Telepresentations and Scalable Reliable Multicast

Friday, October 31, 1997
10 am
Interschool laboratory (CEPSR)

Jim Gemmell

Jim Gemmell is a researcher in Microsoft's Telepresence Research Group - a part of the Bay Area Research Center (BARC) in San Francisco. Dr. Gemmell received his Ph.D. and B.Sc. from Simon Fraser University and his M. Math from University of Waterloo (both in computer science). His research interests include telepresence, digital audio and video storage and retrieval, and reliable multicast.


Reliable multicast schemes often cannot scale to large receiver sets due to the problems of state explosion and message implosion. In this talk, Erasure Correcting Scalable Reliable Multicast (ECSRM) will be described. ECSRM is based on the SRM framework proposed by Floyd et. al., which utilizes NACK suppression to reduce message implosion. ECSRM makes a number of modifications to SRM to addressed enhanced scalability and rate control. Most notably, instead of re-sending lost packets, erasure-correcting encoded packets are sent in response to NACK messages.

The motivation for ECSRM is telepresentations. A multicast research prototype of PowerPoint transmits data that changes throughout the session using ECSRM, and transmits session persistant data with an FEC-only scheme.

Last modified: 1997-09-01 by Henning Schulzrinne