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10th June 2004
Computer Laboratory > Research > Systems Research Group > NetOS > Seminars > 10th June 2004

Measurement-in-the-middle: Inferring end-end path properties through passive measurements

Gianluca Iannaccone
In this talk, we consider the problem of inferring end-end path properties and the behavior of TCP senders observing packets crossing an IP backbone. We describe a 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 from measurements taken at a single point in the middle of the end-end path.
We propose a classification methodology for out-of-sequence packets and a set of methods to infer and keep track of the sender's congestion window and the connection round trip time. Given the location of the measurement points within a large Internet Service Provider, we are able to analyze more than 10 million connections, with senders located in more than 45% of the autonomous systems in today's Internet. Our measurements show a relatively consistent amount of out-of-sequence packets of less than 5%. We find that few packets experience pathological problems such as in-network duplication or in-network reordering. Moreover, the TCP sender throughput is frequently limited by a lack of data to send, and the congestion control flavor often has minimal impact on throughput.
This is joint work with Sharad Jaiswal, Jim Kurose and Don Towsley (Univ. Massachusetts) and Christophe Diot (Intel).