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Re: [Detnet-dp-dt] [EXT] Re: DETNET Synchronization Slides

Tal Mizrahi <talmi@marvell.com> Thu, 09 February 2017 07:22 UTC

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From: Tal Mizrahi <talmi@marvell.com>
To: Jouni Korhonen <jouni.korhonen@broadcom.com>
Thread-Topic: [EXT] Re: [Detnet-dp-dt] DETNET Synchronization Slides
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Date: Thu, 9 Feb 2017 07:22:43 +0000
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Subject: Re: [Detnet-dp-dt] [EXT] Re: DETNET Synchronization Slides
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Hi Jouni,

Sorry for not explaining the accuracy numbers on slide 6 further. I made some changes following the discussion, and also added notes saying that the accuracy will depend on the network topology and on the number of hops.

Regarding approach 2, I believe sub-microsecond accuracy can certainly be achieved using transparent clocks in a real network. There are quite a few publications that show this. Here are a couple: 
- For example, China Mobile have revealed in a keynote lecture in ISPCS 2014 that they have measured an accuracy of 266 ns over 30 hops of transparent clocks. Unfortunately, this presentation is not in the public domain, but a short version of it is available  (https://www.ietf.org/mail-archive/web/tictoc/current/pdfp9ceHphbcE.pdf). 
- Another example: http://wwwen.zte.com.cn/endata/magazine/ztecommunications/2010Year/no3/articles/201009/t20100913_191838.html
But again, this entirely depends on the nature of the network.

Regarding approach 1, the accuracy will entirely depend on the network topology (the number of hops, the physical distance, the type of intermediate nodes, the delay variation). Hundreds of microseconds is just an example. Some of the research I took part in showed that in a multi-site public cloud network you can achieve a precision on the order of hundreds of microseconds using PTP without on-path support (https://sites.google.com/site/talmizrahihome/files/TaaSInfocomFinal.pdf?attredirects=0). But again, this entirely depends on the nature of the network.

Please let me know if there are further comments.

Thanks,
Tal.


>-----Original Message-----
>From: Jouni Korhonen [mailto:jouni.korhonen@broadcom.com]
>Sent: Wednesday, February 08, 2017 8:15 PM
>To: Tal Mizrahi
>Cc: detnet-dp-dt@ietf.org
>Subject: [EXT] Re: [Detnet-dp-dt] DETNET Synchronization Slides
>
>External Email
>
>----------------------------------------------------------------------
>Thanks Tal,
>
>Didn’t we also agree adjusting the slide 6 “typical accuracy” numbers:
>1) <1ms or hundreds of us
>2) <tens of us
>3) <1us
>
>- Jouni
>
>
>--
>Jouni Korhonen, Broadcom Ltd.
>M: +1-408-391-7160
>
>> On Feb 7, 2017, at 10:51 PM, Tal Mizrahi <talmi@marvell.com> wrote:
>>
>> Hi,
>>
>> The slides from today’s weekly meeting are attached.
>> I slightly updated them after the meeting based on the comments.
>>
>> Cheers,
>> Tal.
>> <Synchronization in
>DETNET.pptx>_______________________________________________
>> Detnet-dp-dt mailing list
>> Detnet-dp-dt@ietf.org
>> https://www.ietf.org/mailman/listinfo/detnet-dp-dt

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