21 Nov
2022
21 Nov
'22
7:26 p.m.
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.
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.
paul