Analyzing packets at two points provides an accurate way to determine the delays across a network. The team at Advance7 used this technique to find the cause of performance and stability problems with a web application. The system topology was complex, but very common in today's enterprise environments; users accessing systems using a Windows terminal and ESX VDI-delivered desktops.
Users reported slow response times and intermittent disconnects. The path through the network from VDI host to application server was 10 GbE all the way, and so link overload was unlikely. There were various theories about the cause of the problem but the Advance7 team needed to produce some solid evidence.
This is how they did it - https://community.tribelab.com/mod/page/view.php?id=682