vrsyrotiuk@water.waterloo.edu (Violet Syrotiuk) (04/03/89)
DEPARTMENT OF COMPUTER SCIENCE UNIVERSITY OF WATERLOO SEMINAR ACTIVITIES COMPUTER NETWORKS SEMINAR - Thursday, April 6, 1989 Mr. Peter B. Danzig, of the University of California at Berkeley, will speak on ``Making Multicast Fast''. TIME: 3:30 PM ROOM: DC 1304 ABSTRACT When many or all of the recipients of a multicast message respond to the multicast's sender, their responses may overflow the sender's available buffer space. Buffer overflow is a serious, known problem of broadcast-based protocols, and can be troublesome when as few as three or four recipients respond. We develop analytical models and techniques that calculate the distribution of the number of buffer overflows, and we apply these techniques to make multicast with limited buffers fast. The common cure for buffer overflow requires that recipients delay their responses by some random amount of time in order to increase the minimum spacing between response messages, eliminate collisions on the network, and decrease the peak processing demand at the sender. In our table driven algorithm, the sender minimizes the multicast's expected latency, the elapsed time between its initial transmission of the multicast and its reception of the final response, given the number of times (rounds) it is willing to retransmit the multicast. We apply our analytical results to optimally select each round's timeout. We demonstrate that multiple round multicasts can be an order of magnitude faster than single round multicasts. We will discuss these results and our experience with a small prototype multicast system. -- Violet R. Syrotiuk | vrsyrotiuk@water.uucp Computer Science Dept. | watmath!water!vrsyrotiuk University of Waterloo | vrsyrotiuk@water.uwaterloo.ca Waterloo, ON N2L 3G1 | vrsyrotiuk@water.waterloo.edu (or .cdn)