[ih] early networking

[Steve Crocker]

John,

My understanding re the idea for the IMPs is slightly different.  Yes,
there was pushback from some of the sites, but I have understood the
introduction of the IMP idea came from Wes Clark.  (See
https://en.wikipedia.org/wiki/Wesley_A._Clark)  He was deeply involved with
small computers.  The introduction of  the IMPs into the design provided a
clean separation between the subnet and the hosts.  The reliability of
the overall system was dependent only on the IMPs and the lines.  In those
days, it was fairly rare for an operating system to have 24 hours of
continuous operation.

Re the protocol, the few of us who were involved at the outset of the host
level protocol design focused on connections as the basic building block.
I'll take the blame for this narrow focus if we need someone to blame.  (On
the other hand, if it's a matter of giving credit, there were several of
us.)  Walden's IPC concept came along after we were far down the path of
designing the host-host protocol.  That said, general interprocess
communication was part of our thinking from the start.

John White from UCSB also pushed for remote procedure calls as a basic
building block.  It was a powerful idea but didn't dissuade us from
choosing a virtual bitstream as the building block.  Maybe it should have.

Along a separate path, Danny Cohen was interested in real-time
applications, particularly voice and flight simulation.  His work, among
others, led to using messages that were not subject to flow control.

In all cases, the notion of layers was fundamental and an intrinsic part of
everyone's thinking coming out of the August 1968 meeting.

Steve


On Mon, Apr 29, 2024 at 3:58 PM John Day via Internet-history <
internet-history at elists.isoc.org> wrote:

>
> As we all know, the ARPANET was the first major packet switching network.
> It was built to be a production network to lower the cost of computing for
> ARPA Projects.  Cyclades was built to be a network to do research on
> networks. Cyclades was a platform, what today would be called a clean-slate
> approach having seen the ARPANET. (There was considerable interaction
> between BBN and CYCLADES: As Dave Walden (who led IMP team) told me, so
> ’they wouldn’t make the same mistakes we did.’ ;-) And Jean-Louis Grangé
> (led the CIGALE team) spent a fair amount of time at BBN.)
>
> Because Roberts had gotten considerable resistance from the potential host
> sites when he proposed just a network of hosts, the IMPs were proposed to
> ‘off-load’ the network from the hosts. Hence for the ARPANET, the host used
> the IMP-Host protocol to allocate a ‘connection’ to the destination and
> then the Host-Host Protocol created a connection between processes in the
> two machines. The applications were built on top of it. (Note NCP did flow
> control but no retransmissions because the IMP subnet was reliable.) This
> is when layers were first introduced. (Again, Walden confirmed for me that
> there were no layer diagrams of the IMP subnet and I wouldn’t have expected
> them then.) This is when the idea that networking was IPC began. Walden
> wrote a very early RFC proposing IPC for a resource sharing network.)
>
> sender