M. C. Chan and T. W. C. Woo. Cache-Based Compaction: A New Technique for Optimizing Web Transfer. In 453 Proceedings of INFOCOM-1999.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....sizes for the transmitted deltas. However, these schemes are only applicable to a minority of page accesses, and require web or proxy servers to retain potentially many different outdated versions of pages for use as reference files in the encoding. Another approach, studied by Chan and Woo [4], encodes a page with respect to similar files located on the same web server that are already in the client s browser cache. Based on the latter approach, we study different delta compression policies for web access. Our emphasis is on web and proxy server friendly policies that do not require ....

....9] Xdelta [10] and zdelta [16] are freely available. We refer to [15] for an overview of delta compression techniques and their applications. 1. 1 Delta Compression for Web Access A number of authors have proposed the use of delta compression techniques to improve the efficiency of web access [1, 4, 6, 7, 11, 12, 18]. In particular, when web pages are updated, they typically do not change by much, and thus delta compression can be used to very succinctly encode the difference between a new version of a web page and an outdated version already in the client s browser cache. Most proposals focus on encodings ....

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M. Chan and T. Woo. Cache-based compaction: A new technique for optimizing web transfer. In Proc. of INFOCOM'99, March 1999.

....appropriate for clients connected via low bandwidth links such as cellular modems. It has also been observed that web pages on the same server often have a high degree of similarity (due to common layout and menu structure) that could be exploited with delta compression techniques. In particular, [13] proposes to identify candidate pages that are likely to be good reference files for delta compression by looking for URLs that share a long common prefix with the requested one. Other work [19] proposes a similar idea for dynamic pages, e.g. different stock quotes from a financial site, that ....

....in this case. If we also plan to exploit similarities between different pages, then the problem of selecting appropriate reference pages arises. While the general formulation of this problem, discussed further below, is quite challenging, specialized techniques based on URL prefix matching [13] plus separate detection of mirrors [9] and replicated collections [15] may suffice in practice. 2.2 Fundamentals Recall that in the delta compression problem, we have two files, 386 and , and the goal is to compute a file of minimum size, such that one can reconstruct from 44 ....

[Article contains additional citation context not shown here]

M. Chan and T. Woo. Cache-based compaction: A new technique for optimizing web transfer. In Proc. of INFOCOM'99, March 1999.

....of magnitude smaller than the compressed target file. Delta compression techniques have also been studied in detail in the context of the World Wide Web, where consecutive versions of a web page often differ only slightly [8, 19] and pages on the same site share a lot of common HTML structure [5]. In particular, work in [2, 5, 7, 11, 18] considers possible improvements to HTTP caching based on sending a delta with respect to a previous version of the page, or another similar page, that is already located in a client or proxy cache. In this paper, we study the use of delta compression in ....

....the compressed target file. Delta compression techniques have also been studied in detail in the context of the World Wide Web, where consecutive versions of a web page often differ only slightly [8, 19] and pages on the same site share a lot of common HTML structure [5] In particular, work in [2, 5, 7, 11, 18] considers possible improvements to HTTP caching based on sending a delta with respect to a previous version of the page, or another similar page, that is already located in a client or proxy cache. In this paper, we study the use of delta compression in a slightly different scenario. While in ....

[Article contains additional citation context not shown here]

M. Chan and T. Woo. Cache-based compaction: A new technique for optimizing web transfer. In Proc. of INFOCOM'99, March 1999.

....patches, one can significantly reduce network traffic. Delta compression could also be used to improve HTTP performance. By exploiting the similarity between different pages on a given website or between the different versions of a given web page, one can reduce the latency for web access [1, 2, 3]. The zdelta tool, presented in this paper, is fairly general and could be efficiently used in any of these applications. The organization of this paper is as follows: Section 2 contains a brief survey of different delta techniques and of available delta compression tools. Section 3 provides a ....

....of the various parts of the file. A similar idea could be added to zdelta to obtain better compression in certain cases. Another natural extension would be to allow compression of one data set in terms of two or more reference data sets. For the case of web pages from a common server, work in [2] shows that there can be significant benefit in using to reference data sets. Finally, the problem of identifying suitable reference files in a collection of files is an interesting problem; see, e.g. the discussion in [7] ....

M. Chan and T. Woo. Cache-based compaction: A new technique for optimizing web transfer. In Proc. of INFOCOM'99, March 1999.

....of magnitude smaller than the compressed target file. Delta compression techniques have also been studied in detail in the context of the World Wide Web, where consecutive versions of a web page often differ only slightly [8, 19] and pages on the same site share a lot of common HTML structure [5]. In particular, work in [2, 5, 7, 11, 18] considers possible improvements to HTTP caching based on sending a delta with respect to a previous version of the page, or another similar page, that is already located in a client or proxy cache. In this paper, we study the use of delta compression in ....

....the compressed target file. Delta compression techniques have also been studied in detail in the context of the World Wide Web, where consecutive versions of a web page often differ only slightly [8, 19] and pages on the same site share a lot of common HTML structure [5] In particular, work in [2, 5, 7, 11, 18] considers possible improvements to HTTP caching based on sending a delta with respect to a previous version of the page, or another similar page, that is already located in a client or proxy cache. In this paper, we study the use of delta compression in a slightly different scenario. While in ....

[Article contains additional citation context not shown here]

M. Chan and T. Woo. Cache-based compaction: A new technique for optimizing web transfer. In Proc. of INFOCOM'99, March 1999.

....control devices, and cellular devices. The data contents of these devices are often updated by transmitting the new version over a network. However, low bandwidth channels and heavy Internet traffic often makes the time to perform software update prohibitive. Differential or delta compression [3, 13, 9, 8], encoding a new version of a file compactly as a set of changes from a previous version, reduces the size of the transmitted file and, consequently, the time to perform software update. Currently, decompressing delta encoded files requires scratch space, additional disk or memory storage, used to ....

....performed this task using time quadratic in the length of the input files. Delta compression algorithms were improved to run in linear time and linear space. Algorithms with these properties have been derived from suffix trees [27, 18, 16] and as a generalization of Lempel Ziv data compression [12, 13, 8]. Like algorithms based on greedy methods and dynamic programming, these algorithms generate optimally compact delta encodings. Recent advances produced algorithms that run in linear time and constant space [3] These differencing algorithms trade a small amount of compression, verified ....

M. Chan and T. Woo. Cache-based compaction: A new technique for optimizing web transfer. In Proceedings of the IEEE Infocom '99 Conference, New York, NY, March 1999.

....turned out to create extremely complex rules for handling entity tags and cache entries. We also found it difficult to define how a client could ask for delta encoding, ranges, and compression in various orders. Other proposed HTTP extensions, such as rsync[31] and cachebased compaction[4], share the definitional problems first seen with delta encoding. We can visualize the situation by depicting the HTTP message generation model as a pipeline, as shown in figure 1(a) In this figure, datatypes (bold faced terms) are transformed via processing steps (arrows) such as variant ....

M. C. Chan and T. Woo. Cache-based compaction: A new technique for optimizing Web transfer. In Proc. IEEE Infocom '99, pages 117--125, New York, NY, March 1999.

....sublinear asymptotic space bound is presented. Based on the description of this algorithm in [12] it appears to use space proportional to the length of the reference string if the reference string is not compressible, even when the reference and version strings are highly correlated. Chan and Woo [5] describe an algorithm that encodes a file as a set of changes from many similar files (multiple reference versions) using a similar technique. These algorithms have the advantage that substrings to be copied may be found in the version string as well as the reference string. However, most ....

M. Chan and T. Woo. Cache-based compaction: A new technique for optimizing web transfer. In Proceedings of the IEEE Infocom '99 Conference, New York, NY, March 1999.

....Then it can generate new pages based on modular and differential page construction techniques. For example, delta encoding [2] 3] combines the data already in cache with any differential updates from the origin server. Other techniques include partial transfers, cache based compaction [4], and HTML macros [5] In the second case, Gemini supports on the fly page construction by running publisher authored code for filtering and versioning, etc. Consider the application of filtering to the dynamic generation of customized news pages (e.g. MyYahoo) The publisher code residing at ....

M.C. Chan and T. Woo, "Cache-based compaction: A new technique for optimizing web transfer," in Proceedings of IEEE INFOCOM'99, 1999.

....hint allowing a server to indicate which versions should be retained by the client and for how long. The speci cation also suggest the use of instance digests for integrity checking [33] and VCDIFF, a proposed communication format based on Vdelta, for delta encoding [27] A system by Chan and Woo [8] uses two techniques to optimize web transfer. It has no conceptual family identi er; instead it uses a selection algorithm for choosing objects from a cache that are likely to be similar based on a measure of path structure similarity. This is based on the observation that web sites often use a ....

Chan, M. C., and Woo, T. Cache-based compaction: A new technique for optimizing Web transfer. In Proceedings of the INFOCOM '99 conference (Mar. 1999).

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M. C. Chan and T. W. C. Woo. Cache-Based Compaction: A New Technique for Optimizing Web Transfer. In 453 Proceedings of INFOCOM-1999.

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CHAN, M. C., AND WOO, T. Cache-based compaction: A new technique for optimizing Web transfer. In Proceedings of the INFOCOM '99 conference (Mar. 1999).

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M. C. Chan and T. W. C. Woo. Cache-Based Compaction: A New Technique for Optimizing Web Transfer. In Proceedings of INFOCOM-1999.

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M. Chan and T. Woo. Cache-based compaction: A new technique for optimizing web transfer. In Proc. of INFOCOM '99, March 1999.

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