Systems Seminar: Jim Kurose, University of Massachusetts

Measurement-in-the-Middle: Classification of Out-of-Sequence Packets in a Tier-1 IP Backbone

Abstract

In this talk, we consider the problem of measuring out-of-sequence packets in TCP connections crossing a tier-1 IP backbone, and characterizing the causes for such out-of-sequence packets.

After presenting a brief overview of current approaches towards network measurement, we describe a new measurement and analysis methodology that we call "measurement-in-the middle," that can be used to characterize performance measures such as packet reordering, loss, and delay along an end-to-end path from measurements taken at a single point on an end-end path. For the case of out-of-sequence packets, we describe techniques to classify the causes of observed out-of-sequence behavior based only on the previously- and subsequently-observed packets within a connection and knowledge of how TCP behaves. Using these simple techniques, we classify and quantify the effects of various causes of observed out-of-sequence packets, including retransmission of lost packets, reordering of packets on the end-end path, and packet duplication in the network. We analyze numerous several-hour packet-level traces from a set of OC-12 and OC-48 links for 14 million connections generated in more than 3,400 unique ASes. Our measurements show a relatively consistent amount of out-of-sequence packets of approximately 5%. We find that few out-of-sequence packets result from pathological problems such as in-network duplication or in-network reordering. We conclude the talk with a discussion of the application of the measurement-in-the-middle approach to other problems in network measurement, analysis, and characterization

This is joint work with Christophe Diot and Gianluca Iannaccone (Sprint) and Sharad Jaiswal and Don Towsley (Univ. Massachusetts)

Speaker Bio

Jim Kurose received a B.A. degree in physics from Wesleyan University and a Ph.D. degree in computer science from Columbia University in 1984. He is currently a professor (and past chairman) in the Department of Computer Science at the University of Massachusetts. His research interests include network protocols and architecture, network measurement, multimedia communication, network and operating system support for servers, and modeling and performance evaluation. He is the past Editor-in-Chief of the IEEE Transactions on Communications and was the founding Editor-in-Chief of the IEEE/ACM Transactions on Networking. He has been active in the program committees for IEEE Infocom, ACM SIGCOMM, and ACM SIGMETRICS conferences for a number of years, and has served as Technical Program Co-Chair for these conferences. He is proud to have won a number of awards for his teaching and educational activities, including the IEEE Taylor Booth Education Medal and a Lilly Teaching Fellowship. He is one of the leaders of the Commonwealth Information Technology Initiative (CITI). He is a Fellow of the IEEE and the ACM. With Keith Ross, he is the co-author of the textbook, "Computer Networking, a top down approach featuring the Internet (2nd edition)," published by Addison-Wesley Longman.