document: Aliasing on the world wide web : prevalence and performance implications Aliasing occurs in Web transactions when requests containing different URLs elicit replies containing identical data payloads . Conventional caches associate stored data with URLs and can therefore suffer redundant payload transfers due to aliasing and other causes . Existing research literature , however , says little about the prevalence of aliasing in user-initiated transactions , or about redundant payload transfers in conventional Web cache hierarchies . This paper quantifies the extent of aliasing and the performance impact of URL-indexed cache management using a large client trace from WebTV Networks . Fewer than 5 % of reply payloads are aliased ( referenced via multiple URLs ) but over 54 % of successful transactions involve aliased payloads . Aliased payloads account for under 3.1 % of the trace 's `` working set size '' ( sum of payload sizes ) but over 36 % of bytes transferred . For the WebTV workload , roughly 10 % of payload transfers to browser caches and 23 % of payload transfers to a shared proxy are redundant , assuming infinite-capacity conventional caches . Our analysis of a large proxy trace from Compaq Corporation yields similar results.URL-indexed caching does not entirely explain the large number of redundant proxy-to-browser payload transfers previously reported in the WebTV system . We consider other possible causes of redundant transfers ( e.g. , reply metadata and browser cache management policies ) and discuss a simple hop-by-hop protocol extension that completely eliminates all redundant transfers , regardless of cause .
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