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

Bradley Fidler fidler at ucla.edu
Thu Sep 17 15:35:34 PDT 2015


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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