12:15PM, Thursday, March 1st 2007.
Gates 104

Router buffer sizing revisited: the role of the output/input capacity ratio.

Constantine Dovrolis
Georgia Institute of Technology

About the talk:
The issue of router buffer sizing is still open and significant. Previous work either considers open-loop traffic, or only analyzes persistent TCP flows. This paper differs in two major ways. First, it considers the more realistic case of non-persistent TCP flows with heavy-tailed size distribution. Second, instead of only looking at link metrics, we focus on the impact of buffer sizing on TCP performance. Through a combination of testbed experiments, simulation, and analysis, we reach the following conclusions. The output/input capacity ratio at a network link largely determines the required buffer size. If that ratio is larger than one, the loss rate drops exponentially with the buffer size and the optimal buffer size is close to zero. Otherwise, if the output/input capacity ratio is lower than one, the loss rate follows a power-law reduction with the buffer size, and significant buffering is needed, especially for flows that are mostly in congestion-avoidance. Smaller transfers, which are mostly in slow-start, require significantly smaller buffers. We conclude by revisiting the ongoing debate on ``small versus large'' buffers from a new perspective.


About the speaker:
Dr. Constantine Dovrolis is an Assistant Professor at the College of Computing of the Georgia Institute of Technology. He received the Computer Engineering degree from the Technical University of Crete (Greece) in 1995, the M.S. degree from the University of Rochester in 1996, and the Ph.D. degree from the University of Wisconsin-Madison in 2000. He was an assistant professor of Computer and Information Science at the University of Delaware from January 2001 to July 2002. His research interests include Internet protocols and technologies, network measurements and their applications, overlay and multi-homed networks, intelligent route control, router buffer sizing, service provisioning and traffic engineering, and biology-inspired network architectures. He received the NSF CAREER award in 2003.