21 Nov
2022
21 Nov
'22
8:41 p.m.
On 2022-11-21 19:26, Paul Koning wrote:
Yeah. NRT is a bit odd. And unless I remember wrong, some variant don't
even send anything at the start, so it's even more screwball to identify
what you should try and speak.
On Nov 21, 2022, at 1:17 PM, Thomas DeBellis
<tommytimesharing(a)gmail.com> wrote:
Interesting; I was wondering why you picked a special number? I would imagine that most
implementation wouldn't know it and maybe Ultrix-32 (OS$U32==^D18) might have been a
better choice? Ultrix-32 is of interest as its NRT is compatible with Tops-10/Tops-20 and
has the same OS type number.
NRT is a bit of a strange case because it's 4 protocols packaged inside a single
DECnet object number. So the actual protocol is identified in the first message sent by
the server. The client then must use that number to dispatch to the correct protocol
machine (or abort if it doesn't have one). The OS number in NRT, on the other hand, is just
information and should be ignored just like it should be ignored in every other protocol.
Right. Once you have some data, there is better information than the OS
identifier.
As for "special" do you mean the value 192?
The DAP spec explicitly assigns the range 192-255 for "user-specified operating
systems". So for an NFT to fail when it gets that code is a major protocol
violation. Identifying Linux as Ultrix would be misleading, they are quite different
operating systems with no common ancestry or code base.
I'm not sure I agree. While I don't mind grabbing some
undefined/reserved number for a new implementation, Linux is after all
just another Unix in this sense, and would suite very well into just
pretending to be Ultrix. Shared codebase seems rather irrelevant. It's
much more about the actual properties and behavior of the system. I
generally always group all Unix-like systems together. There are some
times when you want to differentiate between them, but for network
protocols like this, I can't think of a single reason.
In a sense, they have a very shared ancestry.
Johnny
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|| on a psychedelic trip
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