39 lines
1.4 KiB
Markdown
39 lines
1.4 KiB
Markdown
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---
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tags: [ARPANET, networks, computer-history]
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created: Friday, October 18, 2024
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---
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# e470bf3d_IMPs_in_the_ARPANET
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Within the #ARPANET, IMPs (Information Message Processors) were nodes
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distinguished from [hosts](Network_hosts.md). They were computers designed to
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receive and route the the packets from one host to another, described as
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"adaptive routing".
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Their job was to:
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- packetize or reassemble the data from the host
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- find the most efficient pathway from one host to another
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- store packets in their buffers whilst attending to other requests
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- retry the transmission a set number of times in the case of error or data
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corruption
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- confirm successful transmission
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These responsibilities required the IMP to "know" the location and addresses of
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other IMPs and hosts on the [network](Network_fundamentals.md) and their
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proximity to them.
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From the point of view of the host user, the existence of the IMPs would be
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hidden. Hosts would connect to eachother transparently - it would appear as if
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you were directly connecting to the other host rather than an IMP.
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Thus an IMP was a subnetwork within the broader ARPANET: the IMP would be the
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core of this subnetwork and the links to its direct hosts, the periperhy.
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Initially, in its full extent, the ARPANET comprised a network of these
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subnetworks.
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IMPs were later known as 'gateways' and were the precursors to what we today
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call routers.
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