Actually BITS is the old thing by now (it's been present in Windows since Windows XP), which only tries to download things in the background by using spare netw

Actually BITS is the old thing by now (it's been present in Windows since Windows XP), which only tries to download things in the background by using spare network bandwidth. I've never actively tested how well this "spare bandwidth detection" actually works, but on the other hand I've also never negatively noticed it, so I guess it might actually be doing its job quite well. On the other hand there is in fact a newer (relatively speaking, given that it's a few years old by now, too) thingy specifically for Windows Update which also tries to use P2P distribution – that one is called DOS. Officially that stands for "Delivery Optimization Service", though personally I rather prefer "Denial of Service service", because when I first encountered I immediately noticed it in a negative way: Even without any P2P features enabled, it spammed literally dozens of TCP connections to download stuff, and would thereby effectively monopolise the whole bandwidth of my internet connection. Until I figured out what was happening and disabled it (you can disable it and switch back to using BITS for downloading updates), every time my new (at the time) laptop was downloading updates, it would dramatically slow down Internet speeds for everything else in my whole home. Maybe by now that kind of issues have been fixed, but I've never tried it myself because BITS is, as I said, working perfectly fine and unobtrusively.