12:45 PM, February 8, 2001
Gates Building, Room 104

Scattercast--Taming IP Multicast
An Architecture for Internet Broadcast Distribution as an Infrastructure Service

Yatin Chawathe,
AT&T Labs Research

About the talk:

Despite the phenomenal success of the world wide web, one class of Internet applications that has yet to be satisfactorily realized is that of Internet broadcasting--the distribution of Internet content from one or more sources to a large number of simultaneous receivers. The traditional solution for this problem, IP multicast, has met with limited success due to a number of factors including manageability, lack of robust inter-domain multicast routing, scalability, and heterogeneity. Hence, rather than relying on the existence of a globally deployed multicast backbone, we propose a new model for Internet broadcasting where we view multi-point delivery not as a network primitive but rather as an application-level infrastructure service. Our architecture relies on a collection of strategically placed network agents that collaboratively form an overlay network of unicast interconnections on top of which a source distributes data to its receivers. Clients locate a nearby agent and tap into the session via that agent. This model effectively partitions the client set into a number of small data groups interconnected by robust unicast links. We call this communication model scattercast and the network agents that are central to this model ScatterCast proXies or SCXs.

We address two key challenges that arise out of such an infrastructural approach. First, to form an efficient overlay network of SCXs, we developed a protocol called Gossamer that groups clients with SCXs and builds a distribution network composed of unicast connections across SCXs. Second, to allow applications to distribute data on top of this overlay in a manner that is optimized for the specific application and end-user environments, scattercast develops a highly flexible and application-aware transport framework that incorporates the semantics of the application data into the transport protocol. We believe that this approach of explicit application-level infrastructure embedded within the network is a new and promising direction for adaptive Internet applications such as network broadcasting. In the future, we expect to see a greater proliferation of such infrastructural elements that enhance the Internet's capabilities while at the same time co-existing with the core IP architecture.

About the speaker:

Yatin Chawathe received a Bachelors degrees in Computer Engineering from the University of Bombay in 1995 and a Masters and PhD in Computer Science from the University of California at Berkeley in 1998 and 2000, respectively. At Berkeley, Yatin was a member of the BARWAN and MASH research groups and he participated in a variety of Internet Systems research projects. His PhD thesis developed the Scattercast architecture to support Internet broadcast distribution. Yatin joined the Internetworking Research Department at AT&T Labs in Menlo Park in October, 2000. His current research interests include Internet broadcasting and infrastructure services.

For more information:

Powerpoint slides