65 lines
2.8 KiB
Markdown
65 lines
2.8 KiB
Markdown
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tags: [fleeting, networks, ARPANET, packet-switching]
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created: Tuesday, October 22, 2024
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# 385af4b4_Baran_distributed_networks
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## Paul Baran's concept of a distributed network and influence on architecture of the ARPANET
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Baran worked for RAND not ARPA and his work predated the commencement of the
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ARPANET. However his model of a distributed network was highly influential on
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the design of the ARPANET and served as a consultant during the initial
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construction.
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Unlike ARPA, Baran was concerned with command and control and how a
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communication network could be resiliant enough to withstand nuclear conflict.
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He analysed the weaknesses in AT&T's telephone network and proposed a more
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robust and resiliant network model.
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If we think of the nodes of the phone network as being loci for the transferral
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of data, the phone network was highly centralised. The message would go from its
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transmitter to a central switch which would route it to the intended receiver:
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The problem is obvious: if the central switch went down, all data transferance
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stop.
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In fact this is an over-simplification. The phone network at the time was
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actually decentralised:
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This system is an improvement because each region has a switch and not all nodes
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are dependent on the central switch at all times. If the central switch goes
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down, the peripheral switches can still manage connections within their regions.
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It just means that trans-regional messages are not longer possible. Conversely,
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if one regional switch goes down, the other regions are not affected and can
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communicate between themselves and each other. So there is greater resiliance
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but still points of failure - at the central and regional switches.
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Baran conceived a _distributed_ network as his model for the most resiliant
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communications network. Instead of centralised or decentralised switches, nodes
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would connect to eachother in aggregate:
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Under this system, every node can eventually access every other node through
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intermediary nodes, without going through a main switch that establishes the
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connection.
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This is far more resiliant than the previous two network types because if a
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single node or multiple nodes go down, the message can be re-routed through
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others.
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Furthermore, by distributing the connections between nodes, the overall transfer
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of data can be more efficient as there isn't a bottleneck of centralised
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switches that can block up at times of high network activity. If one pathway is
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blocked, another route can be taken.
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The distributed model also opens up the opportunity to optimise transmission.
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For a given node in the network, it becomes possible to find the shortest route
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to another node. This would be very important in designing the IMP nodes of the
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ARPANET.
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