Very long "Waiting to transmit the response" times shown in profiler
I encountered an issue where I was getting really slow performance from a server, and I ruled out the server's query as being the issue. I ran the performance profiler, and I found that virtually all of the time was spent in the "Waiting to transmit the response" phase, found in the Network tab of the profile, when hovering over a long bar. In many cases, it was taking over 15 seconds, and there wasn't much information at all being sent from the server.
My question is, what exactly does that phase of the request cover? Could it involve the server not sending data fast enough? A network issue (DNS, proxies, etc.)? The client being low on resources at that moment?
Also, can someone please provide me a list of possible other areas of the profile, or anywhere else, to check to help me narrow down the cause of slow performance in this specific area?