A friend and I were studying for a network test and we came up with a question we couldn't completely answer. Since you can't assign a port once you already have it assigned how does something like a DNS transfer work since DNS normally uses port 53 with UDP, what happens when a zone transfer takes place and it wants to use TCP 53? Do you have to shutdown the DNS response to queries so that you free up port 53 for the zone transfer? If not how can you use port 53 for a UDP connections and TCP connection simultaneously on the same server? Thank you