On Distributed Communications Series

XI. Summary Overview

III. Some Positive Attributes of the Distributed Adaptive Message Block Network

  1. The system uses automatic learning to obtain "perfect switching"[1] in its fully-distributed network con-figuration. Thus, it is less vulnerable to enemy attack than conventional networks. (ODC-I, -II, -III)
  2. The system has been designed completely from scratch to meet future requirements of military security, physical survivability, digital data flexibility, and ease of adding new services. (ODC-I, -IV, -V, -VIII, -IX)
  3. The system handles start-stop teletype, as well as standard "high-speed" binary-stream synchronous data rates of 600, 2400, 4800, 9600, and 19,800 bits/sec. It could easily be adapted to handle very-high-speed data, if required. (ODC-VIII)
  4. Each of the up to 1024 Multiplexing Stations simultaneously handles some 128 cryptographically-secure telephone subscribers, together with 866 other simultaneous subscribers using other data input devices. (ODC-VIII, -IX)
  5. Automatic user-to-user cryptography is integrated into the network switching apparatus to eliminate the need for slow, manual cryptographic synchronization. (ODC-VII, -VIII, -IX)
  6. User-to-user information flows through the network only during actual transmission of information. For example, after a "pseudo-circuit" is established, blank spots lasting longer than 1/20 sec in speech modes are not transmitted. Thus, high-quality speech need only load the transmission plant to an average equivalent data rate of about 5000 bits/sec. (ODC-VIII)
  7. The system is readily amenable to the use of satellites as links. (ODC-VII)
  8. The system is able to withstand heavy network damage without interruption of on-going, end-to-end traffic. (ODC-I, -II, -III, -IX)
  9. From the user's viewpoint, the system appears to be virtually noise- and error-free when handling data. (ODC-VIII, -IX)
  10. No cumulative distortion occurs on voice circuits (whether 1 mi or 10,000 mi long) other than a fixed initial quantization noise. (ODC-III, -VIII, -IX)
  11. Undetected digital errors are expected to be extremely rare. (ODC-III, -VIII, -IX)
  12. The network is designed to handle a broad mixture of input/output devices. (ODC-III, -VIII, -IX)
  13. Automatic error detection and repeat transmission is built into the system on a link-by-link basis, simplifying the design of highly automated, low-cost digital input devices. (ODC-I, -VII)
  14. Multi-level cryptography and automatic errortracking procedures make the system far more immune to sophisticated sabotage than any other known communications system. (ODC-VII, -VIII, -IX)
  15. Instantaneous, multi-station, cryptographicallysecure conference calls can be set up even after the conversation is underway. (ODC-VIII)
  16. The potentially high degree of security protection provided permits a mixing of classified and unclassified traffic, both military and civilian, over the same facilities. (ODC-VII, -VIII, -IX)
  17. As Message Blocks usually travel by different routes, it appears impossible for an eavesdropper to decrypt traffic unless all preceding Message Blocks are received. (ODC-II, -III, -VIII, -IX)
  18. The system appears to be highly resistant to overload--even when subjected to heavy damage. (ODC-V)
  19. The overall system reliability offers hopes of being far better than today's systems; and, it can be built of elements of lower-reliability than presently used. (ODC-I, -III, -VII, -X)
  20. The system uses regenerative (saturated) amplification to circumvent the effects of cumulative distortion, thereby permitting the use of inexpensive, high-data-rate links. (ODC-VIII, -X)
  21. The system uses the "mini-cost" microwave to build new high-data-rate links at very low cost; 4.5-megabit/sec rates appear feasible at a link cost a decimal order of magnitude lower than in conventional systems. (ODC-VI)
  22. Cost, even on a per-subscriber basis, appears roughly comparable to that of present-day conventional networks. (ODC-VIII, -X)
  23. Signaling symbols are transmitted as repetitive binary patterns at the same bit rate as the data information, permitting additional signaling, if desired, while the receiver is "off-hook." This feature can be used to simplify future automatic computer-to-computer conversation. (ODC-VIII)
  24. Automatic error detection and analysis is easily implemented by virtue of the all-digital nature of the equipment, facilitating the locating of possible sources of trouble. (ODC-VII, -IX)
  25. This system has the security, speed, and low-error characteristics to make it useful as a signaling network to set circuit switches for possible extremely-high-data-rate circuit-switched systems in the far future.
  26. The system allows ready implementation of sophisticated automatic priority, precedence, and overload controls. (ODC-IV)

[1] See ODC-IV, p. 12.

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