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The online ad industry might be wise to pay attention to a new proposal for dealing with the problem of cacheing on the Internet.

The Internet Engineering Task Force, a standards body, this week will discuss a draft proposal for a system that would enable Web sites to report the number of times cached pages and ad images are shown to users. Currently, no ad tracking software can do this.

Many large companies and online service providers-notably America Online-use proxy servers within their networks to reduce congestion. When one user visits a Web page, the images and other files are copied onto the proxy server in a so-called cache. When subsequent visitors within that organization visit the same Web page, the files are served from the proxy's cache instead of across the entire network again.


Cacheing has been a bugaboo because it prevents Internet publishers and marketers from knowing exactly how many people are visiting their sites. Some estimate as much as 25% to 40% of all ad impressions are uncounted due to caches, although others say those figures are blind guesses.

"If [proxy servers] are caching a significant amount [of im-pressions], it's holding the Web hostage, revenue-wise. If you can't count it, you can't charge for it," said Kate Everett-Thorp, VP of crusader and advertiser programs at CNET: The Computer Network.

Online publishers use a number of techniques to avoid letting proxy servers cache their ads, a practice known as "cache-busting." While cache-busting allows them to track their ads-and therefore get paid for them-it defeats the goal of cacheing, which is to reduce Internet traffic and speed the end-user experience.


The new proposal by a working group of the IETF seeks to limit cache-busting by providing a basic means of accounting for cached ad impressions. Proxies will be able to report back reasonable estimates of how many "hits" occurred for a given ad or other object.

"The goal of the draft is definitely not a 100% solution," said Kevin Yim, a product manager for

AOL may address cache concerns

the Microsoft Proxy Server who is familiar with the proposed standard (

A more detailed approach to the problem, he said, would create significant debate among the parties affected by the issue. The proposal has been in draft for more than six months, and it could still be months more before products ship to meet the standard.

Mr. Yim wouldn't comment on whether Microsoft would soon implement elements of the standard in its proxy server, but since another Microsoft executive is co-author of the proposal, it seems a safe bet the company is a backer.


Meanwhile, Charles Landau, a product manager for the Netscape Proxy Server said, "We think it's a good proposal, so it's something you could expect us to support in a future release."

Perhaps the biggest source of frustration for Web advertisers is AOL, which widely employs cacheing. Much of its 8 million users' Web usage goes unreported.

"We're working on that problem . . . [of] how to give [advertisers] an idea of what their total audience is in a way that's efficient for everybody and helps the whole industry," said Myer Berlow, AOL senior VP-interactive marketing.

Asked for clarification, an AOL spokeswoman said, "We don't have any plans to make that [ad impression count] information available to the public."

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