Re: [Ntp] ntp-over-ptp concerns

[Rodney Cummings <[e-mail]>]

Hi Miroslav,

There’s a very basic statement in 6.6.2 of 1588-2019:
                “MASTER: The PTP Port is the source of time on the PTP Communication Path served by the PTP Port.”

What is the source of time in NTP-over-PTP?

You seem to be saying “It doesn’t comply with any state in 1588”. If so, that proves my point.

Rodney

From: Miroslav Lichvar <[e-mail]>
Sent: Tuesday, March 19, 2024 4:53 AM
To: Rodney Cummings <[e-mail]>
Cc: Rodney Cummings <rodney.cummings=[e-mail]>; NTP WG <[e-mail]>; Doug Arnold <[e-mail]>
Subject: Re: [Ntp] ntp-over-ptp concerns

On Mon, Mar 18, 2024 at 04: 34: 28PM +0000, Rodney Cummings wrote: > As one recent example, refer to this liaison from IEEE 1588 WG to the IEEE 802. 1 WG, approved unanimously in the 1588 WG: > https: //urldefense. com/v3/__https: //www. ieee802. org/1/files/public/docs2024/liaison-ieee1588-P8021ASebPARcomments-feb24. pdf__;!!I5pVk4LIGAfnvw!hc1dbVhbcmFog6KzMtbqm_el0YwqJLVFQsW-iUJst2U2YGne_TFIfRzjAZJZVNrw2XutASBawURx6Zym8rSLpJSr$
ZjQcmQRYFpfptBannerStart
This Message is From an External Sender: Use caution opening files, clicking links or responding to requests.
ZjQcmQRYFpfptBannerEnd

On Mon, Mar 18, 2024 at 04:34:28PM +0000, Rodney Cummings wrote:

> As one recent example, refer to this liaison from IEEE 1588 WG to the IEEE 802.1 WG, approved unanimously in the 1588 WG:

>             https://urldefense.com/v3/__https://www.ieee802.org/1/files/public/docs2024/liaison-ieee1588-P8021ASebPARcomments-feb24.pdf__;!!I5pVk4LIGAfnvw!hc1dbVhbcmFog6KzMtbqm_el0YwqJLVFQsW-iUJst2U2YGne_TFIfRzjAZJZVNrw2XutASBawURx6Zym8rSLpJSr$<https://urldefense.com/v3/__https:/www.ieee802.org/1/files/public/docs2024/liaison-ieee1588-P8021ASebPARcomments-feb24.pdf__;!!I5pVk4LIGAfnvw!hc1dbVhbcmFog6KzMtbqm_el0YwqJLVFQsW-iUJst2U2YGne_TFIfRzjAZJZVNrw2XutASBawURx6Zym8rSLpJSr$>

> Background: 802.1AS is a profile of 1588 that is layer-2 multicast, and allows for BMCA to be disabled. When BMCA is disabled, the 802.1 WG wanted an option to disable the Announce message as well. 1588-2019 requires Announce in 9.5.8 and elsewhere, so both WGs faced the same sort of problem as we are discussing here. The 802.1 WG has agreed to work with the 1588 WG on the problem, and the solution will ultimately involve cooperative projects in both standards.



Could you please elaborate how this impacts NTP over PTP? In 9.5.8 of

1588-2019 the only thing I see that could be relevant is "A PTP Port

in the MASTER state shall periodically transmit an Announce message",

but NTP over PTP doesn't violate that because it doesn't need a port

to be in the MASTER state, unlike 802.1AS.



I looked at all sentences containing the word "announce" (397

instances), but I didn't see anything that would conflict with NTP

over PTP.



> The point is that if one WG has valid reasons to violate the requirements in 1588, that’s okay, but it requires a project in the 1588 WG in order to loosen the requirements.



Again, in my (probably very limited) knowledge NTP over PTP is not

violating any requirements of 1588 and certainly it's not doing that

intentionally. If you know it is violating any requirements, please

describe how exactly. It might be obvious to you, but it's not obvious

to me.



--

Miroslav Lichvar