u can't
u may only give him 1/4 of ur bandwidth, but even tho he might only have 1/4 of the bandwidth, he can still connect to xxxxxx ppl sending xxx packets and receiving xxx packets at once.... which will still F**Kup ur ping
u might as well drop the router and buy a 100$ computer, put 4 NICs on it, and get something like WinGATE.... and control and allowed simultaneous connections & so on..