ietf-nntp Section 11.5 - NEWNEWS

Charles Lindsey chl at clw.cs.man.ac.uk
Fri Nov 17 03:26:30 PST 2000


In <ylaeazmy6f.fsf at windlord.stanford.edu> Russ Allbery <rra at stanford.edu> writes:


>Paul Overell <paulo at turnpike.com> writes:
>> Clive D.W. Feather <clive at demon.net> writes

>>> + The date and time are given in the server's approximation to UT
>>> + (otherwise known as GMT).

>No, it's not; it's UTC.  The only reason why it was called GMT was because
>folks didn't understand the technical difference between GMT and UTC.
>Most server implementations that I'm familiar with use gmtime to obtain
>the information, and on nearly all Unix systems this will return UTC (on
>some, it will return TAI).

May I suggest

+ The date and time are given in the server's approximation to UTC
+ (commonly referred to as GMT).

And will somebosy please explain to me what "TAI" is?

>>> + 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.

>As long as it's clear that if the server is actually keeping TAI, the news
>server software isn't required to convert that to UTC.  We don't want to
>go there, and it's very reasonable (and more useful for some applications)
>to set a Unix system clock to track TAI instead of UTC.  I know quite a
>few people who do so.

I don't think we need to care if the server is out by several minutes
even, since it should not concern us. That is more than enough to work out
what the server's time zone is.

The only command that cares about time is NEWNEWS. If we ask for all
articles received on the server since 001116 031219, then what we actually
want is "all articles received since the last time I asked you, which was
at 001116 031219 according to my reckoning". The problem is that the time
quoted in the NEWNEWS came from the clock on MY machine, and the server
will respond according to the clock on ITS machine. So both machines need
to be accurate for perfect performance. A more realistic solution would be
for people to include an overlap (a few minutes) in the time they give in
the NEWNEWS command, since it does little harm if a few duplicate
Message-IDs are received.

Maybe there should be a NOTE to suggest exactly that.

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
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