Last week I talked a bit about the need -- or the lack thereof -- of agent software to monitor endpoint machines, such as desktops and laptops. This week I am focusing on appliances, installed at various points across a network to capture the critical client, or end-user, experience with applications on desktops and laptops.

"The ultimate judge of IT and business alignment is the end user; If alignment is viewed as conformity to user expectations in terms of availability, usability and accuracy, then monitoring end user performance is the only way IT knows that it is meeting these expectations," writes Jean-Pierre Garbani, a vice president at Forrester Research, in a recent report.

The report Forrester Research recently put out examines examining the market, which includes management heavyweights such as CA as well as innovative newcomers such as Coradiant. The appliance-based end user experience monitoring vendors had similar technical approaches to capturing this critical metric, Forrester found, but the vendors distinctly targeted four specific markets: business marketing, global application performance debugging, Web-based application performance, and Java 2 Enterprise Edition and .Net application management.

To start, Forrester looked at how companies including Adlex (acquired by Compuware), NetQoS, BeatBox (acquired by Mercury Interactive now part of HP), Coradiant and Tealeaf Technology approached the technical challenge of capturing the client experience. In general, the vendors place an appliance loaded with their respective software in a central location. A data collector component connects to a switch and passively monitors traffic and a reporting server aggregates data from one or more data collectors. This method does not require agents on client desktops, which makes sense since if you are measuring the performance of Web applications most companies can't access customer desktops and place an agent there.

"On the downside, this type of configuration does not provide any insight into what happens at the desktop level, nor does it lend itself to all types of applications: Only IP-based protocols are decoded to provide information; many times, even this is restricted to some application-level protocols," the report reads.

Denise Dubie is senior editor with Network World.