On Distributed Communications Series
IV. Priority, Precedence, and Overload
A precedence system which is time-dynamic in operation has been proposed. The assignment of capacity and capability is designed to be rapidly changed by the military communications controller. The goal sought is to automate those procedures which help a communications network overload gracefully under attack. The priority order is generally consistent with present military precedence concepts except that means are included to encourage the use of lower-data-rate generating devices in preference to the high-data-rate generating devices in times of overload.
While we have discussed only hard-copy messages, the same mechanisms appear suitable for telephone calls. The feedback information that the called party will not be able to answer within a prescribed period can be announced by an easily recognizable tone pattern. Such signaling tones at the beginning, at the mid-point, and near the end of such rationed calls should also serve to shorten their length. Similar tones could also indicate that the calling party is working against an incoming backlog, and could indicate the urgency of that backlog. All the information needed to implement such a seemingly complex precedence system is available at the Multiplexing Station (see ODC-VIII) in the Distributed Adaptive Message Block Network.
While the techniques discussed best lend themselves to an all-digital distributed network, the general notions apply in any situation where volume-limited communications is found. We feel that a usable priority structure might one day be evolved that can be implemented on a semi-automatic basis without extreme, continuing demands on executive judgment.
The communications control system suggested seeks to implement the law of management by exception. Each person has a certain job that he must do; as long as he is able to operate within organizational constraints, it is not necessary to request help from a higher hierarchical level. If the demand exceeds capability, only exceptional cases need be transmitted to a higher level for action.
In the proposed control system, changes in network loading are spotted and displayed to predict that a reconstruction of allocation of the communication resource may soon be required. If the commander concurs, he can instantly re-allocate his available resource among the many demanders for the resource without complete deprivation to any.
We seek to reduce the inflationary struggle for priority treatment of messages by the generators of communications far down the hierarchical chain. These sources are the sensors which perceive some of the most important information in need of transmission in a crisis. At present, these individuals do not always have the authority to obtain immediate precedence treatment for their messages without a serial series of approvals before a person is reached who has enough authority to place urgent traffic in the network. We think we can do better.