Summary: IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 11, NO. 1, FEBRUARY 2003 153
On the Topology of Multicast Trees
Robert C. Chalmers, Student Member, IEEE, and Kevin C. Almeroth, Member, IEEE
Abstract--The benefit derived from using multicast is seemingly
dependent upon the shape of the distribution tree. In this paper,
we attempt to accurately model interdomain multicast trees. We
measure a number of key parameters, such as depth, degree
frequency, and average degree, for a number of real and synthetic
data sets. We find that interdomain multicast trees actually do
share a common shape at both the router and autonomous system
levels. Furthermore, we develop a characterization of multicast
efficiency which reveals that group sizes as small as 20 to 40
receivers offer a 55%70% reduction in the total number of links
traversed when compared to separately delivered unicast streams.
A final contribution of our work consists of a number of data sets,
compiled from multicast group membership and path data, that
can be used to generate large sample trees, representative of the
current multicast infrastructure.
Index Terms--Efficiency, modeling, multicast, topology.