using Vax as fileserver for Xerox Lisp Machine [the facts!]

[Jeff Mogul]

Since I don't read Unix-wizards, I didn't realize that this had turned
into a hot issue; thanks to some other Stanford people for alerting me.

I wrote a lot of the "Stanford Unix Pup" software that Xerox has been
distributing.  We expect to distribute this as "user-contributed" (i.e.,
totally unsupported) software in 4.3BSD.  The CMU/Stanford "packet-filter"
device driver will also be in 4.3BSD, probably as part of the official
kernel.  Please do not ask me (or anyone else from Stanford) for copies
of this code; you won't get it from me.

Pup is an obsolete protocol, but in much the same way that FORTRAN is
an obsolete language ... people still use it.  The Stanford Pup system
includes Telnet, FTP, Leaf (remote file random access from your Xerox Lisp
Machine) and other Pup services (name lookup, gateway-on-a-Vax, etc.)
We support both 3Mb and 10Mb ethernets, but no other data link layers.
This has been running for several years without any changes, so it
is fairly solid.  Anyway, we don't intend to do any further work on it.

The "Pup" code in the 4.2BSD kernel is bogus; we don't use it at all
and I hope it won't be in 4.3BSD.  All our code runs in user-mode
programs, except for the packet-filter driver (which is not specific
to Pup.)

I should clear up some misinformation: Pup cannot deal with >255 hosts
on a single cable; but Pup is an internetwork protocol (one of the first:
see Boggs, Schoch, Taft, and Metcalfe "Pup: an Internetwork Architecture"
in IEEE Trans. on Comm., April 1980) so you can have up to 254*255 hosts.
Xerox has far more than 255 Pup hosts; I think they have about 125 Pup
subnets and thousands of hosts.  Stanford has 36 subnets and almost 600
entries in our Pup host table (although 95% of those hosts no longer rely
on Pup.)