Re: [Linuxptp-devel] [PATCH v2] Add support for DELAY_REQ and SYNC packets RX filters

[Maciek M. <ma...@ma...>]

On 28/11/2023 14:39, Erez wrote:
> 
> 
> On Tue, 28 Nov 2023 at 12:55, Miroslav Lichvar <mli...@re...
> <mailto:mli...@re...>> wrote:
> 
>     On Sun, Nov 26, 2023 at 11:10:05AM -0800, Richard Cochran wrote:
>     > The Rx filters are applied globally at the device level, but the PTP
>     > operates at the application level.  This means that the Rx filter are
>     > shared between applications.  And so you can see that one application
>     > cannot simply change the shared global settings at run time.
> 
>     This problem already exists, e.g. with ptpv2-l4-event vs ptpv2-l2-event.
>     We could say that all hardware that cannot timestamp all packets is
>     broken, but it's so common that it has to be supported. If the
>     hardware which cannot timestamp all event messages is very rare, ok,
>     maybe it's not worth the trouble.
> 
>     However, timestamping only sync messages has an advantage with very
>     large number of clients as they don't have timestamp each other's
>     delay requets and timestamping of sync messages is more reliable.
> 
> 
> PTP traffic by its nature is very low. 
> I do not see any benefit for a filter that supports only client or only
> master PTP traffic.

That argument does not hold up in the datacenter. Once you scale up to
100000 nodes @128pps trying to synchronize to a GM it's no longer what
I'd consider "very low".

Thanks,
Maciek

> 
> Perhaps the kernel should add a HWTSTAMP_FILTER_PTP_V2_ALL_EVENT,
>  that supports multiple PTP services on several layers.
> 
> Erez
> 
> 
>     -- 
>     Miroslav Lichvar
> 
> 
> 
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