[ih] Significant milestones in the history of TCP/IP

[Vint Cerf]

for all practical purposes, the operation of the IMPs had little to do with
the design of TCP except for the fact that TCP did not assume one message
at a time regime that was part of the 1822 IMP/Host interface specification.

v


On Thu, Sep 17, 2015 at 6:35 PM, Bradley Fidler <fidler at ucla.edu> wrote:

> Are there other historical questions that might be answered using the IMP
> Guys' article (http://walden-family.com/bbn/imp-code.pdf) and method as a
> starting-point?  Maybe with an expanded version of the IMP program
> simulation, if someone were interested?
>
> For example, if we knew less about the IMP software -- if what Dave wrote
> below wasn't widely known -- then the simulation might have been a great
> way to test the impact of line speeds and thus how different ideas
> contributed to the initial design.
>
> As another example, consider the impact of congestion on the routing
> algorithm.  The improvements to the algorithm over time are documented in
> BBN reports, and in part through this documentation we also know that some
> of these problems were discovered as a consequence of increasing traffic
> and (if I recall correctly) node count.  It would be great to be able to
> model the response of given versions of the routing algorithm to increased
> traffic and network size.  It would require a lot of assumptions, to be
> sure, but there is a bit published on the distribution of hop counts,
> packet size, etc. of which someone could make use.  More speculatively, I
> also wonder if there's enough complaining about congestion on extant
> listserv archives from the 1980s to combine it with network maps in order
> to generate some findings on how much traffic might have been common at the
> time -- and then some even more speculative (but better than nothing!)
> findings on user counts based on estimates of traffic per user.  Perhaps we
> already have good congestion figures in the NIC archive at CHM, though, or
> somewhere else...  In any case, this is just one off-the-cuff example.  Can
> anyone think of others?
>
> This isn't to fetishize the ARPANET, but to point out one possible way to
> learn more about the interplay of these or other factors in the histories
> of networking.  One advantage of modeling ARPANET things is that the
> findings could apply in part to the many networks that were largely ARPANET
> clones.
>
> Brad
>
>
>
> On 17 September 2015 at 14:23, <dave.walden.family at gmail.com> wrote:
>
>> As Bob Armstrong knows, the IMP code (from 1973 or there abouts) that Bob
>> simulated was highly tuned for the actual line speeds of the net.  Maybe
>> the code knew about something less than 56KBS (I'd have to study the
>> listing).  Also the IMP knew of a maximum of 5 inter-IMP modem interfaces,
>> and I don't think it ever used more than 4 and I think option for the 5th
>> doesn't work (at least in the simulated version, and likely in the real
>> code).  Thus simulating lots of low speed lines might require modifying the
>> IMP assembly code.
>>
>> Sent from my iPad
>>
>> On Sep 17, 2015, at 4:14 PM, Jacob Goense <dugo at xs4all.nl> wrote:
>>
>> > On 2015-09-17 19:11, jnc at mercury.lcs.mit.edu wrote:
>> >> I suspect the only way to say with any certainty how well a network
>> >> built out
>> >> of lots of slow lines, as opposed to a few fast ones, would have worked
>> >> is a
>> >> comprehensive simulation. Which is not likely to happen, of course! ;-)
>> >
>> > Well, there is an ARPAnet IMP in simh now. According to Bob Armstrong..
>> >
>> > "The hooks are in there to allow simh to support the IMP side of the
>> > 1822 host interface, and the next step would be to recover the OS for
>> > an ARPAnet era host and then extend the corresponding simulator to talk
>> > to the IMP simulation."
>> >
>> >
>> >
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