I want a strange one. Priority management of network access at the application level within the same system

Sometimes strange desires arise. Now I want to find some application that would allow me to set priority on network access for programs running on my computer.

The goal that I want to achieve with such a program is quite simple and I will explain it with an example. Imagine that µTorrent is launched at me and, biting hard at the channel, downloads ... well, let's say, a fresh Debian image. Shakes so that the entire channel for downloading and picks up. At the same time, Thunderbird was launched, which once again checks the mailboxes and stumbles upon an immense letter with important documents on the work. And µTorrent and Thunderbird begin to fight for the channel outside, and no one is going to concede: both the first and second are trying to get the most out of what is available to them. As a result, the speed is shared, do not understand, as you have to wait for document loading due to the fact that the image is not such an important movie .

But if there was a priority management system that I’m dreaming about, then it would be possible to configure in it that µTorrent can wait for data to be transmitted / received if something happens (i.e. it has a low priority), but Thunderbird doesn’t wait should and if necessary, the entire available channel should be provided to him (maximum priority).

Perhaps such a system already exists and is even available in the form of freeware or even open source (plus it is also functional in Windows Vista), but I don’t know what to look for and where on Google. Therefore, I will be happy with any tips, well, or a tub of cold water on my head, so I dream less.