With the increasing demand for document transfer services such as the World Wide Web comes a need for better resource management to reduce the latency of documents in these systems. To address this need, we analyze the potential for document c a c hing at the application level in document transfer services. We h a ve collected traces of actual executions of Mosaic, re ecting over half a million user requests for WWW documents. Using those traces, we study the tradeo s between caching at three levels in the system, and the potential for use of application-level information in the caching system. Our traces show that while a high hit rate in terms of URLs is achievable, a much l o wer hit rate is possible in terms of bytes, because most pro tably-cached documents are small. We consider the performance of caching when applied at the level of individual user sessions, at the level of individual hosts, and at the level of a collection of hosts on a single LAN. We show that the performance gain achievable by c a c hing at the session level (which is straightforward to implement) is nearly all of that achievable at the LAN level (where caching is more di cult to implement). However, when resource requirements are considered, LAN level caching becomes much more desirable, since it can achieve a g i v en level of caching performance using a much smaller amount o f c a c he space. Finally, w e consider the use of organizational boundary information as an example of the potential for use of application-level information in caching. Our results suggest that distinguishing between documents produced locally and those produced remotely can provide useful leverage in designing caching policies, because of di erences in the potential for sharing these two document t ypes among multiple users.

No abstract

World-Wide Web (WWW) services have grown to levels where signi cant delays are expected to happen. Techniques like pre-fetching are likely to help users to personalize their needs, reducing their waiting times. However, prefetching is only e ective if the right documents are identi ed and if user's move is correctly predicted. Otherwise, pre-fetching will only waste bandwidth. Therefore, it is productive to determine whether a revisit will occur or not, before starting pre-fetching.In this paper we develop two user models that help determining user's next move. One model uses Random Walk approximation and the other is based on Digital Signal Processing techniques. We also give hints on how to use such models with a simple pre-fetching technique that we are developing.

No abstract