[HECnet] Cisco DECnet routers and NML

[Paul Koning]

> On May 5, 2020, at 2:18 PM, Johnny Billquist <bqt at softjar.se> wrote:
> 
> Hi. More stuff to comment on. Fun!
> 
> On 2020-05-05 04:13, Thomas DeBellis wrote:
>> Let me clarify this a bit.  Leaving LAT aside, Tops-10 and Tops-20 implement two remote terminal protocols for DECnet.  The Digital common one is CTERM, which runs on all (or most) platforms.  Unfortunately, there are some minor problems with the current Tops-20 CTERM implementation that are annoying.  For example, you can't use space as an un-pause character, which I've been doing since about 1978.  Fixing it (if possible) means I've got to wade into the monitor and that could mean months before I come back up for air.
> 
> Right. And RSTS/E had its own protocol, as did RSX. And they were all sortof optimal for each system.
> The VMS came with CTERM, and everyone was expected to do that one, and it's more akin to an RPC-based system than some kind of terminal.

VMS had a pre-CTERM protocol, similar in style to RSX (in other words, roughly an RPC version of $QIO) but with VMS QIO semantics instead of RSX ones.  RSTS supports that one.

The original concept of CTERM is that it's a two layer system, which is why there are two specs.  The foundation layer provides the common machinery, then CTERM (command terminal) is an operating mode for carrying command line style terminal interaction.  The idea was that other modes would be created for screen editing (EDT style) and forms (like what FMS-11 supports).  I don't think that ever happened, so we're left with a very heavy protocol to do only a piece of what was originally contemplated.

At one point DEC built a PDP-11 based terminal server that speaks CTERM.  It worked, after a fashion, but it was so large, expensive, and slow, that Bruce Mann decided to see how quickly he could do better.  That's how LAT came into existence.  The resulting turf war was quite spectacular.

> But, ugly as it is, it's the closest to some kind of lingua franca. But I think CTERM have issues on every system except VMS (I don't know, they might have problems even with VMS only, who knows? CTERM is ugly.)

I suppose, though quite possibly the old VMS-specific NRT would have worked just as well as a lingua franca.  That wasn't done because the goal was to do something much bigger.

It's a bit like the long data packet headers in DECnet Phase IV -- there is lots of cruft in there that anticipates a whole lot of features that were never created, or even specified.

> But RSX ships with the system specific remote terminal clients as well, so I have a client for talking to TOPS-20 using that protocol, and a client for talking to RSTS/E using that protocol...

RSTS does a bit of connect-time magic to allow all four modes to be packaged into a single client program.  So if you install the "unsupported" version, the "set host" command just magically works no matter wich host you're dealing with, so long as it has a server installed for the old protocol.

	paul