[HECnet] DECnet/Python

[Thomas DeBellis]

I had been wanting to put some DDCMP code back into later versions of 
Tops-20.  I don't believe it exists in 5, 6 or 7.  I'm not sure if it 
made it into MRC's version of 5 for the KS and those sources have yet to 
be recovered.

A KL class machine communicates with DECnet via the CI, the NI or a DTE, 
which is a connection to a DN20.  A DN20 is a PDP-11 running DECnet (I 
think it's MCB), but I believe you are limited to Phase III.  The last 
time I was in that particular neck of the monitor woods, I believe I saw 
that the Phase IV router code would not use a DN20 as a router.  I'm 
pretty sure it would hand packets to to any node that the DN20 knew about.

It didn't look like it would be a big deal to remove that restriction to 
the DN20, but my recollection was that they never spoke full Phase IV.  
So I would need something simulating a 'smart' DN20.  Maybe a brilliant 
DN20.

Or I could make the KMC/DUP look like a MASSBUS device, adapt the 4.2 
UNIBUS based drivers to use that hardware paradigm and then simulate the 
hardware and then graft the 4.2 DDCMP code to be another transport 
option for the router.

For some very strange reason, this is my idea of fun.

On 10/27/21 12:10 PM, Paul Koning wrote:
>
>> On Oct 27, 2021, at 11:08 AM, Robert Armstrong <bob at jfcl.com> wrote:
>>
>>> DDCMP over TCP or UDP is possible with PyDECnet ...
>>   DDCMP is possible directly in simh for at least PDP-11, KS10 and VAX, depending on the support of the OS for the emulated hardware.
> For SIMH there are two approaches to DDCMP: one is the use of a DDCMP engine that's emulated, which in SIMH means DMC/DMR, DMP/DMV, or KMC-DUP pair.  Those are available in PDP-11, PDP-10 (KS10) and VAX.
>
> The other option is DDCMP over a serial link (terminal link).  That can run over TCP just as the emulated DDCMP coprocessors do (in fact, both use the "terminal mux" facility in SIMH).  So as far as the other end is concerned, these two choices are interchangeable and PyDECnet should talk to either.  To pick one example, DECnet-8 doesn't support coprocessors, but it works over serial lines; if you run that, assuming you can bring it up to Phase II, PyDECnet should talk to it.
>
> 	paul
>