RVP Control Protocol (RVPCP)
The control protocol was initially developed for point-to-point data applications like the control messages that configure and maintain the data link between the client and the server. During an RVP/IP session, only one class of RVP/IP control message is exchanged: RVPCP ADD VOICE (operation code 12) packet which is used to send the UDP port used by the client (for subsequent voice data packets) to the server. This message always takes a single parameter of type RVPCP UDP PORT (type code 9), which always has a length of exactly two and a value that is the two-byte UDP port to which voice data packets should be addressed.
[para]The server responds with a packet containing the code RVPCP ADD VOICE ACK (operation code 13) which contains exactly one parameter, the server's voice UDP port. If RVP/IP is operating in "dynamic voice" mode, this exchange must be repeated whenever the voice channel needs to be reestablished, i.e., whenever the phone goes off-hook. Most of the functionality of this protocol is unnecessary when using TCP/IP.