A local area network employs a shared control channel over which control messages between frequency agile modems for each of the user nodes of a distributed architecture-configured network are exchanged. In addition to the shared control channel, a plurality of data channel pairs is available for effecting full duplex communications between any two nodes of the network. Because all data channel assignments depend upon successful use of the control channel, a prescribed control channel contention access scheme is employed to optimize use of the control channel by all users of the network irrespective of the demand for its use. Pursuant to this scheme, each requesting node must first compare an accumulated activity measure with a traffic density threshold that is continuously optimized for the current level of control channel activity. Unless the accumulated measure is less than the threshold, the requesting user node is temporarily forbidden access to the control channel by a period of time designed to reduce traffic to the optimal level.