[ih] ARPANET, operational/experimental

[Dave Walden]

At 08:56 PM 8/31/2014, Vint Cerf wrote:
>The first time I met Bob Kahn and Dave Walden was on the occasion of 
>their visit to UCLA in late 1969 or early 1970 to conduct a series 
>of experiments to generate traffic and observe the way in which the 
>IMPs and their protocols and algorithms responded. Bob Kahn had 
>concerns that under certain conditions the network would lock up and 
>this visit was a first opportunity to use the then 4-node network to 
>stress its capacity.  In the course of a couple of weeks, Bob 
>designed and I programmed a series of traffic generation and network 
>measurement experiments that indeed locked the network up multiple 
>times and in multiple ways. Reassembly lockup and store-and-forward 
>lockup stand out in my mind in particular.

Dave W.:
>In my mind the years of the ARPANET were a big experiment in whether 
>IMP hardware and sofware and host software and hardware and IMP/host 
>interfaces and host/host protocols and NWG collaboration could be 
>developed and made to work reliably enough such that the hosts could 
>talk to each other, experiments could be run (e.g., at the NMC, 
>trying packet voice, trying internetworkimg, trying improved 
>routimg, ...), and various users could try ("experiment") using the 
>net to do their more or less operational work (e.g., using a TIP to 
>access a mainframe computer rather than havin one's own, using the 
>net rather than specially leased lines to move seismic data from 
>Norway to Alexandria, ...).  And certainly some of our "operational" 
>improvements seemed like experiments ("now that we have check summed 
>the routing packets, I wonder if we will see more of those routing 
>kind of crashes").

In the case of the lock-ups mentioned by Vint, my memory is that Bob 
and I could make them happen just using the IMPs' internal traffic 
generators, and then Vint and Bob did a more systematic series of 
tests. And then much study, a simulation, and a report done back at 
BBN eventually led to the IMP code changes that were implemented.  See
  http://xn--brwolff-5wa.de/bbn-arpanet-reports-collection/BBN%20(1971)%20A%20Study%20of%20the%20Arpa%20Network%20Design%20and%20Performance%20(Report%202161).pdf
In the meantime while the change was being developed, we asked the 
hosts to please try to avoid generating traffic of the kind now known 
to lock up the net, and they did avoid it and the net continued to be 
used "operationally" for its other work and experiments.

We all had our roles in this big experiment.  A significant part of 
the BBN "IMP guys" role was to "keep it running" while continuing to 
improve it and making changes to facilitate the experiments other 
groups were doing.  I think the experiment of building the ARPANET 
and improving it for a number of years was a success.

Dave (W.)

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