WitMeMo’06 Schedule

August 5th, 2005

 

9am-9:15am Welcome

           

 9:15am-10am Keynote Speech

 

802.11 in the Large: Observations at an IETF meeting

Prof. Henning Schulzrinne

 Columbia University

Authors : Andrea Forte, Sangho Shin, Henning Schulzrinne

Abstract : We observed wireless network traffic at the 65th IETF Meeting in Dallas, Texas in March of 2006, attended by approximately  1200 engineers.  The event was supported by a very large number of 802.11a and 802.11b access points, often seeing hundreds of simultaneous users.  We were particularly interested in the stability of wireless connectivity, load balancing and loss behavior, rather than just traffic. We observed distinct differences among client implementations and saw a number of factors that made the overall system less than optimal, pointing to the need for better design tools and automated adaptation mechanisms.

 

Prof.  Henning Schulzrinne received degrees from Darmstadt (Germany) University of Technology, the University of Incinnati and the 
University of Massachusetts in Amherst.  He has held research positions at GMD Fokus, Berlin and Bell Laboratories before joining the 
faculty of Columbia University, New York.  He is currently chairing the Department of  Computer Science.  His research interests 
encompass real-time network services, ubiquitous and mobile computing and network reliability.  He is a co-author of numerous RFCs, 
including RTP, RTSP, SIP and GIMPS.

 

 

10-10:30am Invited Talk

The Exploration of a Bus Based Delay Tolerant Network

Ellen (Xiaolan)  Zhang

University of Massachusetts Amherst

Abstract : In this work, we study mobility traces collected from UMassDieselNet, an operational Delay Tolerant Network made up of 30 buses covering an area of approximately 150 square miles. Each bus, equipped with a brick computer, a 802.11b access point and interface, scans for surrounding access points and transfers the largest amount of data possible on discovering a bus within contact range. The starting time, duration and amount of data transferred at each contact are logged. To study the feasibility and performance of data forwarding schemes under such network, we analyze an eighty day long trace collected in the spring of 2006. We statistically characterize the meeting processes among buses, taking into account the heterogeneity of meeting processes for different pairs. In order to reduce model parameters, we explore algorithms for clustering nodes with similar meeting processes. We also characterize the trace using a graph model, including studying the degree structure of the resulting contact graph and calculating various metrics of the temporal network.

Xiaolan Zhang received a bachelor's degree in computer science from Peking University of China, and a master degree in computer science from University of Massachusetts, Amherst. She is currently a Ph.D. candidate at the Computer Science Department at University of Massachusetts, Amherst, co-advised by Prof. Don Towsley and Jim Kurose. Her research interests include wireless mobile network, including Delay Tolerant Network, multimedia communication, network measurement, and modeling and performance evaluation.

 

 

10:30am-11am: Coffee Break

 

 

11-11:30am: Invited Talk

On the Interaction between TCP and the Wireless Channel in CDMA2000 Networks

Prof. Azer Bestavros

Karim Mattar

Boston University

Boston University

Authors : Karim Mattar, Ashwin Sridharan, Hui Zang, Ibrahim Matta and Azer Bestavros

Abstract : In this work, we conducted extensive active measurements on a large nationwide CDMA2000 1xRTT network in order to characterize the impact of both the Radio Link Protocol and more importantly, the wireless scheduler, on TCP. Our measurements include standard TCP/UDP logs, as well as detailed RF layer statistics that allow observability into RF dynamics. With the help of a robust correlation measure, normalized mutual information, we were able to quantify the impact of these two RF factors on TCP performance metrics such as the round trip time, packet loss rate, instantaneous throughput etc. We show that the variable channel rate has the larger impact on TCP behavior when compared to the Radio Link Protocol. Furthermore, we expose and rank the factors that influence the assigned channel rate itself and in particular, demonstrate the sensitivity of the wireless scheduler to the data sending rate. Thus, TCP is adapting its rate to match the available network capacity, while the rate allocated by the wireless scheduler is influenced by the sender's behavior. Such a system is best described as a closed loop system with two feedback controllers, the TCP controller and the wireless scheduler, each one affecting the other's decisions. In this work, we take the first steps in characterizing such a system in a realistic environment.

Azer Bestavros (PhD'92, Harvard U) is Professor and Chairman of the Computer Science Department at Boston University, which he joined in 1991. Prof. Bestavros' research interests are in the general areas of networking and real-time systems. Prof. Bestavros' networking research aims at improving the scalability of Web and Internet services as reflected in his pioneering of the content distribution model adopted years later by CDNs, his work on traffic self similarity and reference locality characterization, his work on various caching and streaming media delivery protocols, his work on end-to-end inference of network caricatures, and his work on identifying and countering adversarial exploits of system and network dynamics. Prof. Bestavros' real-time systems research revolves around improving service predictability and QoS as exemplified in his generalization of  classical rate-monotonic analysis to accommodate uncertainties in resource availability/usage, his use of redundancy-injecting codes for timely access to periodic broadcasts, and his work on virtualization services for embedded sensor networks.

Karim Mattar is a PhD student at the Computer Science Department at Boston University, working under the supervision of Professors Azer Bestavros and Ibrahim Matta. Since 2005, Karim has been collaborating with researchers at Sprint Labs on the characterization CDMA wireless networks, and studying the impact of both the Radio Link Protocol and the wireless scheduler on transport protocols. Karim's broader research interests include network tomography, protocol design, network security, traffic engineering, and sensor networks. Karim graduated from the University of Massachusetts in Amherst with a bachelor's degree in Computer Systems Engineering, and a minor in Computer Science, in May 2003.

 

 

 

11:30am-12:15pm: Regular Paper Presentations

 

*       Impact of Interference and Capture Effects in 802.11 Wireless Networks on TCP

Vijaynarayanan Subramanian

K.K. Ramakrishnan

Shiv Kalyanaraman

Lusheng Ji

 

RPI

AT&T Labs

 

RPI

 

AT&T Labs

 

*       Identifying, Characterizing, and Controlling Stealth Worms in Wireless Networks Through Biological Epidemiology

Kristopher Hall,

Randy Marchany,

Nathaniel Davis

Virginia Tech

Virginia Tech

Air Force Institute of Technology

 

 

 

 

 

12:15pm: Lunch