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

[Martin Burnicki <[e-mail]>]

FUSTE Emmanuel wrote:
> Le 06/01/2021 à 15:29, Martin Burnicki a écrit :
>> I think whether hardware timestamping is supported or not isn't related
>> to the packet format. Even NTPv4 can use timestamping in the kernel
>> driver, if the OS supports it.
> Yes but as the common time-stamping hardware only has and support only 
> one time-stamping clock and is responsible to put this clock value in 
> the outbound packet, format matter.
> You could not share the same interface with hardware time-stamping 
> between NTPv4 and PTP for this reason unless you are on custom or very 
> uncommon hardware.

However, timestamping a packet with SO_TIMESTAMP and modifying an
outgoing packet on the fly (PTP Onestep) are still 2 different things.

I know there is no clean and pretty solution to hardware-timestamp
outgoing NTP packets right now, so this could indeed be an option for a
v5 version which can have TAI support anyway.

However, if you want hardware timestamping support for NTP to yield the
level with accuracy you can yield with PTP, the question that comes to
my mind is whether a timestamper in a NIC can recognize and timestamp
NTP packets in the same way as PTP packets, and if PTP-aware switches
that measure the packet delay can also be configured to measure and
provide the delay of NTP packets.

Otherwise you can simply use PTP for such cases, and use NTP for cases
with different requirements.


Martin
-- 
Martin Burnicki

Senior Software Engineer

MEINBERG Funkuhren GmbH & Co. KG
Email: [e-mail]
Phone: [phone]
Linkedin: https://www.linkedin.com/in/martinburnicki/

Lange Wand 9, 31812 Bad Pyrmont, Germany
Amtsgericht Hannover 17HRA 100322
Geschäftsführer/Managing Directors: Günter Meinberg, Werner Meinberg,
Andre Hartmann, Heiko Gerstung
Websites: https://www.meinberg.de  https://www.meinbergglobal.com
Training: https://www.meinberg.academy