My company is required to perform an performance test of the web component of
our application. We would like to simulate 1500 - 6000 concurrent users.
Ideally, a percentage (30-40%) of these users will be active with a simple
task, while the remaining sessions are active.With this load in place, we'd
like to gather metrics for an incoming session performing a specific task.
We'd like to vary to load and gather this metric for each of the load levels.

To-date, we've been trying to use Appication Center Test for this stress
testing. We seem to be having trouble with the generation of the active load
sessions with ACT. How can we generate multiple distinct sessions that are
ACTIVE within a single iteration of a script?

Is ACT the best tool for our testing? Does Microsoft offer tools better
suited for web application stress testing?

Any feedback would be greatly appreciated. Thanks!