[HECnet] Is this the most up to date version of DECnet OS numbers?

Paul Koning paulkoning at comcast.net
Mon Nov 8 07:41:18 PST 2021



> On Nov 8, 2021, at 10:33 AM, Paul Koning <paulkoning at comcast.net> wrote:
> 
> 
> 
>> On Nov 8, 2021, at 10:16 AM, Johnny Billquist <bqt at softjar.se> wrote:
>> 
>> On 2021-11-08 15:57, Paul Koning wrote:
>>>> On Nov 7, 2021, at 6:40 PM, Thomas DeBellis <tommytimesharing at gmail.com> wrote:
>>>> 
>>>> ...
>>>> On the other hand, I don't remember my FAL/NFT/DAP blowing up on the wrong system, either (they blow up on plenty of other stuff...)  It would appear that there are two (2) separate lists of system type bytes, one for NRT and the other for DAP, viz:
>>>> ...
>>> I don't know why DAP includes an OS type code at all.  When I was working on DECnet architecture I repeatedly argued that DAP implementations that do OS type checks are broken, because they are assuming that they can correctly deduce the properties of some remote system from its OS code.  The correct way -- which is supported, in detail, by DAP -- is to look at the feature flags to determine what the OS can and cannot do.  And if those flags are insufficient for a particular case, the solution is to extend the protocol to add the missing information.
>>> In other words, a client should conclude "the server can do X because it told me it supports X" and not "the server can do X because it is running OS Y".
>> 
>> Absolutely agree. And I wonder if any software really do make use of the OS codes in DAP. But it is nice that I can check what other systems report from RSX. :-)
> 
> I know VMS did, that's what prompted my complaint at the time.  Specifically, I think that VMS was assuming RSTS couldn't do some X because it was RSTS.  So when RSTS DAP implemented X and reported so in the flags, VMS wasn't using it.

I think the X in question was RMS transparent access (as opposed to whole-file transfer).  RSTS implemented that as part of the Phase III work, but if I remember correctly at first VMS wouldn't use it because it ignored the capability flags.  That was one of the biggest enhancements in that DECnet/E version, so having it not supproted correctly was quite a big deal and very annoying.

	paul




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