Re: [LEAPSECS] Introduction of long term scheduling

From: Zefram <zefram_at_FYSH.ORG>
Date: Mon, 8 Jan 2007 10:59:25 +0000

Poul-Henning Kamp wrote:
>We certainly don't want to transmit the leap-second table with every
>single NTP packet, because, as a result, we would need to examine
>it every time to see if something changed.

Once we've got an up-to-date table, barring faults, we only need to check
to see whether the table has been extended further into the future.
If we put the expiry date first in the packet then that'll usually be
just a couple of machine instructions to know that there's no new data.

If an erroneous table is distributed, we want to pick up corrections
eventually, but we don't have to check every packet for that. Not that
it would be awfully expensive to do so, anyway.

>Furthermore, you will not getaround a strong signature on the
>leap-second table, because if anyone can inject a leap-second table
>on the internet, there is no end to how much fun they could have.

This issue applies generally with time synchronisation, does it not?
NTP has authentication mechanisms.

-zefram
Received on Mon Jan 08 2007 - 03:00:29 PST