Say you were using BitTorrent to download and upload your torrent files. In order to create faster speeds you would forward the ports 6881-6889. This "supposedly" gives you speed improvements that seem impossible.
Now that I am on a mac however and using Transmission (which i love the simplicity of) I do not know which ports to forward through my router in order to make necessary speed adjustments. Does anyone know what ports Transmission.app uses? An actual answer would be very helpful.=)