In a previous life we had a unique challenge to monitor a client environment to try and determine under-provisioned circuits. We used custom bandwidth settings on all of the external interfaces and then built an alert that checked for sustained latency without either upload or download utilization > 80%. This wasn't a fool-proof alert and still required some triage on our side to see if the problem was legitimate but it worked. Having those alerts and being able to back up our claims with data definitely helped when we had to go to the service providers and tell them that they had under-provisioned a circuit.
He who has the most convincing data wins!
Of course, now that NPM has QoE via DPI that changes the game, especially for companies that host custom applications on a Windows platform. We can get super-specific about whether that squeaky wheel needs to have network or application resources applied instead of hauling in a room full of people.
