RFC 2227 (rfc2227) - Page 2 of 37
Simple Hit-Metering and Usage-Limiting for HTTP
Alternative Format: Original Text Document
RFC 2227 Hit-Metering and Usage-Limiting October 1997 4 Analysis 17 4.1 Approximation accuracy for counting users 18 4.2 What about "Network Computers"? 19 4.3 Critical-path delay analysis 19 5 Specification 20 5.1 Specification of Meter header and directives 20 5.2 Abbreviations for Meter directives 23 5.3 Counting rules 24 5.3.1 Counting rules for hit-metering 24 5.3.2 Counting rules for usage-limiting 25 5.3.3 Equivalent algorithms are allowed 26 5.4 Counting rules: interaction with Range requests 27 5.5 Implementation by non-caching proxies 27 5.6 Implementation by cooperating caches 28 6 Examples 28 6.1 Example of a complete set of exchanges 28 6.2 Protecting against HTTP/1.0 proxies 30 6.3 More elaborate examples 30 7 Interactions with content negotiation 31 7.1 Treatment of responses carrying a Vary header 31 7.2 Interaction with Transparent Content Negotiation 32 8 A Note on Capturing Referrals 32 9 Alternative proposals 33 10 Security Considerations 34 11 Acknowledgments 35 12 References 35 13 Authors' Addresses 36 14 Full Copyright Statement 37 1 Introduction For a variety of reasons, content providers want to be able to collect information on the frequency with which their content is accessed. This desire leads to some of the "cache-busting" done by existing servers. ("Cache-busting" is the use by servers of techniques intended to prevent caching of responses; it is unknown exactly how common this is.) This kind of cache-busting is done not for the purpose of maintaining transparency or security properties, but simply to collect demographic information. Some cache-busting is also done to provide different advertising images to appear on the same page (i.e., each retrieval of the page sees a different ad). This proposal supports a model similar to that of publishers of hard-copy publications: such publishers (try to) report to their advertisers how many people read an issue of a publication at least once; they don't (try to) report how many times a reader re-reads an issue. They do this by counting copies published, and then try to estimate, for their publication, on average how many people read a Mogul & Leach Standards Track
