How can i make my internet connection faster for my xbox 360?

i have 2 routers, and my xbox is wired connection.. when i connect to the modem i can play with my best friend, but when i used a router i cannot. why? my routers are.....Netgear WGR614 v9..... and ........(CISCO) Linksys wireless-N home router model # WRT120N... can somone help me to try to connect to my friend with a router?