[Ntp] Antw: [EXT] Re: Antwort: Re: Symmetric mode

[Ulrich Windl <[e-mail]>]

>>> Danny Mayer <[e-mail]> schrieb am 22.09.2022 um 01:30 in
Nachricht <[e-mail]>:
> See below.
> 
> On 9/20/22 11:26 AM, kristof.teichel=[e-mail] wrote:
...
>> >It's extremely useful, particularly when you end up in orphan mode or
>> >just need to make sure that all systems in the local network are
>> >synchronized.
>>
>> 1) You say particularly. Is it useful in any other known use-cases?
> Yes. Any set of systems that need to ensure that they are synchronized 
> together can take advantage of this. Most of the time you would want to 
> do this if they are all on a LAN. Broadcast, Multicast and Symmetric 
> Peer modes are particularly useful on a LAN.

Maybe NTPv5 should talk about what parts of the mechnisms MUST be supported, what SHOULD be supported and what MAY be supported.
NTS does not support peering, chrony does not support multicast, etc.

>> 2) Also, how often do we think the former case happens? A feature 
>> might be incredibly useful in the case of heavy acid rain, but that 
>> alone is not reason to implement it. Also, see 3)

See above.

> 
> I can't answer that since I don't maintain those kinds of systems. If 
> you loose your external internal internet connections, which we know 
> happens from time to time, having internal systems synchronized with 
> each other keeps things working in a coordinated fashion.

Actually no 8-(

We had a problem when the servers lost connection to the stratum-1 servers (and it wasn't noticed over the weekend).
Then the peering servers would step slowly towards stratum 16, eventually drifting apart.


> 
>> 3) I'm increasingly approaching NTP from a viewpoint of metrological 
>> traceability (this is important to PTB as an NMI, I intend to 
>> contribute text suggestions for documents in the future). I believe 
>> there is a strong case to be made for a simple hierarchical approach 
>> (i.e. get time from one, pre-specified server, and secure it with NTS 
>> or other authenticity-protection) if traceability is what one is 
>> thinking about. Under this perspective, the latter use-case honestly 
>> seems problematic (traceability mostly goes out the window once you 
>> don't have a "source" and instead are keeping several equal-level 
>> partners synchronous, IMO).
> For some cases simple hierarchical approach is simpler. PTP does that. 

I think the idea of PTP is that the whole environment is under some common control/management. For NTP that is typically not true. It also seems to me that PTP demands that the master clock never fails. (I did not dig into the depths of PTP so far)

> NTS was trimmed down to only handle client/server mode in order to get 
> it out the door. There's nothing to prevent other modes using NTS, 
> though Broadcast and Multicast might more be tricky to implement.

While still desirable. Any progress on such?

>>
>> >You really need to take the time to understand it.
>>
>> I'll reiterate my point from a few weeks ago that I would prefer if we 
>> keep our tone constructive in WG exchanges.
>> This seems like a pretty broad dismissal of a bunch of statements and 
>> a hard assumption of ignorance.
>> Can you give us hints how you find Miroslav's statements 
>> wrong/misleading (and which ones) so that the rest of us can be part 
>> of the conversation?
> This was not meant as any disrespect of Miroslav or anyone else. I can 
> only point to documentation and explanations of why symmetric peer mode 
> is useful. Dave Mills spent years conducting research and development on 
> this and he has written plenty of papers on this.

And he was rather successful making you believe that is's useful and needed ;-)

...

Regards,
Ulrich