[NNTP] Article Numbers Becoming Invalid (RFC 3977)

[Julien ÉLIE]

Hi Russ,

>>   Note that a previously valid article number MAY become invalid if the
>>   article has been removed.  A previously invalid article number MAY
>>   become valid if the article has been reinstated, but this article
>>   number MUST be no less than the reported low water mark for that
>>   group.
>>
>> The validity of the pointer MAY change.
>
> I wonder if we should file an erratum against that paragraph suggesting a
> rewording to use another word than invalid.  Although that paragraph does
> talk about the validity of the article number, not the validity of the
> current article pointer, so there is a subtle distinction.  But I think
> it's too subtle to be clear on a first reading.
>
> I suspect s/invalid/unavailable/ and s/valid/available/ would still be
> fairly clear and avoid the ambiguity.

Yes, I think it would be useful to file an erratum.
Even though it is rejected, it will be reviewed when a successor, if any,
to RFC 3977 comes.


>> I think the whole point is that after entering a non-empty group, 420 is
>> not a valid answer to ARTICLE without argument.  It should have been 423
>> as it was the case in RFC 977.
>
> Well, somewhat more precisely, 420 is only a valid answer to ARTICLE
> without an argument if the group was empty at the time of the GROUP
> command.  If the group was not empty but the current article is
> unavailable, 423 should be used instead.

It is indeed the explained behaviour:

   If the argument is a message-id and no such article exists, a 430
   response MUST be returned.  If the argument is a number or is omitted
   and the currently selected newsgroup is invalid, a 412 response MUST
   be returned.  If the argument is a number and that article does not
   exist in the currently selected newsgroup, a 423 response MUST be
   returned.  If the argument is omitted and the current article number
   is invalid, a 420 response MUST be returned.

We do not know the answer to give when the argument is omitted and the
article does not exist in the currently selected newsgroup!


>> And it is also what is implemented in the NNTP reference implementation,
>> INN, and probably other news servers.
>
> I'm almost tempted to propose an erratum for this, but changing a return
> code is probably more than we really should do in an erratum.

Well, I think that would not change the code at all.  The code is
currently *unspecified* in RFC 3977!

So the erratum would basically just mention the code to use.  And this
code is 423.

-- 
Julien ÉLIE

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