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Web Replication and Caching Update

Web Replication and Caching Update. Ingrid Melve, UNINETT http://www.desire.org/ DESIRE II project. Context. IETF Web Replication and Caching WREC WG http://www.wrec.org/ draft-melve-taxonomy-00.txt DESIRE II Web searching Web caching. Web replication and caching.

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Web Replication and Caching Update

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  1. Web Replication and Caching Update Ingrid Melve, UNINETT http://www.desire.org/ DESIRE II project

  2. Context • IETF Web Replication and Caching WREC WG • http://www.wrec.org/ • draft-melve-taxonomy-00.txt • DESIRE II • Web searching • Web caching

  3. Web replication and caching • State of web replication and caching • Deployed technology, protocols • Standard concepts and terminology • Replication • Objects • Services and applications • Caching proxies • Objects • System overview • Inter-cache, inter-replica • Client-replica, client-proxy • Network element to caching proxy

  4. Terminology • Cache: transient copies • Sparse working set cache • Replica: persistent copies • Complete idem-potent set replication • Proxy: intermediary program that acts as both a server and a client

  5. Distributed relationships

  6. Distributed relationships • Inter-replica • Cooperation and communication between replica origin servers • Client to replica • Cooperation and communication between clients (user agents & proxies) and replica origin server • Client to proxy • Configuration, cooperation and communication between user agents and a caching proxy • Inter-cache • Cooperation and communication between caching proxies • Network element to proxy cache • Cooperating and communication between cachingproxy and network elements.

  7. Inter-Replica • Replica origin servers • Object replication: SOP • demand driven • batch driven • Replication of services • CGI-scripts with consistent performance • Interoperability of server software • Supplied by information owner

  8. Client to Replica • Optimal replica proximity • Finding an object • Finding the closest copy • Finding the right copy • Examples • URL redirection • DNS redirection • URN resolution • FTP mirror tracker

  9. Client to Proxy • Finding the Proxy • Manual configuration • PAC, Proxy Auto-Configuration script • WPAD, Web Proxy Auto-Discovery • CARP, Cache Array Routing Protocol • Caching proxy directives • HTTP/1.1 Cache-control

  10. Inter-proxy communication • Query for objects • ICP, Internet Cache Protocol • HTCP, HyperText Cache Protocol • Inform about object location in cache mesh • CacheDigest • Load balance • CARP • HTTP/1.1 have extended support for caching proxies

  11. Network element to proxy array • Redirection • SOCKS: firewall (application) • WCCP, Web Cache Coordination Protocol: router (network/transport) • Proprietory protocols: switch (network/link) • Transparent redirection: hijacking web traffic • Added functionality • Load balancing • Redundancy • Fallback

  12. Summing up • Replication and caching • Competing technologies • Complementary technlogies • Ongoing work, rapid development • Replication is in its infancy • Proxy caching is in puberty • Proxy caching commercial products available • Traffic flow is altered at the application layer • Middleware development to be followed

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