Packet-dispersion techniques and a capacity-estimation methodology

  • Authors:

  • Constantinos Dovrolis;Parameswaran Ramanathan;David Moore

  • Affiliations:

  • College of Computing, Georgia Institute of Technology, Atlanta, GA;University of Wisconsin, Madison, WI;Cooperative Association for Internet Data Analysis (CAIDA), the University of California at San Diego, San Diego Supercomputer Center, La Jolla, CA

  • Venue:
  • IEEE/ACM Transactions on Networking (TON)
  • Year:
  • 2004

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Abstract

The packet-pair technique aims to estimate the capacity of a path (bottleneck bandwidth) from the dispersion of two equal-sized probing packets sent back to back. It has been also argued that the dispersion of longer packet bursts (packet trains) can estimate the available bandwidth of a path. This paper examines such packet-pair and packet-train dispersion techniques in depth. We first demonstrate that, in general, packet-pair bandwidth measurements follow a multimodal distribution and explain the causes of multiple local modes. The path capacity is a local mode, often different than the global mode of this distribution. We illustrate the effects of network load, cross-traffic packet-size variability, and probing packet size on the bandwidth distribution of packet pairs. We then switch to the dispersion of long packet trains. The mean of the packet-train dispersion distribution corresponds to a bandwidth metric that we refer to as average dispersion rate (ADR). We show that the ADR is a lower bound of the capacity and an upper bound of the available bandwidth of a path. Putting all of the pieces together, we present a capacity-estimation methodology that has been implemented in a tool called pathrate. We report on our experiences with pathrate after having measured hundreds of Internet paths over the last three years.