2. (C) Copyright PodsCat, 1998 A Smart Internet Caching System1 E-mail : chunpo@csie.chu.edu.tw Director : D r. 張燕光 Speaker : Chun-Po Kuo From : http://info.isoc.org/isoc/whatis/conferences/inet/96/proceedings/a4/a4_3.htm

3. (C) Copyright PodsCat, 1998 A Smart Internet Caching System2 Outline  Introduction  Background and previous work  System Model  System design  System Protocols  Dimensioning and performance issues  Conclusions

4. (C) Copyright PodsCat, 1998 A Smart Internet Caching System3 Introduction  long response time due to:  load on the server  load on the communication line  system techniques are:  Caching of recently accessed file  Pre-fetching of files which may be accessed shortly.  Deferment of loading large and/or low priority files.  Automatic updating of frequently used pages during off- peak times.  File compression and difference.

5. (C) Copyright PodsCat, 1998 A Smart Internet Caching System4 Background and previous work  Two techniques used to implement proxies are mirroring, and caching.  Mirror suffers from a number of drawbacks :  Files are mirrored only at periodic intervals.  Many mirrored files will rarely, or never, be accessed.  Users may not be aware of the best mirror site to use.  A mirror can only store a small fraction of the files on the Internet.

6. (C) Copyright PodsCat, 1998 A Smart Internet Caching System5 The System Model

7. (C) Copyright PodsCat, 1998 A Smart Internet Caching System6 Performance-enhancing measuresPerformance-enhancing measures  A number of techniques are used to improve performance.  A conventional cache  File pre-fetching  Deferred file loading  Automatic updating  File compression and differencing  three types of document requests  User requests  Predicted request  Update requests

8. (C) Copyright PodsCat, 1998 A Smart Internet Caching System7 System Model

9. (C) Copyright PodsCat, 1998 A Smart Internet Caching System8 Algorithm for the local gateway  The prime responsibilities of the local gateway are :  Record all user requests, and maintain a history information of previous requests.  Maintain a cache of recently loaded document.  Decide which documents are required for the predicted and update requests.  Transmit predicted and update requests for documents to the remote gateway.  Receive and decompress documents.  Forward documents to user.

10. (C) Copyright PodsCat, 1998 A Smart Internet Caching System9 Local Gateway

11. (C) Copyright PodsCat, 1998 A Smart Internet Caching System10 Algorithms for the remote gateway  The prime responsibilities of the remote gateway are :  Receive requests from local gateway  Requests and load documents from WWW servers or other caches.  Use heuristics to predict which other documents might soon be requested on the basis of the contents of requests document.  Compress these documents will not have yet been requested, in which case a push or forces send is required.

12. (C) Copyright PodsCat, 1998 A Smart Internet Caching System11 Remote Gateway

13. (C) Copyright PodsCat, 1998 A Smart Internet Caching System12 Conclusion  Detailed analysis and experimentation is required.  Having demonstrated their feasibility, a product could be developed for wider implementation.