June 21, 2024

ARPANET and Systems Thinking


Important points were raised at the design stage of ARPANET:

  • Systems thinking was applied to the task by BBN's designers. They realised that the network would inevitably fall prey to unexpected behaviour. Consequently the designers of both the IMPs and the software would need to be appraised of this thinking.
  • Elaboration in a few key passages of the design meant the need for error correction and adaptive routing.
  • BBN decided not to build facilities for host-to-host (i.e. end-to-end) checking. Wesley Clark's idea of having a reliable sub-network of message switches (IMPs) was to be implemented. Hosts would just to talk to their local IMP. BBN thought this was necessary if ARPANET was to be delivered on time. However, this design philosophy required change when ARPANET was moved across to form part of the Internet.

Kahn had serious concerns about the proposed network.
What if every node functioned perfectly, but the network still failed? ARPANET was a system. The behaviour of the whole cannot necessarily be inferred from the behaviour of its individual components. "The whole is greater than the sum of its parts", but "the whole can be less than the sum of its parts". Systems thinking takes a holistic view.

What is a system?

  • The components of a system are connected together in an organised way - structure is crucial.
  • Components are affected by being in the system and are changed if they leave it. Components cannot be considered in isolation if the behaviour of the system is to be predicted. This idea is linked to the concept of emergent behaviour, which arises from the interactions of the components. Systems are dynamic.
  • The structure carries out a task; it exhibits dynamic behaviour. It fulfils a function or serves some purpose, although that purpose may be open to interpretation.
  • Technological systems, and hence their structures, are devised by humans, with the consequences of being imbued with subjective perceptions of reality.

Why is systems thinking needed?

  • Real-world phenomena are often extremely complex and can only be understood by looking at them in systems terms.
  • Decisions to intervene sometimes lead to unintended consequences.
  • Technical infrastructure of Western society requires the construction, maintenance and development of complex systems.

What is involved in systems thinking?

Thinking systemically, that is pertaining to a system, is not the same as thinking systematically, which means having a method or a plan. Humans are conditioned to view aspects of the world in isolation. This is a reductionist view and typical of traditional scientific thought. Reductionist thinking does not consider whole-system behaviour, that is the holistic view. Humans tend to analyse in cause-effect terms, considering a particular effect to be linked to a single cause. The interconnected nature of dynamic systems means that behaviour is influenced by multiple causes.

Systems thinking involves :

  • Focusing on whole and emergent properties, rather than individual components.
  • Studying the interaction between components. How do the components fit together? This is an example of synthesis as opposed to a reductionist analysis of components.
  • Looking at systems from differing perspectives by constructing partial views.


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