World Wide Web Caching Trends and Techniques by Ersan Bilik 11 May 2005
Why ? <ul><li>Bandwith Savings </li></ul><ul><li>Server Load Balancing </li></ul><ul><li>Network Latency Reduction </li></...
Proxy Caching <ul><li>Intercepts HTTP request. </li></ul><ul><li>Requested object found ? Then return it </li></ul><ul><li...
Disadvantages of Proxy Caching <ul><li>When the cache server is unavailable, then served clients won’t reach content. </li...
So, What to do ? <ul><li>Locating nearby proxies </li></ul><ul><li>Browser Auto-Configuration </li></ul><ul><li>Proposed b...
Reverse Proxy Cache <ul><li>Cache it near the origin of contents instead of near the clients. </li></ul><ul><li>Good for s...
Transparent Proxy Caching <ul><li>Intercepts HTTP request </li></ul><ul><li>Redirecting them to web cache servers </li></u...
Advantages & Disadvantages <ul><li>No need to configure web browsers manually ! </li></ul><ul><li>Additional network traff...
Adaptive Web Caching <ul><li>Aim: Dynamically Bring proxy servers closer to “hot spots” </li></ul><ul><li>What is hot spot...
How CGMP algorithm works ? <ul><li>Nodes “Learn” the enviroment </li></ul><ul><li>Sounds like Artifical Intelligence (Gene...
Push Caching <ul><li>Aim : Keep requested data close to clients </li></ul><ul><li>Not like adaptive caching </li></ul><ul>...
Active Caching  <ul><li>Problem : 30% of information requested by clients are dynamic data’s (such as cookies) </li></ul><...
Cache Deployment Options <ul><li>Consumer Oriented </li></ul><ul><ul><li>Proxy Caching, Tranparent Proxy Caching </li></ul...
Hierarchical Caching <ul><li>Aim: Have a series of caches hierarchically arranged in a tree like structure </li></ul><ul><...
Intercache Communication <ul><li>It is desirable to caches query eachother ! </li></ul><ul><li>There are five well known p...
Hash Based Request Routing <ul><li>Aim: Perform load balancing in cache clusters </li></ul><ul><li>Why to use a long strin...
Optimized DISK I/O`s <ul><li>Data Structers to optimize caching </li></ul><ul><li>Hash tables </li></ul><ul><li>Reduce I/O...
Micro Kernel Architectures <ul><li>Resource Allocation </li></ul><ul><li>Task Execution </li></ul><ul><li>Disk Access </li...
Content Prefetching <ul><li>Retriving data from remote servers in anticipation client requests </li></ul><ul><li>What to p...
Cache Consistency <ul><li>What will happen to out-to-date objects ? </li></ul><ul><li>Instead of checking when a request c...
Conclusion & Questions & Comments <ul><li>Web Caching is important technology </li></ul><ul><li>Bandwith Savings </li></ul...
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World Wide Web Caching

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World Wide Web caching trends and techniques

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World Wide Web Caching

  1. 1. World Wide Web Caching Trends and Techniques by Ersan Bilik 11 May 2005
  2. 2. Why ? <ul><li>Bandwith Savings </li></ul><ul><li>Server Load Balancing </li></ul><ul><li>Network Latency Reduction </li></ul><ul><li>Content Availabilitiy </li></ul><ul><li>Why we needed caching ? </li></ul><ul><li>Growth of Internet ! </li></ul><ul><li>At 90`s FTP usage was %44 , nowadays HTTP usage is between 75% and 80% </li></ul>
  3. 3. Proxy Caching <ul><li>Intercepts HTTP request. </li></ul><ul><li>Requested object found ? Then return it </li></ul><ul><li>Else , go to object’s home server and cache it. </li></ul><ul><li>Return cached object </li></ul>
  4. 4. Disadvantages of Proxy Caching <ul><li>When the cache server is unavailable, then served clients won’t reach content. </li></ul><ul><li>Web browsers should be manually configured to appropriate proxy cache </li></ul><ul><li>In any change of proxy server all browsers should be manually configured again ! </li></ul>
  5. 5. So, What to do ? <ul><li>Locating nearby proxies </li></ul><ul><li>Browser Auto-Configuration </li></ul><ul><li>Proposed by Internet Engineering Task Force (IETF) </li></ul><ul><li>Web Proxy Auto Discovery Protocol (WPAD) </li></ul><ul><li>Relies on DNS records and DHCP to locate an automatic proxy configuration file (APC) </li></ul>
  6. 6. Reverse Proxy Cache <ul><li>Cache it near the origin of contents instead of near the clients. </li></ul><ul><li>Good for servers with a huge number of requests </li></ul><ul><li>For e.g. Hosting farms </li></ul><ul><li>Can’t be an alternative of Client-Side Proxy Caching </li></ul>
  7. 7. Transparent Proxy Caching <ul><li>Intercepts HTTP request </li></ul><ul><li>Redirecting them to web cache servers </li></ul><ul><li>After that, it works like a proxy caching </li></ul><ul><li>Works like a router </li></ul>
  8. 8. Advantages & Disadvantages <ul><li>No need to configure web browsers manually ! </li></ul><ul><li>Additional network traffic ! </li></ul><ul><li>No Acknowledge ! </li></ul><ul><li>Can be used with a L4 switcher ! </li></ul>
  9. 9. Adaptive Web Caching <ul><li>Aim: Dynamically Bring proxy servers closer to “hot spots” </li></ul><ul><li>What is hot spot ? </li></ul><ul><li>A highly requested information </li></ul><ul><li>Cache Group Management Control (CGMP) </li></ul><ul><li>Content Routing Protocol (CRP) </li></ul>
  10. 10. How CGMP algorithm works ? <ul><li>Nodes “Learn” the enviroment </li></ul><ul><li>Sounds like Artifical Intelligence (Genetic algorithms) </li></ul><ul><li>Nodes votes the other nodes </li></ul><ul><li>The higher fitness values of nodes, the more nodes will join to that mesh (sub network) </li></ul>
  11. 11. Push Caching <ul><li>Aim : Keep requested data close to clients </li></ul><ul><li>Not like adaptive caching </li></ul><ul><li>Adaptive caching targets on : The boundries can englarge </li></ul><ul><li>Push caching targets on : Contenting datas </li></ul>
  12. 12. Active Caching <ul><li>Problem : 30% of information requested by clients are dynamic data’s (such as cookies) </li></ul><ul><li>In future, it will be more ! </li></ul><ul><li>Use applets for dynamic content ! </li></ul><ul><li>Cache the dynamic content </li></ul><ul><li>Use dynamic content locally </li></ul><ul><li>(at cache) </li></ul>
  13. 13. Cache Deployment Options <ul><li>Consumer Oriented </li></ul><ul><ul><li>Proxy Caching, Tranparent Proxy Caching </li></ul></ul><ul><li>Provider Oriented </li></ul><ul><ul><li>Reverse Proxy Caching </li></ul></ul><ul><li>Strategic Points in Network </li></ul><ul><ul><li>Adaptive Caching </li></ul></ul><ul><li>Advantages & Disadvantages ? </li></ul>
  14. 14. Hierarchical Caching <ul><li>Aim: Have a series of caches hierarchically arranged in a tree like structure </li></ul><ul><li>When request arrived , leverage from eachother. </li></ul><ul><li>Child Caches query parent caches and children query eachother. </li></ul>
  15. 15. Intercache Communication <ul><li>It is desirable to caches query eachother ! </li></ul><ul><li>There are five well known protocols which deals with this issue. </li></ul><ul><li>ICP,cache digest,CRP,CARP,WCCP </li></ul><ul><li>ICP is the oldest and most mature </li></ul><ul><li>ICP queries other caches to determine the best way to respond requested object. </li></ul><ul><li>There is a relation between depth of tree and latency </li></ul>
  16. 16. Hash Based Request Routing <ul><li>Aim: Perform load balancing in cache clusters </li></ul><ul><li>Why to use a long string when u can use 128 bits to define everything ? </li></ul><ul><li>Microsoft CARP doesn’t query cache’s but request url by a hashing function </li></ul>
  17. 17. Optimized DISK I/O`s <ul><li>Data Structers to optimize caching </li></ul><ul><li>Hash tables </li></ul><ul><li>Reduce I/O costs will effect performance </li></ul>
  18. 18. Micro Kernel Architectures <ul><li>Resource Allocation </li></ul><ul><li>Task Execution </li></ul><ul><li>Disk Access </li></ul><ul><li>Transfer Times </li></ul><ul><li>Windows NT and UNIX is not a suitable operation system for web caching </li></ul>
  19. 19. Content Prefetching <ul><li>Retriving data from remote servers in anticipation client requests </li></ul><ul><li>What to prefetch next ? </li></ul><ul><li>A smart algorithm can reduce latency up to 50% </li></ul>
  20. 20. Cache Consistency <ul><li>What will happen to out-to-date objects ? </li></ul><ul><li>Instead of checking when a request comes, check it periodically.. </li></ul><ul><li>But whom to check ? Server to proxy or proxy to server ? </li></ul><ul><li>Time to Live (TTL) </li></ul>
  21. 21. Conclusion & Questions & Comments <ul><li>Web Caching is important technology </li></ul><ul><li>Bandwith Savings </li></ul><ul><li>Network Latency Reduction </li></ul>
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