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Content Delivery Networks

Content Delivery Networks. iBAND2 May 24, 1999 Dave Farber CTO Sandpiper Networks, Inc. www.sandpiper.net dave@sandpiper.net. A popular web site. Browsers. Web Server. Congestion slows delivery. Networks. Browsers. Routers. Web Servers.

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Content Delivery Networks

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  1. Content Delivery Networks iBAND2 May 24, 1999 Dave Farber CTO Sandpiper Networks, Inc. www.sandpiper.net dave@sandpiper.net

  2. A popular web site Browsers Web Server

  3. Congestion slows delivery Networks Browsers Routers Web Servers

  4. Replicating content closer to users • Reduces load on server • Avoids network congestion Browsers Replicatedcontent Router Web Server

  5. Content Delivery Networks Outsourcing for web publishers lets existing web sites scale serves content closer to end users uses a massive, shared infrastructure provides reserved resources serves all clients

  6. Benefits for Web Publishers • Improves quality of service • Scales easily as demand grows • Offers full-service management • Reduces costs

  7. The Footprint Network • Content Distributors • replicate content • manage shared resources • Content Migrators • determine when to migrate requests • select the best distributor • rewrite HTML • provide publisher control

  8. The Footprint Network • Improves connection to user • bandwidth is monitored for quality • distributors are located near clients • measurements identify the best distributor • Allows capacity to scale • bandwidth can be increased quickly • new distributors can be added easily • Works for ISPs • distributors reduce ISP peering costs • distributors cooperate with ISP caches

  9. Content Distributors ContentDistributor • Strategy • cache HTTP and FTP resources • adjust cache-control directives • publish updates by explicit broadcasting of invalidations,and expiration policy • collect and merges logs • Results • very high hit rates • avoids control problems created by traditional caches Content Migrator Origin Server

  10. Rendezvous: Migrator HTTP Reply HTTP Request • Strategy • operator specifies which resources should “migrate” • migrator makes selectionas resources are served • URLs in HTML are rewritten • Results • easy to deploy • most resources migrate to distributor network • rewriting HTML reduces visits to origin server and allows FTP redirection RuleBase HTMLRewriter ContentMigrator OriginServer

  11. Rendezvous: DNS • Strategy • URLs in HTML are modified before serving to use “supernames” • browser uses DNS to resolve the supernameto a content distributor • Sandpiper custom DNS servers resolve the nameto the best distributor • Results • high scalability for verybusy web servers ContentDistributor Browser FootprintDNS server OriginServer HTMLRewriter

  12. Adapts to traffic conditions Supports a wide variety of content static files - images, downloads, HTML authenticated content dynamic (custom) content audio/video streaming Provides publisher controls access to logs complete control of content freshness coupled with client-side caches Unique Footprint Services

  13. Selecting Best Distributor • Strategy • group client IP addresses • measure network congestion regularly • measure load frequently • use load and congestion data to select best distributor • Results • reduces delays when net is congested • wide area load balancing • high availability of servers Client IP address Network map Best Distributor Selection Network status Distributor load Specific ContentDistributor

  14. Footprint Performance Origin Server With Footprint Commercial Web Server Site Average response time (seconds)

  15. Serving HTMLfrom content distributors • Many sites serve 50% or more HTML • Benefits • increases scalability • improves performance • Challenges • bookmarks on resources • cookies and authenticated content • customized dynamic content

  16. Custom domain names • Distributor aliases for web publishers • http://38.200.111.132 /www.hotstuff.com/products • http://www41.hotstuff.com /products • Benefits • name recognition value in each URL • bookmarks remain under publisher’s control • browsers send cookies and passwords to distributors • Java sandbox can talk to content distributors

  17. Cookies and Authentication • Cookie support • custom domain names make cookies available • cookies are logged on receipt • cookies are forwarded when custom content is required • Authentication support • custom domain names make passwords available • requests are forwarded for authorization • content is cached & served by content distributor

  18. Custom content • Dynamic content is customized per user • Many custom pages built from common elements • ad insertions • custom home pages • product status updates • Distributor-Side Include • origin server provides minimal custom content • Content Distributor assembles elements OriginServer ContentDistributor Browser

  19. Streaming in Footprint Scales to vast numbers of viewers without requiring changes to server Rendezvous clients with best server using Sandpiper’s proprietary technology Replicates streams on demand live via Real proxy (splitter) on-demand via Inktomi’s Media Cache Option Uses existing shared infrastructure

  20. Footprint StreamingArchitecture Origin Server Browser Real G2Server Content Migrator rendezvous Content Distributor FootprintRequest Processor cache fills & live streams Browser RealProxy Inktomi TS/MCO

  21. Footprint offerspublisher-friendly caching • Content distributors: • provide activity logs • keep resources “fresh” • guarantee local bandwidth • guarantee local disk space • handle more than HTTP traffic • give publishers control

  22. Coupling Footprintwith ISP caches ISP Caches • Used by caching ISPs • for example, AOL • Gives Footprint customers • access to logs • control of freshness ContentDistributor Browser ISP Network OriginServer

  23. Working for ISPs • For Demand-side ISPs, Footprint • reduces bandwidth costs • improves end user performance • couples with traditional caches • provides publisher-friendly caching • can serve browsers located anywhere • For Supply-side ISPs, Footprint • extends ISP hosting services • offers differentiated services • increases the “reach” of your web publishers • provides additional source of revenue

  24. Conclusion Scaling Internet servers requires serving content closer to users Content Delivery Networks give publishers a way to scale Sandpiper’s Footprint provides a comprehensive set of benefits today Content Delivery Networks will become a natural part of the Internet infrastructure

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