WebWave: Globally Load Balanced Fully Distributed Caching of Hot Published Documents

Document publication service over such a large network as the Internet challenges us to harness available server and network resources to meet fast growing demand. In this paper, we show that large-scale dynamic caching can be employed to globally minimize server idle time, and hence maximize the aggregate server throughput of the whole service. To be efficient, scalable and robust, a successful caching mechanism must have three properties: (1) maximize the global throughput of the system, (2) find cache copies without recourse to a directory service, or to a discovery protocol, and (3) be completely distributed in the sense of operating only on the basis of local information. In this paper, we develop a precise definition, which we call tree load-balance (TLB), of what it means for a mechanism to satisfy these three goals. We present an algorithm that computes TLB off-line, and a distributed protocol that induces a load distribution that converges quickly to a TLB one. Both algorithms place cache copies of immutable documents, on the routing tree that connects the cached document's home server to its clients, thus enabling requests to stumble on cache copies en route to the home server.Harvard University; The Saudi Cultural Mission to the U.S.A

Diffusion-based Caching along Routing Paths

Caching for the Web can be beneficial in different ways: not only can it reduce network traffic and client response time, but it can also enable large scale server load balancing. In this paper, we present preliminary simulation data to characterize the performance of WebWave, a diffusion-based caching protocol for server load balancing that we have recently proposed. Initial results suggest that WebWave indeed achieves load balance, even under self-similar request load. Furthermore, the number of cache copies created by WebWave appears to be within acceptable levels. 1 Introduction Much current Internet research and development centers around caching as a means to eliminate the redundant retransmission of information over expensive communication lines. In contrast, we advocate the use of caching also for the purpose of deploying and harnessing additional computation and storage, in the network fabric itself. Our original concept---called WebWave [12]---and subsequent theoretical de..

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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 documentcaching at the application level in document transfer services. Wehave collected traces of actual executions of Mosaic, reflecting over half a million user requests for WWW documents. Using those traces, we study the tradeoffs 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 muchlower hit rate is possible in terms of bytes, because most profitably-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 bycaching at the session level (which is straightforward to implement) is nearly all of that achievable at the LAN level (where caching is more difficult to implement). However, when resource requirements are considered, LAN level caching becomes much more desirable, since it can achieveagiven level of caching performance using a much smaller amountofcache space. Finally,we 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 differences in the potential for sharing these two documenttypes among multiple users