Quantile sampling for practical delay monitoring in Internet backbone networks

Baek Young Choi, Sue Moon, Rene Cruz, Zhi Li Zhang, Christophe Diot

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Point-to-point delay is an important network performance measure as it captures service degradations caused by various events. We study how to measure and report delay in a concise and meaningful way for an ISP, and how to monitor it efficiently. We analyze various measurement intervals and potential metric definitions. We find that reporting high quantiles (between 0.95 and 0.99) every 10-30 min as the most effective way to summarize the delay in an ISP. We then propose an active probing scheme to estimate a high quantile with bounded error. We show that only a small number of probes are sufficient to provide an accurate estimate. We validate the proposed delay monitoring technique on real data collected on the Sprint IP backbone network. To make our work complete, we lastly compare the overhead of our active probing technique with a passive sampling scheme and show that for delay measurement, active probing is more practical.

Original languageEnglish (US)
Pages (from-to)2701-2716
Number of pages16
JournalComputer Networks
Issue number10
StatePublished - Jul 11 2007

Bibliographical note

Funding Information:
Zhi-Li Zhang received a B.S. degree in Computer Science from Nanjing University, China, in 1986 and his M.S. and Ph.D. degrees in computer science from the University of Massachusetts in 1992 and 1997. In 1997 he joined the Computer Science and Engineering faculty at the University of Minnesota, where he is currently a professor. From 1987 to 1990, he conducted research in Computer Science Department at Århus University, Denmark, under a fellowship from the Chinese National Committee for Education. He has held visiting positions at Sprint Advanced Technology Labs; IBM T.J. Watson Research Center; Fujitsu Labs of America, Microsoft Research China, and INRIA, Sophia-Antipolis, France.


  • Active probing
  • Delay
  • Performance monitoring


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