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Re: [TICTOC] Enterprise profile update

"Dowd, Greg" <Greg.Dowd@microsemi.com> Tue, 08 April 2014 20:49 UTC

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From: "Dowd, Greg" <Greg.Dowd@microsemi.com>
To: Richard Cochran <richardcochran@gmail.com>, Kevin Gross <kevin.gross@avanw.com>
Thread-Topic: [TICTOC] Enterprise profile update
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Date: Tue, 08 Apr 2014 20:49:28 +0000
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References: <CACQYgzE106JaKArgc=3HKkKcrdvSy5PmK-A0=_ZMdfrFUJbrtQ@mail.gmail.com> <20140405112034.GM22106@netboy> <20140405133748.GB4566@netboy> <CALw1_Q3hNRNpHzQ=1z0XRTqvcvm2W7=Gm_ZWa2UJT-BqYTvmZw@mail.gmail.com> <CF68E7A8.7488B%lmontini@cisco.com> <1D3F6A7C-AD27-4A63-9F63-41D9929AE285@owczarek.co.uk> <20140408144527.GA5087@netboy> <CALw1_Q1ObS652A+GazmmB4gfkNnnJ4DcsiJ5PoQCd6wxNw-mrA@mail.gmail.com> <20140408200830.GA30453@netboy>
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Cc: "tictoc@ietf.org" <tictoc@ietf.org>
Subject: Re: [TICTOC] Enterprise profile update
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I don't think unicast negotiation will go away.  16.1 works quite well for managed networks.  An original premise here was that we were trying to move to support an "Internet" profile.  From that perspective, the ntp protocol has had the same requirements and handled them pretty well, although we all debate certain aspects.  One big problem is scaleability.  It would be ideal for ptp servers to be stateless.  Default profile is fine for that.  But the overhead of the multicast delay request-response system is scales poorly.  So, the hybrid profile.  This allows the slaves to be bootstrapped without configuration.  They register the listen, similar to ntp multicast, they discover ptp service stream and then act appropriately.  They could just jam the offset occasionally, they could have a short "ranging" session for path delay (again, like ntp multicast) or they could mobilize an association and perform ranging functions at a rate similar to the server transmission rate.  One other note about having a profile is to correct a profile nit which I see almost as a bug.  Currently, the default profiles mandates that event messages originate from 319 while data messages can originate from any source port.  This limitation provides little value in my opinion and breaks NAT.  Obviously, a non-PTP aware gateway device doing NAT opens a whole other can of worms but protocol, or data flow, is one layer of operation and performance is another.




-----Original Message-----
From: TICTOC [mailto:tictoc-bounces@ietf.org] On Behalf Of Richard Cochran
Sent: Tuesday, April 08, 2014 1:09 PM
To: Kevin Gross
Cc: tictoc@ietf.org
Subject: Re: [TICTOC] Enterprise profile update

On Tue, Apr 08, 2014 at 01:09:58PM -0600, Kevin Gross wrote:
> 
> The objection I've heard to 16.1 is that it imposes arguably 
> unnecessary overhead in setting up unicast delay request/response. It 
> is simpler for a master just to know (based on profile) that when it 
> receives a unicast delay request, it should simply generate a unicast response to the sender.
> If the enterprise profile is defined to work in this way, a slave can 
> switch mode on the fly and quickly compare results between unicast and 
> multicast and determine the best mode of operation.

Yes, I agree that 16.1 is a real PITA to implement. However, that is what is in the standard. It seems strange to me that profiles should try and second guess aspects that are already standardized. The more profiles do that, the harder it gets for humble implementations to support the many variations.

Is there a feeling that 16.1 was a mistake, is not implemented in real life, and is disappearing in the next 1588 edition?

If so, I'll surely *not* bother to implement it in linuxptp.

Thanks,
Richard

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