A case for delay-conscious caching of Web documents
01 Sep 1997-Vol. 29, pp 997-1005
TL;DR: This paper presents a new, delay-conscious cache replacement algorithm LNC-R-W3 which maximizes a performance metric called delay-savings-ratio and compares it with other existing cache replacement algorithms, namely LRU and LRU-MIN.
Abstract: Caching at proxy servers plays an important role in reducing the latency of the user response, the network delays and the load on Web servers. The cache performance depends critically on the design of the cache replacement algorithm. Unfortunately, most cache replacement algorithms ignore the Web's scale. In this paper we argue for the design of delay-conscious cache replacement algorithms which explicitly consider the Web's scale by preferentially caching documents which require a long time to fetch to the cache. We present a new, delay-conscious cache replacement algorithm LNC-R-W3 which maximizes a performance metric called delay-savings-ratio. Subsequently, we test the performance of LNC-R-W3 experimentally and compare it with the performance of other existing cache replacement algorithms, namely LRU and LRU-MIN.
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Dissertation•
04 Dec 2003
4 citations
Cites background from "A case for delay-conscious caching ..."
...For example, the Least Normalized Cost Replacement (LNC-R) [96] policy incorporates the access frequency, transfer time and the size, while the Server-assisted policy uses a resource’s fetching cost, size, and next request time [29]....
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01 Jan 1999
TL;DR: In this paper, the authors present an on-line algorithm that captures and maintains an accurate popularity of Web objects requested through a caching proxy, and propose a novel cache replacement policy that uses such information to generalize the well-known GreedyDual-Size algorithm, and show the superiority of their proposed algorithm by comparing it to a host of recently-proposed and widely-used algorithms using extensive trace-driven simulations and a variety of performance metrics.
Abstract: Web caching aims to reduce network traAEc, server load, and user-perceived retrieval delays by replicating \popular" content on proxy caches that are strategically placed within the network. While key to e ective cache utilization, popularity information (e.g. relative access frequencies of objects requested through a proxy) is seldom incorporated directly in cache replacement algorithms. Rather, other properties of the request stream (e.g. temporal locality and content size), which are easier to capture in an on-line fashion, are used to indirectly infer popularity information, and hence drive cache replacement policies. Recent studies suggest that the correlation between these secondary properties and popularity is weakening due in part to the prevalence of eAEcient client and proxy caches (which tend to mask these correlations). This trend points to the need for proxy cache replacement algorithms that directly capture and use popularity information. In this paper, we (1) present an on-line algorithm that e ectively captures and maintains an accurate popularity pro le of Web objects requested through a caching proxy, (2) propose a novel cache replacement policy that uses such information to generalize the well-known GreedyDual-Size algorithm, and (3) show the superiority of our proposed algorithm by comparing it to a host of recently-proposed and widely-used algorithms using extensive trace-driven simulations and a variety of performance metrics.
4 citations
03 Jun 2005
TL;DR: The proposed scheme is efficient in reducing intercluster traffic and improving response time and the experimental results show that most updates are minor and patches are generally smaller than the original file.
Abstract: A peer-distributed Web caching scheme, with incremental update, is proposed that allows a client to retrieve a 'patch' from the original server and the 'patchable' stale cache from a local or a peer cache storage. The stale cache together with the patch then regenerates the up-to-date file for the client. The protocol of the scheme is described and the benefits are analysed. Implementation issues are discussed. The experimental results show that most updates are minor and patches are generally smaller than the original file. The proposed scheme is efficient in reducing intercluster traffic and improving response time.
4 citations
TL;DR: A new delay conscious cache replacement algorithm that considers the retrieval time of the document from servers in addition to the frequency of references to the document, the document size, and an ageing factor and maximizes a performance metric called Communication Delay Ratio (CDR).
4 citations
References
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01 Jun 1993
TL;DR: The LRU-K algorithm surpasses conventional buffering algorithms in discriminating between frequently and infrequently referenced pages, and adapts in real time to changing patterns of access.
Abstract: This paper introduces a new approach to database disk buffering, called the LRU-K method The basic idea of LRU-K is to keep track of the times of the last K references to popular database pages, using this information to statistically estimate the interarrival times of references on a page by page basis Although the LRU-K approach performs optimal statistical inference under relatively standard assumptions, it is fairly simple and incurs little bookkeeping overhead As we demonstrate with simulation experiments, the LRU-K algorithm surpasses conventional buffering algorithms in discriminating between frequently and infrequently referenced pages In fact, LRU-K can approach the behavior of buffering algorithms in which page sets with known access frequencies are manually assigned to different buffer pools of specifically tuned sizes Unlike such customized buffering algorithms however, the LRU-K method is self-tuning, and does not rely on external hints about workload characteristics Furthermore, the LRU-K algorithm adapts in real time to changing patterns of access
1,033 citations
"A case for delay-conscious caching ..." refers methods in this paper
...We call the resulting cache replacement algorithm for proxy caching on the Web LNC-R-W3....
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...Subsequently, we test the performance of LNC-R-W3 experimentally and compare it with the performance of other existing cache replacement algorithms, namely LRU and LRU-MIN....
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22 Jan 1996
TL;DR: The design and performance of a hierarchical proxy-cache designed to make Internet information systems scale better are discussed, and performance measurements indicate that hierarchy does not measurably increase access latency.
Abstract: This paper discusses the design and performance of a hierarchical proxy-cache designed to make Internet information systems scale better. The design was motivated by our earlier trace-driven simulation study of Internet traffic. We challenge the conventional wisdom that the benefits of hierarchical file caching do not merit the costs, and believe the issue merits reconsideration in the Internet environment.
The cache implementation supports a highly concurrent stream of requests. We present performance measurements that show that our cache outperforms other popular Internet cache implementations by an order of magnitude under concurrent load. These measurements indicate that hierarchy does not measurably increase access latency. Our software can also be configured as a Web-server accelerator; we present data that our httpd-accelerator is ten times faster than Netscape's Netsite and NCSA 1.4 servers.
Finally, we relate our experience fitting the cache into the increasingly complex and operational world of Internet information systems, including issues related to security, transparency to cache-unaware clients, and the role of file systems in support of ubiquitous wide-area information systems.
853 citations
"A case for delay-conscious caching ..." refers methods in this paper
...Subsequently, we test the performance of LNC-R-W3 experimentally and compare it with the performance of other existing cache replacement algorithms, namely LRU and LRU-MIN....
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Book•
01 Oct 1973
TL;DR: As one of the part of book categories, operating systems theory always becomes the most wanted book.
Abstract: If you really want to be smarter, reading can be one of the lots ways to evoke and realize. Many people who like reading will have more knowledge and experiences. Reading can be a way to gain information from economics, politics, science, fiction, literature, religion, and many others. As one of the part of book categories, operating systems theory always becomes the most wanted book. Many people are absolutely searching for this book. It means that many love to read this kind of book.
670 citations
"A case for delay-conscious caching ..." refers methods in this paper
...Subsequently, we test the performance of LNC-R-W3 experimentally and compare it with the performance of other existing cache replacement algorithms, namely LRU and LRU-MIN....
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01 Apr 1995
TL;DR: This paper presents a descriptive statistical summary of the traces of actual executions of NCSA Mosaic, and shows that many characteristics of WWW use can be modelled using power-law distributions, including the distribution of document sizes, the popularity of documents as a function of size, and the Distribution of user requests for documents.
Abstract: The explosion of WWW traffic necessitates an accurate picture of WWW use, and in particular requires a good understanding of client requests for WWW documents. To address this need, we have collected traces of actual executions of NCSA Mosaic, reflecting over half a million user requests for WWW documents. In this paper we present a descriptive statistical summary of the traces we collected, which identifies a number of trends and reference patterns in WWW use. In particular, we show that many characteristics of WWW use can be modelled using power-law distributions, including the distribution of document sizes, the popularity of documents as a function of size, the distribution of user requests for documents, and the number of references to documents as a function of their overall rank in popularity (Zipf''s law). In addition, we show how the power-law distributions derived from our traces can be used to guide system designers interested in caching WWW documents. --- Our client-based traces are available via FTP from http://www.cs.bu.edu/techreports/1995-010-www-client-traces.tar.gz http://www.cs.bu.edu/techreports/1995-010-www-client-traces.a.tar.gz
624 citations
"A case for delay-conscious caching ..." refers background or methods in this paper
...The browsers were temporarily adjusted so that all requests were re-directed to a proxy where for each referenced URL, we recorded the size the of requested document and the difference between the time when the request for document Di arrives at the proxy and the time when Di is actually fetched to…...
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...Several studies of Web reference patterns show that Web clients exhibit a strong preference for accessing small documents [6, 7, 9, 11]....
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...Subsequently, we test the performance of LNC-R-W3 experimentally and compare it with the performance of other existing cache replacement algorithms, namely LRU and LRU-MIN....
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18 Jul 1995
TL;DR: This work assesses the potential of proxy servers to cache documents retrieved with the HTTP protocol, and finds that a proxy server really functions as a second level cache, and its hit rate may tend to decline with time after initial loading given a more or less constant set of users.
Abstract: As the number of World-Wide Web users grow, so does the number of connections made to servers. This increases both network load and server load. Caching can reduce both loads by migrating copies of server files closer to the clients that use those files. Caching can either be done at a client or in the network (by a proxy server or gateway). We assess the potential of proxy servers to cache documents retrieved with the HTTP protocol. We monitored traffic corresponding to three types of educational workloads over a one semester period, and used this as input to a cache simulation. Our main findings are (1) that with our workloads a proxy has a 30-50% maximum possible hit rate no matter how it is designed; (2) that when the cache is full and a document is replaced, least recently used (LRU) is a poor policy, but simple variations can dramatically improve hit rate and reduce cache size; (3) that a proxy server really functions as a second level cache, and its hit rate may tend to decline with time after initial loading given a more or less constant set of users; and (4) that certain tuning configuration parameters for a cache may have little benefit.
495 citations
"A case for delay-conscious caching ..." refers methods in this paper
...The trace contains about 20K requests....
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...Subsequently, we test the performance of LNC-R-W3 experimentally and compare it with the performance of other existing cache replacement algorithms, namely LRU and LRU-MIN....
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