Re: [v6ops] Fw: New Version Notification for draft-elkins-6man-ipv6-pdm-dest-option-04.txt

"Ackermann, Michael" <> Mon, 28 October 2013 16:13 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 1536621E8095 for <>; Mon, 28 Oct 2013 09:13:24 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -6.035
X-Spam-Status: No, score=-6.035 tagged_above=-999 required=5 tests=[AWL=-0.036, BAYES_00=-2.599, J_CHICKENPOX_13=0.6, RCVD_IN_DNSWL_MED=-4]
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id dssZnZ0JDLgy for <>; Mon, 28 Oct 2013 09:13:23 -0700 (PDT)
Received: from ( []) by (Postfix) with ESMTP id 2957821E8091 for <>; Mon, 28 Oct 2013 09:13:18 -0700 (PDT)
Received: from (ZixVPM []) by (Proprietary) with ESMTP id 5AAB12FF652 for <>; Mon, 28 Oct 2013 11:13:17 -0500 (CDT)
Received: from (unknown []) by (Proprietary) with SMTP id 23FA3307427; Mon, 28 Oct 2013 11:13:16 -0500 (CDT)
Received: from (unknown []) by IMSVA80 (Postfix) with ESMTP id 0CF194F804D; Mon, 28 Oct 2013 12:02:52 -0400 (EDT)
Received: from (unknown []) by (Postfix) with ESMTP id E76C24F8049; Mon, 28 Oct 2013 12:02:51 -0400 (EDT)
Received: from ( by ( with Microsoft SMTP Server (TLS) id 14.1.438.0; Mon, 28 Oct 2013 12:13:14 -0400
Received: from ([fe80::fdcb:603d:469e:b1db]) by ([fe80::f13e:83e4:1dae:5345%10]) with mapi id 14.01.0438.000; Mon, 28 Oct 2013 12:13:13 -0400
From: "Ackermann, Michael" <>
To: Ray Hunter <>
Thread-Topic: [v6ops] Fw: New Version Notification for draft-elkins-6man-ipv6-pdm-dest-option-04.txt
Thread-Index: AQHO0OGzc1wNgnhly0SIwwwBJHHHZZoEfl4ggAF03YCABFViAA==
Date: Mon, 28 Oct 2013 16:13:13 +0000
Message-ID: <>
References: <> <> <> <> <> <> <> <> <>
In-Reply-To: <>
Accept-Language: en-US
Content-Language: en-US
x-originating-ip: []
x-tm-as-product-ver: SMEX-
x-tm-as-result: No--39.910400-8.000000-31
x-tm-as-user-approved-sender: No
x-tm-as-user-blocked-sender: No
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Cc: v6ops WG <>, 6man WG <>, "" <>
Subject: Re: [v6ops] Fw: New Version Notification for draft-elkins-6man-ipv6-pdm-dest-option-04.txt
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: v6ops discussion list <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Mon, 28 Oct 2013 16:13:24 -0000

Hey Ray

It appears your experiences with Time Synch and Stratum levels are different than mine.   In the older Telecom and Voice World Stratum was a great indicator of clocking accuracy.   Still is as far as I know.   This was always true with or without NTP in the picture.   
And whenever we had two Stratum 0's or 1's, be they the same or different masters, they WOULD be in synch.   We never had a situation that was an exception to that, with or without NTP.  



-----Original Message-----
From: Ray Hunter [] 
Sent: Friday, October 25, 2013 1:38 PM
To: Ackermann, Michael
Cc: Nalini Elkins; v6ops WG; 6man WG;;;
Subject: Re: [v6ops] Fw: New Version Notification for draft-elkins-6man-ipv6-pdm-dest-option-04.txt

> Ackermann, Michael <>
> 25 October 2013 01:44
> Ray
> Your Comment: 
> No. I think what I said was that the level of certainty in your measurements is dependent on the level of synchronisation of the 2 clock sources if you are calculating a delta of timestamp of clock 1 - timestamp clock 2.
> My Response:
> Then it sounds like we are in agreement.   Given the appropriate stratum level at both nodes, the desired level of time synchronization is achieved. 
No. We are not in agreement.

Stratum is an indication of how far down you are in the hierarchy from any NTP Stratum 0 clock.

It says nothing about whether your stratum 0 and my stratum 0 are synchronised.

We could both be running caesium clocks, and there could still be an offset if I don't set my reference time of my caesium clock the same as your reference time. When talking about microsecond or picosecond timing that will almost certainly be significant.

You really need to know that the true provenance of the clock source is identical in order to make PDM 1 calculations, not just the stratum.

Hence my comment to couple some sort of "clock ID" to the timestamp.
> Your Comment: 
> I think it might be instructive to go back and look at high school physics books on making measurements, precision, accuracy, and error estimations, especially when taking the difference of two measurements, or making other calculations on top of raw observations
> My Response:  Not sure exactly what this means but I can say that this sounds like theoretical doubt that time synchronization will not work properly in geographically dispersed environments?    I can tell you that it does in our experiences and that the surrounding protocols/implementations are crafted to account for such vicissitudes.  
> I will say that I have no field experience with DCF-77 sources, only GPS and Cesium.  
> Your Comment:
> Equally a stratum 0 clock can be free running if it loses it's radio signal.
> My Response: 
> This comment sort of confused me as well, but suffice to say, if any component is broken, results will be impaired.   Obviously this is not limited to the time synch subject.  
> Finally, your comment about "Middleboxes".    I hope it can be as simple to accommodate as you describe.   My concern is that if there are numerous middleboxes, the fields may get repetitively overlaid, or there will need to be so many separate fields, we could incur excessive complexity or overhead.    Given that we can accomplish this with a workable solution, I am certainly all for it.   
> The more information I can have to manage networks and solve problems, the better!
> Thanks again for your thoughts, inputs and questions!
> Mike

The information contained in this communication is highly confidential and is intended solely for the use of the individual(s) to whom this communication is directed. If you are not the intended recipient, you are hereby notified that any viewing, copying, disclosure or distribution of this information is prohibited. Please notify the sender, by electronic mail or telephone, of any unintended receipt and delete the original message without making any copies.
 Blue Cross Blue Shield of Michigan and Blue Care Network of Michigan are nonprofit corporations and independent licensees of the Blue Cross and Blue Shield Association.