For a long time the answer was to throttle downloads as others have said; however today the solution is to use uTP (https://en.wikipedia.org/wiki/Micro_Transpor

For a long time the answer was to throttle downloads as others have said; however today the solution is to use uTP (https://en.wikipedia.org/wiki/Micro_Transport_Protocol https://en.wikipedia.org/wiki/Micro_Transport_Protocol), which is specifically designed to yield to other applications that want better interactivity. Pretty much any recent bittorrent software implements it.