19 Nov
2021
19 Nov
'21
11:58 a.m.
Folks,
It might be worth looking at how Hercules encapsulates SDLC as that will do
sync mode.
There are also RFCs for these processes e.g. RFC4349.
Could we use any of these?
Dave
-----Original Message-----
From: owner-hecnet at Update.UU.SE <owner-hecnet at Update.UU.SE> On
Behalf Of Paul Koning
Sent: 19 November 2021 00:51
To: hecnet at Update.UU.SE
Subject: Re: [HECnet] ANF10 network --> DN200 (RJE, Decnet) --> should be
Ddcmp --Re3
Correction...
Character mode sync in SIMH seems utterly trivial; just treat it as an
async
stream except that the device would supply sync bytes
when the software
isn't feeding it data for a while. Perhaps just a couple, just enough to
act
as a
boundary; no need to flood the connection with data.
HDLC mode is different; HDLC is inescapably a packet mode service since
the
flags are packet delimiters. A small complication is
that it can carry
any bit
count, not just whole bytes. So the network encoding
of a simulated HDLC
device needs to handle that. A UDP encoding could just be a packet
containing the data bytes, with one byte appended to specify how many bits
in the last data byte are meaningful. (So a typical whole-byte packet
might
be "abcdefgh\010".) A TCP encoding could
be similar with a packet length
at
the start. If it's desirable not to buffer whole
frames, the stream could
be
broken into fragments with the last one (where the
flag appears) marked as
last. That would be necessary if arbitrary length frames are wanted,
though a
sensible protocol doesn't use frames longer than a
thousand bytes or so
since the 16-bit CRC isn't strong enough for really long frames.
paul
device,
On Nov 18, 2021, at 7:12 PM, Paul Koning
<paulkoning at comcast.net>
wrote:
>
> It seems like a very simple matter to simulate it as a basic character
separate from the KMC pairing. The only real question
is how you
represent
a sync data stream in a simullated device. Is it just
the byte stream
over a
TCP connection? That would be easy for synchronous
character mode. If
you also want to simulate HDLC sync devices, that's a different matter
entirely; there isn't an obvious way to do that.
In other words, if someone wants this, just design how it communicates
and do the
code, it doesn't sound hard.
paul
> On Nov 18, 2021, at 6:35 PM, R. Voorhorst
<R.Voorhorst at swabhawat.com>
wrote:
>
> No, the Dup is only simulated as Kdp/Dup combo, hence the Ddcmp
characteristics of the pair.
>
>
> Reindert
>
> -----Original Message-----
> From: owner-hecnet at Update.UU.SE [mailto:owner-
hecnet at Update.UU.SE] On
Behalf Of Johnny Billquist
> Sent: Friday, 19 November, 2021 00:31
> To: hecnet at Update.UU.SE
> Subject: Re: [HECnet] ANF10 network --> DN200 (RJE, Decnet) --> should
be Ddcmp --Re2
>
> Fair enough.
>
> But DUP11 is a sync character based interface. So that one too requires
that
you do DDCMP in software. But I didn't think simh simulated a DUP11?
>>
>> Johnny