Ad serving platforms drive a lot of web site revenue. These software platforms grant a site manager control over local or remote ads appearing on his web site. Over the years these platforms grew in functionality and today they offer diverse functions such as:

• Reporting ad statistics on clicks and other activities related to ads.
• Targeting ads to specific users based on their profile or past browsing.
• Sequencing ads to create an evolving message for the user.
• Limiting how many times an ad is seen by a specific user.

Growth in features and scale takes its toll. As ad serving platforms offer new, ever more complex features—they become vulnerable to scaling issues. A feature rich platform that could cater to hundreds or thousands of clients grinds to a halt when exposed to significantly higher traffic volume. This is especially painful for remote ad servers who server content across domains. Performance issues on such a platform can take down the ads on dozens of different sites, causing massive loss of revenues to the site and the platform owners.

Solving the problem of feature growth and scale is not simple. The obvious course of action is to invest heavily in QA, performing exhaustive testing of new features under the kinds of load it will experience in the field. But even when using the best QA methods and investing heavily in such activities, there will always be bugs that slip by the net, bugs that could take down your entire ad serving infrastructure.

Application Delivery Controllers (ADC) can offer a safety net for such occurrences. Assume that your sophisticated ad serving platform is experiencing severe delays due to some unexpected load or bug. The browsers will experience time outs when fetching ads making the web page unsightly and ineffective as far as ecommerce goes. But what if you could detect such a state (even if it is brief) and instead of serving your super intelligent targeted ad, just serve a simple, common one. That way your ad campaign may be less effective but it will not ruin the customer’s surfing experience. An ADC sits exactly in the right spot for doing just that. By monitoring the time it takes the server to dish out a response, it can intervene and send out a pre-designed ad if the server is too slow to respond.

Of course not all ADCs are made equal. In order to monitor tens of thousands of requests simultaneously and take a decision with a resolution of few milliseconds would require a machine that relies on hardware instead of software.