1. Web caching solving somebody else’s problem Ingrid Melve Networld + Interop 97 / Web caching

2. DESIRE Development of a European Service for Information on Research and Education • EU funded project with 22 partners, 3 work on web caching • Deliver new services by employment of today’s available technology • Web caching is one of 8 work packages • Web cache work is lead by UNINETT with SURFnet, Utrecht University and TERENA as participants Networld + Interop 97 / Web caching

3. Web caching - solving somebody else’s problem • Introduction to web proxy caching • Web cache systems • Benefits • Policy and security • Conclusion Networld + Interop 97 / Web caching

4. Introduction to web proxy caching • What are the web problems? • Content • Too slow • Kills the network • Web solution: local copies of objects • Speed up retrieval • Reduce traffic • # connections • bytes over wire Networld + Interop 97 / Web caching

5. Web cache systems • Stand alone proxy cache • Chain of proxy caches • Mesh of proxy caches • cooperating system • Intranet • Internet Service Provider (ISP) • Inter-ISP Networld + Interop 97 / Web caching

6. Stand alone proxy cache • Proxy on firewall • Small company, little traffic Web server Client Cache mesh Networld + Interop 97 / Web caching

7. Chain of proxy caches • Stringing two proxies after each other • Firewall + Internet Service Provider • Intranet: local office connected through central office • A chain is as strong as the weakest link Networld + Interop 97 / Web caching

8. Mesh of proxy caches • Cooperating system • redundancy • scaling (Internet traffic doubles every year) • fall back gracefully • Inter-cache communication • Internet Cache Protocol (ICP) • Proprietary systems (Cisco’s Cache Director) • Trade off • Adds local traffic • Reduces expensive external traffic Networld + Interop 97 / Web caching

9. Benefits of web caching • Savings on bandwidth • Small first level cache: 3 Gbyte/month • estimate best case (256 Kbps line) 4.5 Gbyte/month • Large first level cache: 7 Gbyte/month • estimate best case 35 Gbyte/month • Top level cache (12S + 3L): 30 Gbyte/month • estimate best case 90 Gbyte/month • Latency reduction • most documents are located in the US • download time is reduced • 1.2 hours/month per employee at Utrecht University • Eliminate bottlenecks by caching Networld + Interop 97 / Web caching

10. Trends in web technology • Dynamic documents • changing • delivered on the fly (cgi-scripts, databases) • recognizable parts • Push technology • may be cache friendly • caching is primitive push, moves objects closer to users • Statistics and usage patterns • web server admins want reliable statistics • Access control Networld + Interop 97 / Web caching

11. Policy and security • Firewalls should have caching proxies • Intranets benefit from cache systems • Filtering content (PICS, babysitters) • Routing and traffic flow • Proxy log information may be sensitive • Access control mechanisms Networld + Interop 97 / Web caching

12. Costs and benefits • Cost • hardware • software • management, configuration • Benefit • reduced latency • significant, around 3 sec per object for .com • reduced traffic (byte hit rate) • first level 35-50 % • second level 15-35 % Networld + Interop 97 / Web caching

13. Web caching is good • saves time • saves money • provides better service to users • reduces overall traffic on the Internet Networld + Interop 97 / Web caching