[HECnet] DECnet/Python

[Keith Halewood]

We had VAXen and micro VAXen with KMV11s talking X25 to the JANET network with DEC’s PSI software. At some point we ran DECnet over PSI
 and eventually X25 1984 over Ethernet. And then UK academia saw the light and went TCP/IP - what a relief that was :)

Keith

On 28 Oct 2021, at 19:58, John Forecast <john at forecast.name> wrote:

 The PCL-11B was a CSS product which allowed up to 16 Unibus PDP-11 to be connected together over a TDM bus running at 1 megabyte/sec. I’m pretty sure it didn’t use DDCMP. I’m not sure about Phase II but for  Phase III each node was set up as a multi-point master (PCL-0.0) and the remote nodes were multi-point tributaries (PCL-0.1 to PCL-0.15) so it would appear as a fully connected mesh. At the end of Phase III, Hardware Engineering built a small number of prototype Unibus ethernet boards (maybe 10 total) so they could get some experience with ethernet (this was a programmed I/O device with 1 transmit and 1 receive buffer, sort of like some of the early 3Com devices). I used a similar technique to the PCL to get RSX-DECnet Phase III running (slowly) over ethernet.

  John.

On Oct 27, 2021, at 8:50 PM, Paul Koning <paulkoning at comcast.net<mailto:paulkoning at comcast.net>> wrote:

PCL is a parallel inter-computer link.  DECnet supports it with DDCMP; I think RSX has the ability but I don't know if anyone else does.

paul

On Oct 27, 2021, at 8:13 PM, Thomas DeBellis <tommytimesharing at gmail.com<mailto:tommytimesharing at gmail.com>> wrote:


Remind me what "PCL" transport is, please?

Tops-20 seems to have had DECnet over X.25 at some point, but I don't see any of source for that in the PANDA distribution.  It is possible that it may be on a standard DEC distribution tape on trailing-edge.

Maybe

In certain cases, DEC would not release source, even if you paid to be a source site.  So you can't get TGHA (bummer) nor the NICE process (double bummer).

On 10/27/21 9:52 AM, Paul Koning wrote:

On Oct 27, 2021, at 9:20 AM, Johnny Billquist <bqt at softjar.se><mailto:bqt at softjar.se> wrote:

To answer Brian in one way - I usually try to organize so that people get hooked up to someone physically close to them, who are sortof local HECnet access points. There are a bunch of people I have on my list that I tend to make use of for this, but it is otherwise pretty flexible.

But it don't make sense to have the link going to someone far away. That just means silly roundtrips if you then talk to someone nearby, while for connections far away, it's going to make that jump anyway, no matter where you connect.

And a few questions/comments on what Paul wrote:

On 2021-10-27 15:06, Paul Koning wrote:


A couple of considerations:
1. Is there a backbone router in your area?  If yes, you'd want to connect there.


With area I assume you mean physical area here, and not DECnet area.


Oops.  Yes.  But everywhere else I meant DECnet area, and should said so clearly.



...
For the others, Paul pretty much summed it up. In addition, it should probably be mentioned that Multinet over TCP or UDP is possible inside VMS and RSX (as well as with PyDECnet). DDCMP over TCP or UDP is possible with PyDECnet (actually, I could probably add that in RSX as well), while GRE is mainly for Cisco, but I think PyDECnet also can do that one?

So choices are somewhat dependent on what system/software you are using.


Yes, PyDECnet supports: real Ethernet, Ethernet bridging over UDP, GRE, Multinet over TCP (and UDP but don't), DDCMP over TCP, UDP, simulated async connections including Telnet, real async connections, and sync connections via my DDCMP framer device.  In other words, most of the datalinks DECnet has ever supported.  Missing are 802.5 token ring, HDLC, X.25, and PCL, I think that's about it.  Some day I'll think about 802.5 support not so much for that but because it would enable DECnet over WiFi.

        paul




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