University of California, Santa Barbara (UCSB) The network program at a site must be prepared to send or receive more than one control message in a single control communication. During the time that the control link is blocked awaiting RFNM, it is possible that a number of control messages to a particular remote host will accumulate. When the link is unblocked, these should all be sent in a single communication for greatest efficiency. For receiving, it will be necessary to have a loop which returns to decode and take action on successive control messages until the control communication is exhausted.