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

[FUSTE Emmanuel <[e-mail]>]

Le 06/01/2021 à 11:50, Martin Burnicki a écrit :
> Philip Prindeville wrote:
>>> On Jan 5, 2021, at 9:09 AM, Martin Burnicki<martin.burnicki=[e-mail]>  wrote:
>>>
>>> For NTP, things are different. There is a huge base of NTPv4
>>> installations, and making NTPv5 basically compatible with v4 would IMO
>>> strongly increase the acceptance of NTPv5.
The "basically" mean nothing. Is is 100% compatible or not compatible. 
It is NTPv4 or NTPv5. The "not so different" between v3 and v4 was much 
a source of problems than an adoption catalyst.
I even view it in the opposite for a psychological/marketing acceptance 
point of view: being  v4 compatible is so restrictive for v5 that people 
would prefer to stick to v4 as v5 would give nothing more than v4 
(unless being an expert to understand the difference/gain).
Do we want to do a NTPv4 revision or NTPv5 ?
>> The logical corollary to this argument is that because there ARE a lot of servers, it’s not unreasonable to think that there will be a lot of both NTPv4 and NTPv5 servers co-existing in the future, and the user is free to peer with either.
> So you think it's not necessary to upgrade v4 nodes to v5, as it has
> been done from v3 to v4? Simply systems should stick with v4 and only
> enhanced system should start using v5?
>
> In this case, wouldn't it be better to start defining a completely new
> protocol and e.g. call it "Extended Time Protocol", which can be chosen
> instead of NTP? This would be similar to PTP, which you can use instead
> of NTP. ;-)
>
>> Which eliminates the need for NTPv5 servers to also speak NTPv4.
> If you have a large network with different types of client you will need
> to provide NTPv4 and "ETP" (AKA NTPv5) if NTPv5 has requirements that
> are not needed and can't be supported by some clients.
But the "can't" is wrong as long as the offset is always transmitted and 
for the "need" argument, the same clients would have stick to 
time/daytime service if it is a real one.
A v5 server could still provide v4 frame and for v4 clients if needed 
but without hw times-stamping support which it would reserve for v5 
clients if it has some actives. But it is implementation and policy details.

Emmanuel.