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

Vint Cerf vint at google.com
Thu Sep 17 15:57:41 PDT 2015


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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>
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