Using Tree Topology for Multicast Congestion Control

Srinivasan Jagannathan, and  Kevin C. Almeroth
Department of Computer Science
University of California
Santa Barbara, CA 93106-5110
{jsrini, almeroth}@cs.ucsb.edu

Multicast is a promising technique for mass distribution of streaming media.
However, the inherent heterogeneity of the Internet poses several challenges. A
major challenge is to develop a congestion control mechanism that is efficient,
flexible (to administrative heterogeneity) and deployable. Many approaches using a
layered encoding scheme have been proposed to address this problem. In parallel,
many tools are being developed which provide a snapshot of network internals. Of
particular interest are multicast topology discovery tools. The existence of such
tools motivates the possibility of using tree topology information for multicast
congestion control. In this paper we seek to understand the benefits of such a
mechanism and the challenges in its practical implementation. We develop an
algorithm, called TopoSense, which uses topology information and layered streams to
control congestion within an administrative domain. Our algorithm presents a new
model for multicast congestion control as it does not involve on-router computation
as opposed to other approaches which require router support. We evaluate our
algorithm using ns, the network simulator. Our results indicate that topology
information is very useful in understanding the dynamics of multicast congestion and
can be used for efficient traffic management.

Keywords:   Congestion Control, Layered Multicast, Tree Topology