Is ChaosNet remembered more accurately than Maryland summer parties in 1982? Let's find out!

> Usage of Chaosnet presumably waned as Lisp machines became less and less popular.

The relative drop in popularity of Lisp Machines wasn't the primary
reason for ChaosNet use to decline. Until the mid-1980s at MIT,
ChaosNet was also widely used in everyday work on UNIX, VMS, and
TOPS-20. ChaosNet was not focused on the small number of research
groups that used Lisp Machines. By the mid-1980s, most operating
system distributions included TCP/IP. There were more deployed
machines that could communicate over TCP/IP than over ChaosNet.
However, MIT did not yet have a supported IP network covering every
building (where "supported" means either centrally supported by MIT,
or supported by a major research lab, depending on the building in
question).

The remaining reasons to use ChaosNet were network services and
reliability. For example, SUPDUP arguably provided a much better
remote-login experience than TELNET, and some (or possibly all)
machines implemented SUPDUP only over ChaosNet, not over TCP. There
may have been other important ChaosNet-only services on machines such
as reagan (more commonly known as "b" -- for "bonzo") at the AI Lab.

In some locations (possibly only on Vassar Street), keeping the
ChaosNet software stack for reliability was worthwhile even though IP
was obviously the only way to directly reach the whole outside world.
Using the ChaosNet software stack, one could communicate within parts
of the main campus as well as NE43, and relaying email to the outside
world worked, at least often. That was sometimes the only networking
that a person needed to accomplish their work. In building 36 and 38,
the earliest set of IP addresses was on the 18.27/16 network. That
specific implementation of IP may have involved some type of protocol
tunneling or protocol translator. At one time, this was maintained at
the Digital Signal Processing Group (sixth floor of 36) and may have
run on a machine named yosemite-sam (or some other Looney Tunes
character). This was largely successful, but not really "supportable."
Eventually, a separate network was built in 36 and 38 using 18.62/16
IP addresses, and any machine wired to that network could not use
ChaosNet services elsewhere. Over time (more than a year), every
machine moved off of 18.27/16 and onto 18.62/16. At that point, it
rarely made any sense for anyone outside of NE43 to build or enable
ChaosNet support on any machines.

Even before this, the cost/benefit became too high for some people to
bother building, installing, or enabling ChaosNet. For example, Alan
Wu, who was the head of the Electrical Engineering and Computer
Science Educational Computing Facility (EECS ECF) made a decision in
the mid-1980s that his staff would no longer compile ChaosNet into the
kernel on their BSD machines. The reasons may have included the extra
work of a nonstandard build tree, and machine crashes within the
ChaosNet code. Similarly, syaadmins in other places saw that it didn't
make sense to devote any resources to the small benefits of ChaosNet.

On a larger scale, Project Athena BSD kernels did not include ChaosNet
code (or, if they ever did at the beginning, it was discontinued after
a while or was never commonly used). However, Athena was probably not
a major factor in the decline of ChaosNet. Athena workstations were
never connected to unsupported networks such as 18.27/16, and Athena
users typically had no SUPDUP use case. ChaosNet use was already
mostly gone (outside of NE43) before individual faculty and staff were
generally able to request Athena workstations for their offices or
labs.