Method of implementing multimedia protocol passing through network address transform device

The invention claims a multimedia protocol is a method for realizing network address translation device, and method is as follows: A private network terminal to with a voltage public network terminal transmission request message obtaining transmission media stream the source address; A private network terminal to the source address transmitting redirection structure, the source address in the redirecting structure and receiving end slogan a private network terminal private network and IP address; The NAT the redirecting comprises source address replacing the public network address transfer the public network terminal, a front and a replacing, the source address and destination address and replacing the redirecting structure, the mapping relationship of source address and destination address in redirecting structure; The public network terminal and a public network address to the destination address transmission media stream, wherein the NAT device switches to the mapping relationship of destination address mapping the media stream the private network address terminal.