Re: [v6ops] draft-elkins-v6ops-ipv6-pdm-recommended-usage-00

[Mark ZZZ Smith <[e-mail]>]

>________________________________
> From: Bill Jouris <[e-mail]>
>To: Randy Bush <[e-mail]> 
>Cc: IPv6 Ops WG <[e-mail]>; Al Morton <[e-mail]> 
>Sent: Sunday, 1 September 2013 2:48 AM
>Subject: Re: [v6ops] draft-elkins-v6ops-ipv6-pdm-recommended-usage-00
> 
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>No question that there are lots of systems which do not have their clocks synchronized.  Indeed, a lot of PCs aren't even synchronized to the nearest 10 seconds, let alone anything finer.
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>But then, a lot of PCs aren't in need of synchronization.  Nobody (except maybe the individual user) is concerned about response time for them -- or going to consider doing anything about response times that aren't a matter of tens of minutes, and on an on-going basis.   
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>The issue is all of the systems where response times DO matter.  Those clocks do get synchronized already, because there is a need that justifies the effort required to do so.  The challenge then becomes, How do we measure transmission times between those systems once they convert to IPv6?  When there is no way in IPv6 to record those times, that is a problem.  
>

As far as I'm aware there is no way to record those times specifically in IPv4. So how is it being done now in IPv4, "before IPv6"?

I don't think the answer isn't NTP, because NTP runs over UDP, and therefore can and does run over both IPv4 and IPv6.

I don't think the answer is  PTP/IEEE 1588 because that's both a fairly recent development and is only single LAN rather than Internet scale.


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>And this isn't the only approach that is being considered -- just the only one (that I am aware of) which doesn't involve adding extra hardware at the end-points.  (Hardware which will also require some kind of clock synchronization.)
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> 
>Bill Jouris
>Inside Products, Inc.
>www.insidethestack.com
>831-659-8360
>925-855-9512 (direct)
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>
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>________________________________
> From: Randy Bush <[e-mail]>
>To: Nalini Elkins <[e-mail]> 
>Cc: IPv6 Ops WG <[e-mail]>; Al Morton <[e-mail]> 
>Sent: Saturday, August 31, 2013 6:01 AM
>Subject: Re: [v6ops] draft-elkins-v6ops-ipv6-pdm-recommended-usage-00
> 
>
>> If you are arguing that time synchronization cannot be done to the
>> millisecond or microsecond level
>
>not arguing.  just trying to explain to you that a lot of engineering
>and research have shown that ntp, pee cees running unix or linux with
>gps, ... do not have millisecond accuracy on stamping packets over the
>net.  folk are trying to save you wasted effort.  
>
>randy
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