast Backbone (MBone)

The Multicast Backbone (MBone), the Internet's multicast research infrastructure, has existed since the early 1990s. Since its inception, there have been few formal studies investigating the “state of multicast”, i.e. the success of multicast deployment. Our work attempts to understand (1) how the MBone is used, (2) how multicast deployment has progressed, and (3) what barriers exist for the continued deployment of multicast. Future research and deployment efforts would benefit significantly with answers to these macro-scale questions. Our work is based on data sets collected over a 4.5 year period. These data sets include join/leave statistics for many of the MBone sessions advertised through the MBone's session directory tool. Using this data, we examine characteristics about the number and frequency of multicast groups and about the users participating in these groups. In addition, we attempt to qualify the accuracy of our results by examining other sources of multicast traffic statistics. Among our conclusions, we find that the use and deployment of multicast has continued to grow, but at a relatively slow rate. Furthermore, most of the activity in the MBone occurs among a relatively small group of core users. Finally, in an attempt to understand why these conditions exist, we offer several possible reasons why multicast deployment has not been more rapid.