Toronto Networking Seminar

Organized by Department of Computer Science and Department of Electrical and Computer Engineering, University of Toronto

On the Stability and Optimality of Universal Swarms

Stratis Ioannidis
Technicolor Research Lab Palo Alto, CA, USA

Date: Monday, Nov. 14, 4:10-5:00pm
Location: BA7231 (Bahen Centre)


Recent work on BitTorrent swarms has demonstrated that a bandwidth bottleneck at the seed can lead to the underutilization of the aggregate swarm capacity. Bandwidth underutilization also occurs naturally in mobile peer-to-peer swarms, as a mobile peer may not always be within the range of peers storing the content it desires. We argue that, in both cases, idle bandwidth can be exploited to allow content sharing across multiple swarms, thereby forming a universal swarm system. We propose a model for universal swarms that applies to a variety of peer-to-peer environments, both mobile and online. Through a fluid limit analysis, we demonstrate that universal swarms have significantly improved stability properties compared to individually autonomous swarms. In addition, by studying a swarm's stationary behavior, we identify content replication ratios across different swarms that minimize the average sojourn time in the system. We then propose a content exchange scheme between peers that leads to these optimal replication ratios, and study its convergence numerically.


Stratis Ioannidis is a researcher at Technicolor in Palo Alto, CA. He received an M.Sc. (2004) and a Ph.D. (2009) in Computer Science from the University of Toronto, Canada, and a B.Sc. (2002) in Electrical and Computer Engineering from the National Technical University of Athens, Greece. Between 2009 and 2011, he worked as a postdoctoral researcher at Technicolor in Paris, France.