Ad insertion at proxies to improve cache hit rates Amit Gupta and Geoffrey baehr, Sun Microsystems Laboratories 901 San Antonio Road Palo Alto,CA 元智資工所 系統實驗室 楊錫謦 1999/7/20

Outline: Background Design choices The LocalAd system and Performance Conclusion

Background: Web caching reduces the advertising revenues that the content providers generate Cache-busting increases the advertising revenues,but it negates all the benefits of web caching The revenues can be shared between the content provider and the local station by using a model similar to television and radio network

Design choices: 1. Design goals - Compatibility - Efficiency - Flexibility 2. Identifying the ad-insertion position problems - corrupt the HTML layout increase computational load copyright

3. When to insert ads “Early insertion” -- Insert ad before the server returns the HTML codes for the URL that the client request 4. Proxy-server protocol Proxies should add an extra header in the HTTP REQUEST message to indicate their interest in local ad insertion

Three alternatives for communication from the server to the proxy: 1. Maintain full compatibility with current schemes: ex: 2. New HTML tags 3. New HTTP headers

5. Revenue-sharing The content-provider can place a price tag on the advertisement slot. If the proxy replaces the ad, it must pay that price to the content-provider. The content-provider are free to vary the price on a per HTTP request basis, while the proxies are equally free to accept these price, or reject them.

The LocalAd system & performance: 1. System components a. Customer database b. Logger c. Profiler d. Ad manager e. Ad replacement engine 2. Performance User latency go up by 1-2ms

HTTP request Proxy Server Customer manager Profiler Logger Ad replacement engine Ad manager Modified page

Basic rules that the chained proxy should follow A proxy can add the LocalAd-interest header to the HTTP request if no such header exists A proxy can put in a new price tag on the replaced ad A proxy should avoid that a software flaw corrupts the HTML stream

Conclusion: Collaboration between content-provider and the proxy servers improves cache hit rates by addr- essing cache-busting with economic incentives for all concerned parties The authors are currently exploring the issues in applying the LocalAd approach to the more general problem: dynamic content rewriting