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

2. 2 A popular web site Browsers Web Server

3. 3 Congestion slows delivery Browsers Web Servers Routers Networks

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

5. 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. 6 Benefits for Web Publishers Improves quality of service Scales easily as demand grows Offers full-service management Reduces costs

7. 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. 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. 9 Content Distributors 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 Origin Server Content Distributor Content Migrator

10. 10 Rendezvous: Migrator Strategy –operator specifies which resources should “migrate” –migrator makes selection as 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 Content Migrator Origin Server Rule Base HTML Rewriter HTTP Request HTTP Reply

11. 11 Rendezvous: DNS Strategy –URLs in HTML are modified before serving to use “supernames” –browser uses DNS to resolve the supername to a content distributor –Sandpiper custom DNS servers resolve the name to the best distributor Results –high scalability for very busy web servers Origin Server HTML Rewriter Browser Footprint DNS server Content Distributor

12. 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. 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 Distributor load Best Distributor Selection Network status Specific Content Distributor

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

15. 15 Serving HTML from 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. 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. 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. 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 Origin Server Content Distributor Browser

19. 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. 20 Footprint Streaming Architecture Browser Content Migrator Real G2 Server Content Distributor Origin Server Inktomi TS/MCO Real Proxy Footprint Request Processor rendezvous cache fills & live streams Browser

21. 21 Footprint offers publisher-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. 22 Coupling Footprint with ISP caches Used by caching ISPs –for example, AOL Gives Footprint customers –access to logs –control of freshness Browser ISP Caches Content Distributor Origin Server ISP Network

23. 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. 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