If my load generators are in some remote location (not on the network)..how do I specify that in the controller. Say controller is in boston and the load generators are in Sanfrancisco and Newyork, how do I tell the controller to use these generators?
By Hostname... (assuming hostnames resolve from generator to host, host to generator and generator to target)
You may be wise to consider testing on a restricted testbed first, to ensure that your app scales with the smallest network possible, or the alternative is place a small number of "control" virtual users of each type on a load generator right next to your host under load. Watch the response time from your control group compared to your global population. If your uncontrolled group begins to degrade at a faster rate than your controlled group, then you have a network issue which is impacting your response times to a greater degree than your application.
It is better that you find this than have this come out in a meeting when the application group and the network group are both pointing fingers at each other over who is at fault for the long response times.