I’m not sure what the Unity downloader/installer is doing exactly, but while it’s downloading, it basically causes every other network connection on my machine to fail… the browser slows to a crawl, apps all say they’ve been disconnected from the network, Windows services spam the error log, etc. Are you guys doing some kind of trick where you open like a hundred simultaneous threads with different TCP ports going to try to speed up downloading? If so, could you ease back a bit? I know downloading fast is nice and all, but starving the TCP ports for all other services to try to eke out an extra few bits per second is quite rude. 
Have you tried running netstat from a command prompt? You could see exactly how many ports its using.