On Distributed Communications Series

XI. Summary Overview

II. Disadvantages of the Distributed Adaptive Message Block Network

  1. The system concept is difficult to explain and to comprehend. (ODC-I, -III, -VII, -VIII)
  2. There is an almost fixed 0.5-sec time delay in voice transmission. (ODC-III, -VIII)
  3. A small distributed network is a meaningless entity--only large networks are capable of emulating the system's desired properties. (ODC-I, -II)
  4. No one has ever built or even fully designed all the hardware components required. (ODC-VII, -VIII)
  5. It is an expensive system to simulate. (ODC-II, -III, -VIII)
  6. The concept is especially sensitive to poor system design. A brute-force, massive-organization approach can easily end up with an expensive, fractional-GNP-priced kluge. (ODC-VII, -VIII, -X)
  7. An understanding of digital computer design is mandatory to adequately evaluate feasibility. (ODC-VII, -VIII)
  8. The cryptographic features have not yet been reviewed by those well-versed in the secrecy business and responsible for determining the acceptability of the proposed generalized secrecy arrangements. The analyses made on secrecy have been limited to information found in the open literature (plus a little common sense). (ODC-IX)
  9. Analog-to-digital conversion is required. (While such transformation is apparently necessary in conventional cryptography, its present cost is high.)
  10. The distributed system, at this time, is designed primarily for communications among large key military installations wherein it is possible to maintain secure areas for cryptographic material adjacent to the Multiplexing Stations. A later logical step in the development of the overall approach is to extend cryptographic protection to remote telephones, a facility not included in the present design. (Some preliminary work has been started on this problem.)
  11. Another possible difficulty is that our present voice telephone plant usually provides excellent service for peacetime civilian communications, and the need for special communications capabilities for the military has not always been widely appreciated. Many tend to evaluate potential performance under combat conditions from the standards of their own civilian voice telephone experience. This is not the best measure for realistically determining the suitability of a military communications system.

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