Re: [Ntp] CLOCK_TAI (was NTPv5: big picture)

[Hal Murray <[e-mail]>]

[e-mail] said:
> NTP is used for synchronization of various clocks. Most of them are based on
> UTC. NTPv5 cannot support only TAI. 

This is a tangled area.

I think that a TAI only NTPv5 protocol would be much cleaner and easier to 
document.  Yes, I agree that we need a story for UTC, but the answer doesn't 
have to clutter up an RFC for NTPv5.

All the kernel and/or libc need to convert TAI to/from UTC is the TAI-UTC 
offset (a small integer) and the date of the next leap second, a flag for 
insert/delete/none, and the valid-until date of the info.

We could provide that data in an extension.  The same extension would allow a 
NTPv4 server to provide clients with enough info to let current UTC based 
kernels provide TAI and/or leap when appropriate.

We could provide that data in a new protocol.  Or a new packet type on the NTP 
port.  Or via DNS.

An extension would piggyback on whatever we use to authenticate NTPv5.  DNSSEC 
would authenticate the DNS approach.

If we implement this on the network, we should be sure to emphasize that the 
data only changes every 6 months and that we expect clients to remember the 
answer rather than ask every time.

We could provide code that lets systems process leap-seconds.list
ntpd already does.
A copy of the leap seconds file is included by the Time Zone project and 
distributed by IANA.  Most distros are already setup to keep the time zone 
info up to date.  It should be simple for the leap file to go along for the 
ride.  Debian already does it.

-- 
These are my opinions.  I hate spam.