It's not easy to know how well a public-facing Web application is performing for end users. There are just too many blind spots along Internet pathways. At the same time, it's critical for businesses to ensure customers are experiencing acceptable application response times. If a site is too slow, it won't be long before customers defect to a competitor.

To help businesses get an accurate picture of the end-user experience, Internet testing vendor Gomez has been building out a network of real users’ PCs, which it uses to test and measure Web-site performance. To date the company has 45,000 peers in its network, spread across 154 countries and representing a range of connection speeds and ISPs.

The peers provide a view into real-world Internet conditions that companies can’t get from traditional data center testing of new or revamped Web applications, says Imad Mouline, CTO at Gomez. With the popularity of Web services-based applications and third-party application providers, very few applications today are completely built and delivered from a single location. If a company is only looking at the parts of an application that reside behind the firewall, it’s not getting the full performance picture, Mouline says. “The only way to truly understand the impact [of deploying a new application] is to test it from that very last mile, where the end users truly are.”

Desktop computers in the peer network are used to run tests that measure the speed, availability and consistency of Web sites. Each peer runs agent software that emulates popular Web browsers and runs testing when the peer machine is online.

Participating end users gain from the program, too: Gomez offers compensation for being a Gomez Peer (see details about signing up here) that can add up to as much as $40 per month.

The peer network feeds data for Gomez’s Active Network XF and Active Last Mile XF Web-site monitoring services and its Reality Load XF external load testing service. Gomez also offers Internet backbone testing services. (Compare application performance monitoring products)

Ann Bednarz is associate news editor at Network World.