Discussion:
DECnet-Plus over IP on an emulated VAX?
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Steven Schweda
2017-03-28 00:35:56 UTC
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For a while, I've been fooling around occasionally with a
SIMH emulated VAX (VMS V7.3) on a Mac Pro ((Early 2008), OS X
10.11.6), and being annoyed by the need to use FTP to move
files to and from my main VMS (Alpha) system. It took me
long enough to figure out how to get the Mac to route IP
traffic between the SIMH/tap0-interface subnet to the real
(Mac-Alpha-others) LAN that I lacked sufficient ambition to
investigate trying to run DECnet-over-IP to obviate the usual
IP-only methods. Until today.

Who knew how easy this is, and why didn't I?

WISP $ dire/date/prot alp-l::login.com;

Directory ALP-L::SYS$SYSROOT:[SYSMGR]

LOGIN.COM;128 1-JAN-2017 22:06:40.49 (RWED,RWED,RE,RE)


ALP $ dire/date/prot wisp.antinode.info::login.com;

Directory WISP.ANTINODE.INFO::SYS$SYSROOT:[SYSMGR]

LOGIN.COM;127 1-JAN-2014 00:58:52.43 (RWED,RWED,RE,RE)


Aside from a little fooling around with the proxies, and
having to tell NET$CONFIGURE.COM to use "Domain" as well as
"Local" for "directory services", this stuff seems to work
with much less fuss than I expected. (Assuming, of course,
that you already have DECnet-Plus installed and (minimally)
configured.)

Does everyone with an emulator already know all this
stuff? Having read nothing about it, I always assumed that
some serious effort was required to enable the DECnet-over-IP
transport, but it seems that (assuming you enabled PWIP on
the TCPIP side) the actual effort would be to _disable_ the
IP transport, not to enable it.

It's no wonder that everyone here is so enthusiastic about
DECnet-Plus. It's a miracle.
Dirk Munk
2017-03-28 13:41:29 UTC
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Post by Steven Schweda
For a while, I've been fooling around occasionally with a
SIMH emulated VAX (VMS V7.3) on a Mac Pro ((Early 2008), OS X
10.11.6), and being annoyed by the need to use FTP to move
files to and from my main VMS (Alpha) system. It took me
long enough to figure out how to get the Mac to route IP
traffic between the SIMH/tap0-interface subnet to the real
(Mac-Alpha-others) LAN that I lacked sufficient ambition to
investigate trying to run DECnet-over-IP to obviate the usual
IP-only methods. Until today.
Who knew how easy this is, and why didn't I?
WISP $ dire/date/prot alp-l::login.com;
Directory ALP-L::SYS$SYSROOT:[SYSMGR]
LOGIN.COM;128 1-JAN-2017 22:06:40.49 (RWED,RWED,RE,RE)
ALP $ dire/date/prot wisp.antinode.info::login.com;
Directory WISP.ANTINODE.INFO::SYS$SYSROOT:[SYSMGR]
LOGIN.COM;127 1-JAN-2014 00:58:52.43 (RWED,RWED,RE,RE)
Aside from a little fooling around with the proxies, and
having to tell NET$CONFIGURE.COM to use "Domain" as well as
"Local" for "directory services", this stuff seems to work
with much less fuss than I expected. (Assuming, of course,
that you already have DECnet-Plus installed and (minimally)
configured.)
Does everyone with an emulator already know all this
stuff? Having read nothing about it, I always assumed that
some serious effort was required to enable the DECnet-over-IP
transport, but it seems that (assuming you enabled PWIP on
the TCPIP side) the actual effort would be to _disable_ the
IP transport, not to enable it.
It's no wonder that everyone here is so enthusiastic about
DECnet-Plus. It's a miracle.
I'm not sure what you're doing, but you only have to run net$configure
in advanced mode if I remember correctly, and use domain as choice. No
need to use Local as directory service, domain means that you will be
using IP DNS names for your DECnet over IP nodes, something like
alpha.mydomain.org, and vax.mydomain.org. Local would mean that you
would be using locally registered OSI names, and they are useless for
DECnet over IP.

And indeed using DECnet over IP is dead simple.
Steven Schweda
2017-03-29 03:21:00 UTC
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I'm not sure what you're doing, [...]
As I said, I'm running a SIMH emulated VAX (VMS V7.3) on a
Mac Pro ((Early 2008), OS X 10.11.6), and was trying to get
the same kinds of network connectivity between the emulated
VAX and the other VMS systems (real hardware) on the LAN as I
already had among all those real-hardware systems. That is,
DECnet and IP.

There's no Ethernet connector on the emulated VAX, only an
emulated DELQA with a pseudo-interface on the Mac, so, I
can't run a cable from the emulated VAX to the usual LAN
hardware. The pseudo-interface is fine for IP communication
with the Mac itself. Then, with a little effort, it's
possible to persuade the Mac to route IP between its
normal/real Ethernet interface (en0, 10.0.0.79) and the
pseudo-interface (tap0, 10.0.1.79) which shares a subnet with
the pseudo-interface (QE0, 10.0.1.32) on the emulated VAX.
(Who would have guessed that IP routing between interfaces is
disabled by default on the Mac? Not I.)

That solves the IP connectivity problem, but not the
DECnet, unless DECnet also uses IP.
[,,,] but you only have to run net$configure in advanced
mode if I remember correctly, and use domain as choice.
"Basic" mode is fancy enough for this, apparently.
[...] No need to use Local as directory service, [...]
Perhaps, but until now I had been using Local everywhere,
because I had no need for DECnet-over-IP for the
real-hardware systems, and some of the systems are old-VAX
without DECnet-Plus.
And indeed using DECnet over IP is dead simple.
It's pretty close. I enabled Domain naming on the
emulated VAX, and tried a "DNS_name::" to talk to the main
Alpha system, and was amazed to see OPCOM messages on the
Alpha complaining about the bad credentials. After that, I
added Domain naming on the Alpha, and added some DNS proxies
on both systems, and everything just worked.

There were some goofy aspects in the IP$10.00.01.32
"hostname" which the Alpha was seeing before I enabled Domain
naming there. You can define a proxy with that mess, but it
won't work without the (should-be-)insignificant zeros in the
thing. So, it's not all perfect, but it's not too bad.

I haven't paid close attention to emulator discussions
over the years, and I couldn't remember anyone discussing
DECnet access to an emulated system, hence my original
question(s).
Bob Koehler
2017-03-29 14:19:07 UTC
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Post by Steven Schweda
As I said, I'm running a SIMH emulated VAX (VMS V7.3) on a
Mac Pro ((Early 2008), OS X 10.11.6), and was trying to get
the same kinds of network connectivity between the emulated
VAX and the other VMS systems (real hardware) on the LAN as I
already had among all those real-hardware systems. That is,
DECnet and IP.
Perhaps VMScluster over IP? I've played with it at home.
John E. Malmberg
2017-03-29 23:48:22 UTC
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Post by Steven Schweda
I'm not sure what you're doing, [...]
As I said, I'm running a SIMH emulated VAX (VMS V7.3) on a
Mac Pro ((Early 2008), OS X 10.11.6), and was trying to get
the same kinds of network connectivity between the emulated
VAX and the other VMS systems (real hardware) on the LAN as I
already had among all those real-hardware systems. That is,
DECnet and IP.
There's no Ethernet connector on the emulated VAX, only an
emulated DELQA with a pseudo-interface on the Mac, so, I
can't run a cable from the emulated VAX to the usual LAN
hardware. The pseudo-interface is fine for IP communication
with the Mac itself. Then, with a little effort, it's
possible to persuade the Mac to route IP between its
normal/real Ethernet interface (en0, 10.0.0.79) and the
pseudo-interface (tap0, 10.0.1.79) which shares a subnet with
the pseudo-interface (QE0, 10.0.1.32) on the emulated VAX.
(Who would have guessed that IP routing between interfaces is
disabled by default on the Mac? Not I.)
That solves the IP connectivity problem, but not the
DECnet, unless DECnet also uses IP.
Set the MAC address for the SimH interface bridged to the public network
to match what DECNET Phase IV will set them to when it starts up.

LAT, Decnet IV, will then work as long as DECNet is started before TCP/IP.

I was running a FreeAXP / SimH cluster on a Mac for a few years that
way. I put the SimH/VAX in a Scientific Linux VM to let Virtualbox
handle the bridging.

Regards,
-John
***@qsl.net_work
Steven Schweda
2017-03-30 03:51:36 UTC
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Post by John E. Malmberg
Set the MAC address for the SimH interface bridged to the
public network to match what DECNET Phase IV will set them to
when it starts up.
With DECnet-Plus (Phase V), I don't care about the MAC
address. "bridged"?

I'll admit that I have not yet found an explanation of
SIMH networking which made much sense to me, so there are
likely many things about it which I don't understand.

I did manage to find (and install) a "tun/tap driver for
Mac OS X", which I seem to be using. On the Mac, I
configured (ifconfig) tap0 with 10.0.1.79/24 (where the
real-LAN Ethernet interface, en0, is at 10.0.0.79/24). On
the VAX, QE0 is at 10.0.1.32/24. (SIMH: "attach xq
tap:tap0", plus the usual TCPIP stuff.) This provides an IP
path to the Mac (on the (all-software) 10.0.1.x subnet), and
the Mac (with some prodding) then routes IP traffic to the
main LAN, 10.0.0.x, which includes the router to the outside
world.

I have no idea if this scheme resembles what others are
using. It works for me, for all the IP stuff (normal IP,
DECnet-Plus-over-IP). It does nothing for LAT, et al.,
because, so far as I understand it, it provides no direct
connection between the VAX and the physical LAN (10.0.0.x).
This covers all my needs, but if anyone has a clear
explanation of how to put the emulated VAX onto the real LAN,
then I'd be interested. This may be documented somewhere,
but, when I looked, I found only a bunch of mostly-old
material which seemed mostly unrelated to a Mac. If there's
a non-obsolete guide to how to configure this stuff to do
more than I already have working, then I'd be grateful for a
pointer.
Post by John E. Malmberg
[...] I put the SimH/VAX in a Scientific Linux VM to let
Virtualbox handle the bridging.
So far as I can see, bridging is what I'm not doing.

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