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

[Loa Andersson <[e-mail]>]

Tal and Jouni,

I'm trying to make heads and tails of this.

I think we have the three scenarios in the slides + 1 or 2 more.

0.5 - raw,   i.e. running over a network without DetNet cpabilities
1.  - Naive, i.e. running over a DetNet network
1.5 - On-path-support, on a subset of the nodes
2.  - On path support (all nodes)
3.  - Time as a service

Nat that we need to include all this in the list, I just want to have
an understanding that DetNet capabilities improve the things.

/Loa

On 2017-02-13 17:01, Tal Mizrahi wrote:
> Hi Jouni,
>
> That is a fair point. If only the PW nodes function as TCs, then indeed the accuracy will be lower.
> I added a clarification about this in slide 6.
>
> The updated slides are attached.
>
> Thanks,
> Tal.
>
>> -----Original Message-----
>> From: Jouni Korhonen [mailto:[e-mail]]
>> Sent: Thursday, February 09, 2017 10:35 PM
>> To: Tal Mizrahi
>> Cc: [e-mail]
>> Subject: Re: [EXT] [Detnet-dp-dt] DETNET Synchronization Slides
>>
>> Tal,
>>
>> I understood that in 2) the TC function would only be in the PW nodes we define
>> leaving all intermediate “normal” LSRs between PW nodes as a source of higher
>> inaccuracy. If this was not a correct understanding then the value in 2) is likely
>> too high.
>>
>> - Jouni
>>
>>
>>> On 08 Feb 2017, at 23:22, Tal Mizrahi <[e-mail]> wrote:
>>>
>>> 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?attred
>> irects=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:[e-mail]]
>>>> Sent: Wednesday, February 08, 2017 8:15 PM
>>>> To: Tal Mizrahi
>>>> Cc: [e-mail]
>>>> 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: [phone]
>>>>
>>>>> On Feb 7, 2017, at 10:51 PM, Tal Mizrahi <[e-mail]> 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
>>>>> [e-mail]
>>>>> https://www.ietf.org/mailman/listinfo/detnet-dp-dt
>>>
>
>
>
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-- 


Loa Andersson                        email: [e-mail]
Senior MPLS Expert                          [e-mail]
Huawei Technologies (consultant)     phone: [phone]