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Web Caching and CDNs

Web Caching and CDNs. March 3, 2004. Content Distribution. Motivation Network path from server to client is slow/congested Web server is overloaded Web Caching Store content in cache near client CDNs Actively replicate content at servers in network Peer-to-Peer File Sharing. Scenario.

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Web Caching and CDNs

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  1. Web Caching and CDNs March 3, 2004

  2. Content Distribution • Motivation • Network path from server to client is slow/congested • Web server is overloaded • Web Caching • Store content in cache near client • CDNs • Actively replicate content at servers in network • Peer-to-Peer File Sharing

  3. Scenario Content Provider origin server

  4. Scenario Content Provider origin server proxy server

  5. Benefits • Reduce response time for client request • Reduce traffic on an institution’s access link. • Internet dense with caches enables “poor” content providers to effectively deliver content

  6. Drawbacks?

  7. Drawbacks? • Latency • Cooperative caching = even greater latency • Cost of deploying proxy server • Stale data

  8. Content distribution networks (CDNs) origin server in North America CDN distribution node CDN server in S. America CDN server in Asia CDN server in Europe

  9. CDNs • Request base object from origin server • Objects to be fetched from CDN have URLhttp://www.cdn.com/www.foo.com/sports/ruth.gif • DNS lookup for www.cdn.com • DNS server maps to closest server • Request objects from www.cdn.com

  10. CDNs vs. Caching?

  11. CDNs vs. Caching? • Different business models • CDNs = no infrastructure required for client • CDNs use push model to keep data fresh • CDNs don’t incur latency of cache miss

  12. P2P • Relationship of CDNs, caching, and P2P model?

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