[ih] Nit-picking an origin story

[John Day]

But different queue lengths?

> On Aug 19, 2025, at 17:17, vinton cerf via Internet-history <internet-history at elists.isoc.org> wrote:
> 
> Even back in the 1970-1972 period, some of my experiments with Bob Kahn
> showed that the ARPANET IMPs were capable of adaptive alternate routing so
> that I was able to inject about 80 kb/s of traffic from UCLA destined for
> SRI that switched between a direct route and an indirect one through Santa
> Barbara even though the direct and indirect paths had at most 50 kb/s each.
> 
> v
> 
> 
> On Tue, Aug 19, 2025 at 4:50 PM Jack Haverty via Internet-history <
> internet-history at elists.isoc.org> wrote:
> 
>> On 8/18/25 07:00, John Day via Internet-history wrote:
>>> This last one I think doesn’t get enough credit. It is a very small
>> thing, but I think was a major contribution to the success of the ARPANET.
>> It would have worked at 2.4 or 9.6, but been so glacially slow as to have
>> been considered not successful. At 50Kbps, we could do real work that was
>> way beyond what people expected. Not to take anything away from the great
>> software development that went into the IMPs and the NCPs, etc. I really
>> think this gets too little credit for the success.
>> Performance was also an issue as the ARPANET grew and traffic
>> increased.  One of the limiting factors to performance was the routing
>> algorithm.   Packets were always sent on the "shortest" path.   But that
>> meant that the aggregate performance was also limited to 56kb/sec, which
>> was the maximum line speed of any path. Even after there were multiple
>> possible routes across the US, routing would typically only utilize one
>> path, whichever was shortest at the time.
>> 
>> There was a lot of analysis, simulation, and testing done over the 80s
>> as the IMP's internal algorithms were improved.  One ot the targets was
>> "multipath routing", which meant figuring out a way to use more than
>> just the shortest path between two IMPs and their attached host
>> computers.  That would enable hosts to get more than 56KB/sec throughput
>> across the 'net, as well as improve the overall efficiency of use of the
>> expensive longhaul circuits.
>> 
>> Such issues were also present in the Internet of course.  A similar
>> desire existed to be able to use more than one path through the
>> Internet.  The ICCB's "To Do List" contained items such as "Multipath
>> Routing" and "Expressway Routing" in the early 1980s. But there couldn't
>> be much progress on that since the Internet routing, at that time,
>> didn't have any real notion of "shortest path", but used the simple
>> metric of "hop counts" as an interim metric for decisions on datagram
>> routes.
>> 
>> Most people likely haven't seen much info about the internal algorithms
>> used inside the ARPANET, which were captured in reports to the
>> government sponsors but not so much in RFCs et al.
>> 
>> There's some large reports on the "ARPANET Routing Improvements" work
>> done circa 1980.  One of the reports is online in PDF form at
>> https://apps.dtic.mil/sti/html/tr/ADA121350/index.html  Others are
>> probably online in DTIC as well, for any historians interested in the
>> inner workings of the ARPANET and how it evolved over its lifetime.
>> 
>> Jack Haverty
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