[ih] IENs

[Alexander McKenzie]

 Folks,

IENs are available to everyone these days, but back at the time they were
being written they were on a strictly-enforced limited distribution.  For
example, a DARPA official told one PI at BBN that his contract would be
cancelled if the IEN's he received leaked into the possession of another PI
at BBN. Therefore it is not surprising that IEN's were rarely referenced by
other documents.

Cheers,
Alex

On Monday, April 14, 2025 at 07:22:39 PM EDT, Greg Skinner via
Internet-history <internet-history at elists.isoc.org> wrote:


On Apr 12, 2025, at 11:33 AM, Jack Haverty via Internet-history <
internet-history at elists.isoc.org> wrote:
>
> The 1980s era of The Internet was explicitly a time of research and the
"Internet Experiment".    We tried to reflect that in the documents of the
day, such as RFC793.
>
> The general principle was that the "on the wire" formats and meanings
were standardized, so that any implementation of TCP could communicate with
any other implementation.  Everything else was at best Recommendations.
>
> However, there were a lot of unanswered questions, such as the best way
to deal with network errors such as dropped, duplicated, or mangled
datagrams - such as discussed in IEN69.
>
> To enable research into different techniques, the specific algorithms for
TCP functions such as retransmission timers and strategies were explicitly
*not* standardized.    That encouraged experimentation with different kinds
of network environments and different ideas about how to cope with errors.
It also permitted implementations of TCP with different goals.  An
implementer might pursue algorithms which minimized the load on their
computer system.  Or load on the network.  Or rapidity of implementation.
Or suitability for the specific user environment involved.  Or ...
>
> No one in 1981 had any significant experience with real-world TCP
networks and their behavior under heavy loads.  The ARPANET was the basic
wide-area network in use as the substrate for The Internet, and the ARPANET
provided only a reliable byte-stream service that made greatly simplified
TCP's task.
>
> IEN 177 says that the RSRE algorithm is the "current best procedure" and
"will be included in the next ... specification".  I remember talking with
Jon and others about this.  My recollection is that such an algorithm might
be included as a "best practice" recommendation, not as a mandatory part of
the standard.  In 1981 we simply didn't know enough to nail down an
algorithm and there were lots of other outstanding unresolved issues that
might be related (such as Type Of Service, Policy Routing, etc.).
>
> In 1981, The Internet was still very much an Experiment, but being pulled
forward by its adoption as a DoD Standard, and later to be rocketed forward
by its adoption in non-military networking.  I think many of those research
questions were never answered.  I recall we even at one point we even
opined that The Internet would be fine as long as we kept enough capacity
in the circuits and switches to avoid overloads, while the research
continued, seeking the "right" answers.
>
> Jack Haverty

OK, that seems reasonable.  I did a little more digging, and found that IEN
50 provides some “glue” by comparing some retransmission algorithms, using
simulations and analytical techniques to arrive at some conclusions. [1]
It seems unfortunate to me that some of these IENs couldn’t have been
included as references in RFC 793.  But as far as supporting (higher packet
loss) military networking went, some of these concerns (in theory) could
have been addressed in MIL-STD-1778 [2].  Does anyone know why they
weren’t? The US DoD sent people to those Internet Meetings from the late
1970s and early 1980s, so (in theory) they had enough information to
incorporate any additional requirements into the military standard for TCP.

--gregbo

[1] https://www.rfc-editor.org/ien/scanned/ien50.pdf
[2] http://everyspec.com/MIL-STD/MIL-STD-1700-1799/MIL-STD-1778_6676/

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