17 Jul
2025
17 Jul
'25
5:57 p.m.
On Jul 17, 2025, at 10:45 AM, Johnny Billquist
<bqt(a)softjar.se> wrote:
On 2025-07-17 16:05, Paul Koning wrote:
First of all - no. I don't have any specs. But yes, there are RFCs that do mention
carrying DECnet over IP. I don't remember any details now, but I think they might not
even actually be using TCP in those, but my memory is very hazy. But I do have a gut
feeling that it's not the same thing that Multinet does. Remember, not only are we
talking about how the encapsulation is done, but then the fact that we're really
trying to look like DDCMP in there, so we have the specifics of DECnet over a DDCMP link,
which is all the different types of packets for init, and negotiations, and so on.
While it of course is possible that DEC did that, it would seem that it would make more
sense to do something more "clever". And OSI specifications did also touch upon
this encapsulation over IP which is more OSI generic. And DECnet phase V is that, so it
seems more likely that they went down that crazy route.
I skimmed those RFCs. It is something entirely different from what we're talking
about. What it does is map the DECnet session control interface (the program API) onto
TCP connections. More precisely, which is where the Phase V tie-in shows up, it's a
mapping of the OSI transport layer, for TP0 in particular, onto TCP. That makes some
sense: TP0 is designed to sit on top of a connection-oriented network layer (like X.25).
So essentially what this does is abuse TCP as if it were X.25.
This isn't anything like the Multinet thing because it sits a few layers higher.
There is no DECnet network layer (routing layer) involved at all. This feature only works
between two nodes both of which use the feature, and the connectivity between them is a
TCP/IP network, not a DECnet network.
It would certainly be possible for other systems that support TCP to do this; for example,
RSX could do it with your TCP support. If so, you'd be communicating over the
Internet directly, not over HECnet.
paul
On Jul
17, 2025, at 9:39 AM, Paul Koning <paulkoning(a)comcast.net> wrote:
I found it
in the VMS manuals, and they point to some RFCs. I'll read those. On Jul 16, 2025, at 6:42 PM, Johnny Billquist
<bqt(a)softjar.se> wrote:
...
It's not about the compatibility between the implementations of DECnet in the phases,
but about how you encapsulate the whole thing if you want to use TCP as the carrier...
Oh. I hadn't thought about two independent solutions to DECnet over TCP. Is the DEC
answer indeed different? If so, do you know where to find specs for it?