[Info-vax] Unexpected DECnet Phase IV functionality with possible captive account implications

[Simon Clubley]

On 2021-05-10, Stephen Hoffman <seaohveh at hoffmanlabs.invalid> wrote:
>
> Captive doesn't get to write anywhere outside of very targeted 
> directories, and then only with constraints. See below for more on the 
> constraints.
>

Captive accounts can be privileged. In fact, that's the whole point
of them for a good range of usage cases.

>
> And there's a reason I keep writing comments about the problems of 
> continued use of DECnet...
>

Well, I can now say that the FAL protocol is one of the most ugly
designs I have seen. It's the type of protocol that only an assembly
language programmer could think was elegant. :-)

The design is full of optional fields and bitfields listing which
fields are present. This has to be examined before looking for each
of the remaining (possibly omitted) fields and this has to be done
for every field in the FAL messages which implement this.

NSP isn't much better with messages that may or may not have one
or both ACK fields and you tell this by looking to see if the top
bit of the next 16-bit word is set.

I find that amusing given the amount of redundancy you have in the
routing layer part of a DECnet Ethernet packet.

These are protocols that were designed in _very_ different times...

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.