Preprint version. Published in The 2nd ACM SIGCOMM Workshop on Internet Measurement Proceedings: Marseille, FR, November 6, 2002, pages 97-105.
Copyright © ACM 2002. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in The 2nd ACM SIGCOMM Workshop on Internet Measurement Proceedings, November 6, 2002, and is available at http://dx.doi.org/10.1145/637201.637216
NOTE: At the time of publication, the author John Bellardo was not yet affiliated with Cal Poly.
The Internet architecture provides an unsequenced datagram delivery service. Nevertheless, many higher-layer protocols, such as TCP, assume that packets are usually delivered in sequence, and consequently suffer significant degradation when packets are reordered in flight. While there have been several recent proposals to create protocols that adapt to reordering, evaluating their effectiveness requires understanding the dynamics of the reordering processes prevalent in the Internet. Unfortunately, Internet packet sequencing is a poorly characterized and understudied behavior. This failing can be largely attributed to the lack of accurate and universally applicable methods for measuring packet reordering. In this paper, we describe a new set of active measurement techniques that can reliably estimate one-way end-to-end reordering rates to and from arbitrary TCP-based servers. We validate these tools in a controlled setting and show how they can be used to measure the time-domain distribution of the reordering process along a given path.