ietf-nntp Section 11.5 - NEWNEWS

[Paul Overell]

In article <20001121124113.F70107 at demon.net>, Clive D.W. Feather
<clive at demon.net> writes
>Paul Overell said:
>>> + The date and time are given in the server's approximation to UT
>>> + (otherwise known as GMT). The server is not required to track leap
>>> + seconds or UT/TAI/UTC variations exactly, nor need the server's clock
>>> + be accurate to within 1 second.
>
>> I think invoking UT/TAI/UTC/ is muddying the waters.  It's in UTC (not
>> UT, not TAI, not POSIX).
>
>How do you know ? That's one of the issues.
>

Because in 1986 (the date of RFC977) the basis of civil time was (and
still is) UTC.  Futhermore, so far as NEWNEWS and NEWGROUPS are
concerned it is clear from RFC977 that "GMT" is purely referring to a
timezone not a timescale.  

>3.7.1

>The time is assumed to be in the server's timezone unless the
>token "GMT" appears, in which case both time and date are evaluated
>at the 0 meridian.

Therefore DATE should return UTC so as to be compatible with the
NEWSNEWS and NEWGROUPS commands.


>> Saying what accuracy is not required doesn't
>> say what accuracy is required.  I suggest:
>> 
>>         The date and time are given in UTC.  The date and time SHOULD be
>>         accurate.
>> 
>> Using "SHOULD" gives the server the get-out if they can't support leap
>> seconds or if their clock drifts a bit, but if they can get it right
>> then they SHOULD.
>
>If we give a quantity, the client knows how much slack to allow when doing
>the DATE/NEWNEWS thing. I think that's a good idea.
>

I fully agree that recommending that clients use some slack with NEWNEWS
and NEWGROUPS is a good idea - that's just good defensive programming.  

I'm far less happy about specifying an explicit tolerance on a server's
clock.  If the server has the same inaccuracy as the client slack then
we are right at the edge of losing articles in NEWNEWS.

Far better if clients use slack but servers get it right (for some
unspecified value of "right").


Regards

-- 
Paul Overell                                             T U R N P I K E