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Web Caching and CDNs

This document discusses the critical role of web caching and Content Delivery Networks (CDNs) in improving web performance. It outlines the motivations for using these technologies, including reducing response times and alleviating server overload. The document also examines the structure of CDNs, their operational models compared to traditional caching, and highlights the benefits and drawbacks, such as latency issues and costs of implementing proxy servers. The interplay between caching, CDNs, and peer-to-peer (P2P) systems is also explored, showcasing their significance in modern content distribution.

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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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