Best approach to monitoring debated

If you want to buy a Web application performance management tool, do you choose one that uses an active or a passive approach?

This gets to the heart of what Computer Associates International Inc.'s Unicenter brand manager Bob Ure called the "holy war" in the tools world. On one hand, the active approach, in which simulated transactions are spawned and sent through a system periodically as a proxy for the end user, allows organizations to get a detailed look from the users' perspective of how Web-based applications work.

However, Ure said, active monitoring does add overhead to the network and doesn't provide much detail about why things slow down.

"That's where passive monitoring comes in," he said, because it can watch at various points in the network for the response times of applications without affecting the flow of traffic.

In reality, you need a mix of both passive and active tools to get a detailed look at what's happening to Web applications, said Mike Magri, NetQoS Inc.'s product manager for SuperAgent, a passive, server-side application response monitor. "But if I were competing for the same customer's dollars, I would say every time that passive is better than active," he said.

An active probe is necessary to see if such things as a registration transaction are working correctly for a particular Web application, he said, but that's useless when thousands of registrations are being logged at any given time. "Then you need a passive solution if you want to get an idea of what the traffic is like for all possible locations," Magri said.

It would be great to have both active and passive solutions, agreed Dave MacRae, senior director for business strategy and development for Smartronix Inc., a network engineering firm that uses NetScout Systems Inc.'s nGenius probes, but the passive approach can gather as much as 97 percent of the traffic moving through various sites "and with that level of detail, you can do many different things" in performance management," he said.

Robinson is a freelance journalist based in Portland, Ore. He can be reached at hullite@mindspring.com.