Discussion:
[Linuxptp-devel] Config option "assume_two_step"
Jesuiter, Henry (ALC NetworX GmbH)
2016-09-21 09:20:49 UTC
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Hello,

recently I stumbled upon the "assume_two_step" config option (we accidentally set this flag two '1' ;-)). As I read in the source, this is used to skip the TWO_STEP flag inside the PTP messages, and just return '0' for one_step() status. Could someone please explain, why this option is there? Since we already have the TWO_STEP flag inside the messages, I can't see any reason why we would need that option. Is it just a historical relic or are there other reasons for this flag.

Best regards
Henry

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Delio Brignoli
2016-09-21 11:44:42 UTC
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Hello Henry,

If I recall correctly, assume_two_step is there to accommodate section 11.4.2.3 of 802.1AS-2011 where it says that the twoStepFlag is “Reserved as TRUE, ignored on reception”.

Regards
--
Delio
Post by Jesuiter, Henry (ALC NetworX GmbH)
Hello,
recently I stumbled upon the "assume_two_step" config option (we accidentally set this flag two '1' ;-)). As I read in the source, this is used to skip the TWO_STEP flag inside the PTP messages, and just return '0' for one_step() status. Could someone please explain, why this option is there? Since we already have the TWO_STEP flag inside the messages, I can't see any reason why we would need that option. Is it just a historical relic or are there other reasons for this flag.
Best regards
Henry
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Keller, Jacob E
2016-09-21 20:53:39 UTC
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-----Original Message-----
Sent: Wednesday, September 21, 2016 4:45 AM
Subject: Re: [Linuxptp-devel] Config option "assume_two_step"
Hello Henry,
If I recall correctly, assume_two_step is there to accommodate section
11.4.2.3 of 802.1AS-2011 where it says that the twoStepFlag is “Reserved as
TRUE, ignored on reception”.
Regards
This is correct. There was a switch that follows this standard and was not properly setting twoStep so we were treating it like a oneStep mode when the switch expected us to treat it like a twoStep message. This was added to support that bad implementation, because of the way the standard is worded.

Thanks,
Jake
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