Paper review: End-to-End Packet Delay and Loss Behavior in the Internet

Reviewer: Mike Liu

  1. State the problem the paper is trying to solve.
  2. The main problem the paper is trying to solve is: "How to measure and analyze the end-to-end packet delay and loss behavior in the Internet? "
  3. State the main contribution of the paper: solving a new problem, proposing a new algorithm, or presenting a new evaluation (analysis). If a new problem, why was the problem important? Is the problem still important today? Will the problem be important tomorrow?  If a new algorithm or new evaluation (analysis), what are the improvements over previous algorithms or evaluations? How do they come up with the new algorithm or evaluation? 
  4. The main contribution of the paper is that it presented the idea of measuring round trip delays of small UDP probe packets sent at regular time intervals to analyze the Internet's end-to-end packet delay and loss behavior. They observed such interest phenomena as compression of the probe packets, rapid fluctuations of queing delays over small intervals, etc. They showed in the paper that the UDP echo is not only useful for studying network problems but that it can also be useful in analyzing end-to-end characteristics over different time scales, of connections over the internets. This is a useful problem because it gets at the beginning of analysis of the behavior of load on the Internet. The UDP probe packets are somewhat like ping and may have led to the development of ping in the current day. In understanding packet delay and loss behavior, one can apply this knowledge in the proper design of network algorithms such as routing and flow control algorithms, in dimensioning of buffers and link capacity, and in choosing parameters in simulations and analytics studies. This understanding is also essential for designing the emerging audio and video applications for the Internet. For this last reason also, the problem still is rather relevant today.
  5. Summarize the (at most) 3 key main ideas (each in 1 sentence.) 
  6. The first main idea in the analysis of the data presented in the paper is that the transatlantic link between France and the United States with a bandwidth equal to 128 kb/s is the bottleneck link on the path from INRIA to UMd. The second main idea presented in the analysis was that clp, conditional loss probability, is greater than ulp, unconditional loss probability, for all values of sigma(in ms), the interval between the send times of two successive packets. Third main idea that was presented in the analysis is that the loss gap stays close to 1 even for small values of sigma, which has important consequences for the design of audio and video applications.
  7. Critique the main contribution
  8. What lessons should researchers and builders take away from this work. What (if any) questions does this work leave open?
  9. Researchers should take away lessons on how to construct an analysis of packet delay and loss behavior using the UDP echo tool probe packets. The work leaves open questions of what this analysis would look like today as well as what the implications of the discovery that probe packets are lost randomly except when Internet traffic intensity is very high are.