DECserver and LAT migration

[gilemon]

Hi,
I'm trying to replace a discontinued DECserver 90TL with a newer type of Terminal Server (Moxa).
The 90TL is used to interface with some serial devices like an ASCII controller from DYNATECH.

I'm having trouble getting some information online about this kind of task.
I found some Terminal Server supporting the LAT protocol like the ELS-16 II Terminal Server from Equinox or the DECServer ConX4 from Digital Networks.
But this hardware doesn't look well supported neither, and the ultimate goal would be to get rid of the LAT protocol.

I'm trying to find a general strategy, porting guideline, but I can't find much information about the LAT protocol specification.

Does anybody has ever done this before, or has any advice?

Thanks

[Steven Schweda · Accepted solution]

I still use LAT with my VMS systems (mostly
to access serial console ports on various
Cisco, HP, IBM, Sun, and other systems), and
I only recently replaced my DECserver 200/MC
with a 90TL, so I know nothing, but ...

> [...] the ultimate goal would be to get
> rid of the LAT protocol.

Why? Do you expect it to stop working?

> The 90TL is used to interface with some
> serial devices like an ASCII controller
> from DYNATECH.

Not much meat on that description. How is
the terminal server/port configured for that
device? What, exactly do you do with it?
Have you looked at reverse-Telnet (which the
90TL can do, can't it)?

> I'm trying to find a general strategy,
> porting guideline, [...]

Perhaps too much depends on the details of
what you're trying to do.


I see relatively cheap DECserver 90TL (and
related) devices pretty frequently on Ebay,
so it's not immediately obvious that the
current configuration is doomed because of a
lack of hardware. You're asking about this
in a Tru64 forum. I might worry more about
Tru64 (and the hardware on which it runs)
than I would about a DECserver 90TL and/or
LAT.

[gilemon]

Thanks a lot for the feedback.

> [...] the ultimate goal would be to get
> rid of the LAT protocol.

>> Why? Do you expect it to stop working?

We are decommissioning a backbone of Terminal Servers because we are migrating from FFDI to fast Ethernet for obsolescence management matters.

> The 90TL is used to interface with some
> serial devices like an ASCII controller
> from DYNATECH.

>> Not much meat on that description. How is
>> the terminal server/port configured for that
>> device? What, exactly do you do with it?
>> Have you looked at reverse-Telnet (which the
>> 90TL can do, can't it)?

The 90TL configuration:

Access remote
Type hard
Input Output speed 4800
Default protocol LAT
character size 8
stop bit dynamic
parity none
session limit 1
Signal control disable
autoprompt disable
autobaud disable

The ASCII controller is a serial switch used to communicate with some serial equipments.

Yes, we do use reverse-Telnet.

> I'm trying to find a general strategy,
> porting guideline, [...]

>> Perhaps too much depends on the details of
>> what you're trying to do.

Indeed, as stated above, this issue is embedded into a FDDI migration.
So it looks like the first step would be to find a way to use the 90TL in standalone mode in order to extract it from the TS backbone, then find a solution for the LAT by considering the details of the equipements we want to upgrade.

>> I see relatively cheap DECserver 90TL (and
>> related) devices pretty frequently on Ebay,
>> so it's not immediately obvious that the
>> current configuration is doomed because of a
>> lack of hardware. You're asking about this
>> in a Tru64 forum. I might worry more about
>> Tru64 (and the hardware on which it runs)
>> than I would about a DECserver 90TL and/or
>> LAT.

Thatâ s true. Itâ s another issue we will have to address.

[Steven Schweda]

> We are decommissioning a backbone of
> Terminal Servers because we are migrating
> from FFDI to fast Ethernet [...]

I've never seen one of those multi-module
backplane gizmos in person. I've always
assumed that they had an Ethernet uplink, but
I can believe that there was an optical fiber
option, too.

> [...] find a way to use the 90TL in
> standalone mode in order to extract it from
> the TS backbone, [...]

If your 90TL looks like mine, then it wants a
10Base2 (Thinwire) Ethernet connection, so it
can't really do _fast_ Ethernet. Mine is
connected to the BNC port (next to the unused
AUI port) on an old (but versatile) hub. (I
still have some old VAX systems with Thinwire
connections, too, and a nice collection of
genuine DEC Thinwire cables, T's, and
terminators. You can't have too much junk, I
always say.) One (10BaseT) port on that
(old, slow) hub is connected to one
(10/100BaseT) port on a newer switch (along
with most of my other stuff).

I haven't tried to find any
10Base2-compatible hub, switch, transceiver,
or whatever hardware in recent years, so I
can't suggest much on that side.

According to its label, my 90TL wants
"5.1Vdc" at "1.8A". I power mine from a
(junk store) 5V, 2A wall-wart with a
home-modified cord. An 8-pin connector for
an old Mac or Sun serial port fits well (even
though it has a pin where it should have a
locating key). The male connector on the
power supply is wired like this:

-_-
+----o o o----+
(+)---+---o [ ] o---+---(-)
+-----o o-----+

(Copy+paste into a fixed-width font, or use
your imagination.)

A typical serial cable may not have all six
desired wires, but I'd expect at least two on
each side, which should be plenty. If I had
a working unit in a backplane, I'd use a
voltmeter to see what's where on that
mini-DIN power hole, rather than trusting me,
but you're free to believe anything.

The pins on an old PS/2 mouse cable connector
(with its plastic key broken off) don't align
very well with the 90TL holes, so I'd advise
against trying to use one of those. (That's
the voice of experience speaking.)

Or, you could try to find an official DEC
power supply. (I didn't try.) Or an actual
7-pin mini-DIN connector. (The local junk
store had a cheap Mac modem cable, so my
choice was easy.)

With my VMS stuff and small network, I still
use MOP for the DECserver software downloads,
but I assume that bootp works, too. LAT is
not routable, so you need to worry about
keeping things on a single network segment,
at least until you can switch over to
(reverse-) Telnet. If your application
software just talks to a LAT device which is
mapped to a DECserver port, then, knowing
nothing, I'd guess that it might be fairly
easy to have it do the same stuff with a
Telnet device. If you do fancy hardware
control stuff with LAT, then converting to
Telnet might be harder.