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Measurement in the Internet

Measurement in the Internet. Paul Barford. University of Wisconsin - Madison. Spring, 2001. Why measure the Internet?. The size, growth, complexity and diversity of the Internet make it impossible to understand, manage, protect or provision without measurement.

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Measurement in the Internet

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  1. Measurement in the Internet Paul Barford University of Wisconsin - Madison Spring, 2001

  2. Why measure the Internet? • The size, growth, complexity and diversity of the Internet make it impossible to understand, manage, protect or provision without measurement. • Prior measurement studies have taught us a great deal • Self-similarity of packet traffic • Ubiquity of power laws • Businesses use measurements to provision, manage and operate • Future developments will require more and/or different measurements

  3. What can be measured in the Internet? • Structure • Topology, routing, CDN’s, wireless, etc. • Traffic • Transport, end-to-end performance, etc. • Users and Applications • WWW, (x,my)Napster, Peer-to-Peer,Streaming, security, etc. • Failures • In all areas • Nefarious behavior • Pattern attacks, port scans

  4. Where are measurements made in the Internet? • For some measurements, this is obvious • Web logs • The goal for other measurements is to be “representative” • Various “Internet weather reports” • Placement of measurement nodes is not a well understood problem • More is better??

  5. How are Internet measurements made? • Passive methods • Application monitors (logs), packet monitors • Active methods • Probes, application simulation • Surveys • Significant infrastructure is always required • All methods present difficulties

  6. When must Internet measurements be made? • Diurnal traffic cycle • Time scales depend on “what” and “how” • Passive measurements are typically continuous • Can generate huge data sets • Many people will not allow access to their logs • Active measurements are typically discrete • Important characteristics can be missed • Probes can be filtered and/or detected

  7. Who is doing Internet Measurements? • Businesses do a great deal of measurement • What measurements are they taking and what do they do with their data? • Instrumentation for measurement-based research is relatively new • Developments over the past 12 years have been slow • 10’s of current studies (see CAIDA and SLAC pages for lists of these) • Most studies are not coordinated and relatively narrowly focused

  8. In the past… • Bellcore Ethernet packet traces – Leland et al. • High time resolution LAN data collected over 4 year period beginning in 1989 • Thorough analysis showed self-similar properties • NPD study – Paxson • Characterized routing and packet behavior in wide area • First installation of large measurement infrastructure

  9. Internet topology: Skitter Project • CAIDA • Internet topology measurement infrastructures • Traceroute studies focused on router/link discovery • Skitter: 17 sources, 54,000 destinations world wide • Data from Skitter is publically available • www.caida.org

  10. Skitter example – BGP paths

  11. Surveyor • Advanced Network Systems • Infrastructure for measuring one-way Internet latency, loss and routes between hosts • 61 sites world wide • GPS enabled • Closed platform (until recently) • www.advanced.org

  12. Surveyor example - delay

  13. Wide Area Web Measurements (WAWM) • Barford and Crovella (Wisconsin & Boston Univ.) • Application level measurement infrastructure • 11 clients (national and international) • GPS enabled • Combined passive and active measurements • Application of critical path analysis to TCP transactions • www.cs.wisc.edu/~pb

  14. Example of WAWM results File transfer delay for 500KB file between Denver and Boston

  15. National Internet Measurement Infrastructure (NIMI) • Paxson (ACIRI), Adams and Mathis (PSC) • Secure management platform for wide area measurements • Designed for general probe installation • Distributed client infrastructure • Principally academic sites (currently 41 world wide) • A number of projects are running on NIMI • www.ncne.nlanr.net

  16. Short Term Challenges of Internet Measurement • Developing methods for gathering more precise data • Current tools are frequently quite poor • Developing methods for analyzing measurement data more thoroughly • What we know about how things work is limited • Developing methods for understanding causes and effects across multiple domains

  17. The future – Global Internet Measurement (GIM) • Ubiquitous measurement capability • Embedded into the design of the Internet • Emphasis on extensible API’s for measurement • Analysis capability must be built in • Measurement quality and soundness • Data formats that enable aggregation that reflects higher level behaviors • Many difficulties • Management, security, privacy, heterogeneity, deployment, etc. • See Performance Evaluation vol. 864 www.elsevier.com/locate/peva

  18. Conclusion • Measurements are necessary for understanding Internet structure and behavior • Rule #1: Expect surprises! • Internet measurements are difficult • Rule #2: Expect the data to be “dirty” • Measurements are necessary for populating and validating any reasonable Internet models • Rule #3: Garbage-in-garbage out • Current measurement infrastructures can provide a great deal of data but fall short of the GIM goal

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