Re: [Ntp] Antw: [EXT] Going forward with NTP ‑ v5, v4 and approach

On 8/19/2022 12:26 AM, Ulrich Windl wrote:
>>>> <kristof.teichel=40ptb.de@dmarc.ietf.org> schrieb am 18.08.2022 um 13:09
> in
> Nachricht <OFBAE2F5D9.2E42DB42-ONC12588A2.00362BE6-C12588A2.003D5155@ptb.de>:
> ...
>> 4) Are mode 6 exchanges (any modes other than timing packets really) part
>> of "the protocol"? Specifically, do they share a version number, or get
>> their own?
>> Again, I would have assumed that obviously, one divides a protocol (with
>> version number) into modes. I.e., there would be NTPv4, with one of its
>> modes being NTPv4‑mode6.
>> But one could also say that NTP‑mode6 is kinda its own protocol, and then
>> say something like "we are currently up to v4 for NTP‑mode2/3, but only up
>> to v2 for NTP‑mode6"; I find this is asking for trouble, but one could do
>> it. There is a strong point to be made then that this way, the mode would
>> be its own protocol and should have its own specification.
> 
> The problewm IMHO is that the VN field in the NTP packet is used to specify
> how to parse it. So an NTPv4-mode6 request cannot use the same VN field to
> specify ist version number (when independent from the core NTP timing
> ptotocol).

Please give an example of how this is true.

> There are claims saying an NTP packet can always be parsed whatever the VN
> field is, however.

If v5 breaks with history and uses an incompatible base packet structure 
this is probably true if one wants to have per-version parsing engine.

TANSSAAFL.  If you want compatibility, be compatible.  If you want new 
features to be added *and* maintain compatibility, that's likely trivial 
with v5 with regards to a v4 or v5 server.

If you don't care about v4/v5 compatibility, then that's your choice, too.

No packet format that uses EFs will be able to talk with stock pre-v4 
servers.

> ...
> 
> Regards,
> Ulrich
> 
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Harlan Stenn <stenn@nwtime.org>
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