[Ntp] Re: NTPv5 extension field greasing

[Danny Mayer <[e-mail]>]

> On Tue, Jan 20, 2026 at 12:19 PM David Venhoek 
> <david=[e-mail]> wrote:
>
>     Hi All,
>
>     I have written a proposal to include greasing of the extension field
>     mechanism in NTPv5. This is essentially clients sending random
>     extension fields to servers to ensure servers properly ignore unknown
>     extension fields and still respond.
>
>     Doing this preserves the use of extension fields for probing for new
>     features in the future, avoiding the need for another
>     upgrade-signaling mechanism as is currently needed for the NTPv4 to
>     NTPv5 transition.
>
>     I have taken the liberty of already proposing an explicit set of
>     extension field identifiers for these fields. These were selected with
>     the goals that
>     a) there shouldn't be too obvious patterns, to dissuade explicit
>     filtering,
>     b) and existing large contiguous blocks of extension field type
>     codepoints are not broken up.
>
None of this is necessary. An extension field is always ignored if not 
present. If you want to add an extension field for research or 
development you can do so without affecting anyone else. If you want to 
reserve extension field ID's then use a range, preferably in the upper 
limit of the values.

Danny