14 Dec
2015
14 Dec
'15
3:07 p.m.
I think this topic was up once before, but I can't find it right now, so
I figured I'd ask.
Do anyone have some idea/documentation on how the Multinet capsulates
DECnet traffic over IP. I seem to remember it pretended it was like
ethernet, but I'd like to have all the details.
The reason is that since my TCP/IP for RSX is now at a stage where the
basic functionality is pretty stable and good, I might try something
new. Implementing a line that uses IP for transport would be useful, and
it would also be useful if it was compatible with the Multinet
implementation. I wouldn't mind also doing something compatible with
Cisco. Anyone have the details of that one?
I could also do a very RSX specific implementation, but that would be
less useful, I think.
Anyone else feel like hacking on TCP/IP on PDP-11s? I have lots of
things that could be nice to have under RSX... ;-)
Johnny
14 Dec
14 Dec
4:44 p.m.
If you can't find any docs, I might have time to packet capture today.
Sent from my iPhone
On Dec 14, 2015, at 06:07, Johnny Billquist <bqt at
softjar.se> wrote:
I think this topic was up once before, but I can't find it right now, so I figured
I'd ask.
Do anyone have some idea/documentation on how the Multinet capsulates DECnet traffic over
IP. I seem to remember it pretended it was like ethernet, but I'd like to have all the
details.
The reason is that since my TCP/IP for RSX is now at a stage where the basic
functionality is pretty stable and good, I might try something new. Implementing a line
that uses IP for transport would be useful, and it would also be useful if it was
compatible with the Multinet implementation. I wouldn't mind also doing something
compatible with Cisco. Anyone have the details of that one?
I could also do a very RSX specific implementation, but that would be less useful, I
think.
Anyone else feel like hacking on TCP/IP on PDP-11s? I have lots of things that could be
nice to have under RSX... ;-)
Johnny
5:17 p.m.
On Dec 14, 2015, at 10:44 AM, Cory Smelosky <b4 at
gewt.net> wrote:
If you can't find any docs, I might have time to packet capture today.
I went through this a while ago. I thought I posted the answer to this list at that
time.
In any case, here is the summary (from pydecnet/decnet/multinet.py which you can use as a
reference if desired).
See multinet.c
in the DECnet/Linux "dnprogs" source code for an earlier implementation
that reasonably well describes how it works..
In a nutshell: this uses UDP datagrams or a TCP connection. For
the UDP case, data packets are sent as UDP datagrams, preceded by
a four byte header consisting of a two byte sequence number
(little endian) plus two bytes of zero. It's not clear that
header is used by the receiver; it isn't in the Linux code. The
data then follows that header with no other processing. For TCP,
there is also a four byte header, but in this case the first
two-byte field is the payload length (the amount of data after the
4 byte header, little endian).
Also: the payload is the Point to Point packet payload, NOT the Ethernet format packet.
That is key, and it explains why Multinet works so poorly if either end restarts, since
the datalink requirements of the DECnet routing layer are massively violated by the
Multinet approach.
paul
6:55 p.m.
On 2015-12-14 17:17, Paul_Koning at Dell.com wrote:
I'm almost sure you did, Paul. I remember talking about this at some
time in the past, and sortof remember there being a description sent as
well, I just couldn't find it when I was searching now. So thanks for
the repeating of the information. And sorry that you'd have to repeat
it. Now I'm off to see if I can implement it.
Johnny
On Dec 14, 2015, at 10:44 AM, Cory Smelosky
<b4 at gewt.net> wrote:
If you can't find any docs, I might have time to packet capture today.
I went through this a while ago. I thought I posted the answer to this list at that
time. 
7:05 p.m.
On 2015-12-14 18:59, Robert Armstrong wrote:
Thanks. That will definitely be helpful. I'll ping you when I have
something to start testing...
Johnny
Now I'm
off to see if I can implement it.
If you get it implemented, let me know. I'll volunteer to serve as the
other end of a test link.
7:19 p.m.
On 2015-12-14 19:05, Johnny Billquist wrote:
On 2015-12-14 18:59, Robert Armstrong wrote:
Thanks. That will definitely be helpful. I'll ping you when I have
something to start testing...
By the way - seeking some inspiration... How do Multinet manage the
lines? How do you specify the other endpoint of a line?
Johnny
Now
I'm off to see if I can implement it.
If you get it implemented, let me know. I'll volunteer to serve as
the
other end of a test link.
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6 comments
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participants (4)
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b4＠gewt.net -
bob＠jfcl.com -
bqt＠softjar.se -
Paul_Koning＠Dell.com