[ntp:questions] frequency adjusting only

David L. Mills mills at udel.edu
Fri May 2 18:07:22 UTC 2008


Greg,

Times change, no pun. Once upon a time an autocorellation function of 
Internet delays showed significant peaks corresponding to daylight 
working hours, complete with lunchtime lulls. That was when packets 
lived most of their lives on queues; now they live mostl on 
overprovisioned fiber or in space. LRD effects were than and now largely 
believed to be due to the length of TCP connections.

Dave

Greg Dowd wrote:

> At a guess, it's the correlation that had a period of 2 wks.  I'd guess
> it as a harmonic of a week somehow.  But who knows.  That's the problem
> with lrd.
> 
>   
> Greg Dowd
> gdowd at symmetricom dot com (antispam format)
> Symmetricom, Inc.
> www.symmetricom.com
> "Everything should be made as simple as possible, but no simpler" Albert
> Einstein
>  
> 
> 
>>-----Original Message-----
>>From: questions-bounces+gdowd=symmetricom.com at lists.ntp.org 
>>[mailto:questions-bounces+gdowd=symmetricom.com at lists.ntp.org]
>> On Behalf Of Brian Utterback
>>Sent: Friday, May 02, 2008 7:38 AM
>>To: questions at lists.ntp.org
>>Subject: Re: [ntp:questions] frequency adjusting only
>>
>>David L. Mills wrote:
>>
>>
>>>Suspecting such could be the case between NTP servers and 
>>
>>clients, I 
>>
>>>designed an experiment to detect such things and found small but 
>>>significant LRD effects with lags up to TWO WEEKS! At short 
>>
>>lags up to 
>>
>>>several network turns this can be explained by packet lengths, 
>>>buffering, retransmissions, etc., but at much longer lags 
>>
>>you have to 
>>
>>>look for routing flaps, provisioning changes, etc.
>>>
>>
>>Dave, are you saying that you saw an instance of a NTP 
>>response arriving 2 weeks after the request was sent?
>>
>>Brian Utterback
>>
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>>questions mailing list
>>questions at lists.ntp.org
>>https://lists.ntp.org/mailman/listinfo/questions
>>




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