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On the Use and Performance of Content Distribution Networks

On the Use and Performance of Content Distribution Networks. Balachander Krishnamurthy Craig Wills Yin Zhang. Presenter: Wei Zhang CSE Department of Lehigh University. What are Content Distribution Networks?.

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On the Use and Performance of Content Distribution Networks

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  1. On the Use and Performance of Content Distribution Networks Balachander Krishnamurthy Craig Wills Yin Zhang Presenter: Wei Zhang CSE Department of Lehigh University

  2. What are Content Distribution Networks? • Content distribution networks (CDNs) are a mechanism to deliver content to end users on behalf of origin Web sites. • Content distribution offloads work from origin servers by serving some or all of the contents of Web pages.

  3. Referenced CDNs and their URLs

  4. CDN Techniques • DNS redirection • Full-site content delivery • The origin server modifies its DNS zone file; • The CDN server either serves the content from its cache or forwards on the request to origin server. • Partial-site content delivery (primarily for images) • i.e. www.foo.com/bar.gif -> foo.speedera.net/www.foo.com/bar.gif • URL rewriting • An origin server dynamically rewrites URL links in generated pages to redirect clients to different content servers.

  5. Use of Content Distribution Networks • Change Characteristics of CDN-Served Content • CDNs are serving little dynamically generated content that is actually changing on each access.

  6. Use of Content Distribution Networks • Nature of HTTP-Request CDN content • Images account for 96~98% of the CDN-served objects, but only 40~60% of the CDN-served bytes. • Among the CDNs, Akamai servers over 85~98% of the CDN-served objects in the proxy logs and a comparable range of the CDN-served bytes.

  7. Performance of CDNs • Response Time Results

  8. Performance of CDNs • Performance for individual clients

  9. Performance of CDNs • DNS load balancing

  10. Performance of CDNs • DNS load balancing

  11. Conclusion • Most CDNs provide better download performance for the U.S. clients than the U.S. origin sites. • CDNs should increase the DNS TTL given to a client unless the servers are known to be loaded.

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