Date:   Thu, 04 Aug 2022 11:19:27 +0100
From:   Steven Whitehouse <swhiteho@...hat.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org, Christine caulfield <ccaulfie@...hat.com>
Subject: DECnet - end of a era!

Hi,

I've just spotted the thread about dropping DECnet support from the
kernel - apologies for being a bit slow here as somehow the initial
announcement missed me.

I think it is definitely time for this to happen. It has been broken
now for several kernel versions, and as mentioned on another thread,
there is no iproute2 support any more, so there is no way to configure
it in user space anyway.

Do people still use DECnet? Definitely! I had a request only a few
weeks ago from someone asking advice on which vintage of the code to
use. On the other hand the number of users must be very very small, and
they must all be using older kernel/distro versions since the more
recent versions are non-functional. All the users I've been aware of
were actively looking to move away from it as soon as they reasonably
could.

Nobody has stepped up to maintain the code over a long period now, so I
think it has reached the point where removal is the only sensible
option. Still, it would be shame to let that happen without mentioning
some of the applications to which we have, over the time it was
functional, that people have used it for...

 - Satellite comms (when the other end of the link is in orbit, it is
expensive to replace it!)
 - Railways (I don't know for exactly what purpose!)
 - Industrial Control
 - Remote Sensing (again the remote end of the link was very expensive
to replace/update!)
 - X-Windows
 - DECnet to IP gateways

I originally looked into starting a Linux DECnet project because my
then employer used a lot of DEC VAX machines and I thought it might
help the popularity of Linux if people had an easy migration path! I
has started working from the available docs, but there were a few gaps.
Luckily Eduardo Marcelo Serrat had also begun some work at around the
same time and was able to supply the missing pieces of that puzzle, as
we combined our efforts.

Chrissie Caulfield put in a heroic effort on the userland side
(although we all contributed bits to both kernel & userland) and we had
a working stack! I don't remember any of the timings, so I've no idea
of the three of us who started first, but we all somehow found each
other and were able to collaborate together on the project.

Of course many others have contributed over the years, and we had a lot
of support from the Linux network developers too. Many thanks to all
who've helped along the way, we very much appreciate all the assistance
that we've had. Alan Cox provided initial encouragement, with Davem and
Alexey Kuznetsov later on, and with contributions from many quarters
which were very gratefully received.

Farewell to the Linux DECnet stack :-)

Steve.

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