and again here
http://gafferongames.com/networking-for-game-programmers/udp-vs-tcp/
though Glenn says that "My recommendation then is not only that you use UDP, but that you only use UDP. Don’t mix TCP and UDP, instead learn how to implement the specific pieces of TCP that you wish to use inside your own custom UDP based protocol."
Later in the comments he replies about mixing the protocols that "now, of course if you just had the occasional event sent via TCP, and the bulk of your time sensitive data in UDP, no problems at all"