Re: PTP/Syncronized Ethernet maturity

["m.Taichi via NANOG" <nanog () nanog org>]

Hi Geir,

Can we say, from your production network experiences across Asia and
Europe, that getting synchronization clock signal via GNSS receiver
directly on each cell site is a much more reliable, stable, and simpler way
than getting it by network-based PTP? Especially when there is WDM link
used in between the BC and Slave Clock?

Why does WDM link cause path asymmetry? I thought the optical fibers carry
forward link and reverse link are almost equal in length (distance). Aren't
they?

What are your solutions to overcome the PTP synchronization instability
problems in your TDD 4G/5G networks?

Thanks and best regards,
Taichi


On Tue, Sep 8, 2020 at 11:09 PM geir egeland via NANOG <nanog () nanog org>
wrote:

> We have mobile NWs in both Asia and Europe and also experience a lot of
> issues with PTP, - almost with every vendor.
> The instabilities, SW-bugs etc. related to PTP seems to indicate that very
> little testing of this code has been done in production networks. In some
> deployments we have been able to produce a clock service by installing GNSS
> on the cell-site. However, in other countries there are regulatory
> directives that the phase sync must be PTP/Network based.
>
> Currently, the optical domain is causing us huge problems when we try to
> engineer a T-BC/PTP solution. This is due to the path asymmetry that exist
> in the WDM/fiber domain. In some networks we have a lot of DCF in the fiber
> path and the only way we can get visibility in the asymmetry on these fiber
> hops is to measure in both direction:(
> Also, running T-BC over WDM/OTN will simply not work as the phase error
> introduced more or less eats up the phase error budget for 4G/5G
> TDD-service.
>
> best regards,
> Geir
>
> On 5 Sep 2020, at 00:17, Macho Pellegrini via NANOG <nanog () nanog org>
> wrote:
>
> Hello everybody,
>
> We have deployed PTP in our mobile NW since late 2019 as a part of the
> 4G/5G, however we are seeing a lots of instabilities and interop issues, a
> lot of the issues have ended up with SW bugs in the OS, I have no specific
> question, however I got the impression that the technology/protocol is not
> yet mature, anybody here got his hands dirty with PTP?
>
> Thanks,
> MP