Dr. Jörg Liebeherr

(University of Toronto)

"Getting a Grip on Delays in Packet Networks"

A delay analysis for packet network is notoriously hard. Statistical properties of traffic, link scheduling, and subtle correlations between traffic at different nodes increase the difficulty of characterizing the variable portion of delays. This talk discusses recent progress on the end-to-end delay analysis for a traffic flow in a packet network, using a stochastic network calculus analysis approach. We seek answers to the following questions: What is the relative impact of scheduling and statistical multiplexing on determining delays at a packet switch?

What are the scaling properties of end-to-end delays as the number of traversed switches is increased? Does the impact of packet scheduling algorithms diminish when network paths grow large? A key finding is that delays of a flow traversing a sequence of nodes and experiencing cross traffic at each node scale faster than linearly in the number of nodes, when traffic dos not satisfy independence assumptions. More precisely, for exponentially bounded packetized traffic, delays are shown to grow with O(H log H), where H is the number of nodes on the network path. This superlinear scaling of delays is qualitatively different from the scaling behavior predicted by a worst-case analysis or by a probabilistic analysis assuming independence of traffic arrivals.

Bio: Jörg Liebeherr received the Ph.D. degree in Computer Science from the Georgia Institute of Technology in 1991. He is currently with the Department of Electrical and Computer Engineering of the University of Toronto as the Nortel Chair of Network Architecture and Services. He is a Fellow of the IEEE. He served on the Board of Governors of the IEEE Communications Society in 2003-2005, and as chair of the IEEE Communications Society Technical Committee on Computer Communications in 2004-2005. He was Editor-in- Chief of IEEE Network in 1999-2000, and an Associate Editor of IEEE/ACM Transactions on Networking and several other journals. He received an NSF Career award in 1996, a best paper award (as co-author) at ACM Sigmetrics 2005, and an Outstanding Service award from the IEEE ComSoc Technical Committee on Computer Communications in 2006.

Zeit: Montag, 10.06.2013, 17.15 Uhr
Ort: Gebäude 48, Raum 680