[ntp:hackers] NTP cores in authistrustedip.

Harlan Stenn stenn at ntp.org
Fri Apr 22 02:22:25 UTC 2016

Martin Burnicki writes:
> A side-effect of autokey is that it transfers the current TAI offset to
> the clients, and I know some folks who explicitly use autokey for this
> purpose.
> Harlan, I know this could also be achieved by using a leap second file,
> and that there's a script somewhere which tries to download an upgrade
> the leap second file automatically. ;-)
> However, using autokey for this is much more elegant, IMO. Once you
> have configured your server and clients properly you don't have to
> care if there's a cron job which runs some script periodically, if the
> download site is reachable via http or ftp, etc.

With the known weaknesses of autokey, I don't see how *any* use of
autokey can be considered "elegant".

But this is exactly the sort of thing that could go into a new extension
field, and I'd love to see what other information we could usefully put
there, too.

Right now the list of interesting items I can think of is:

- TAI offset
- a bit signifying "I'm in interleave mode"

We don't have enough room to encode the TAI offset into a 4-byte EF, so
if we use an 8-byte EF that gives us the low-order data byte for the TAI
offset, and the high-order bit for interleave mode, and that gives us
another 23 bits to use for other things.


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