[ntp:questions] ARRGH!!! I woke up to a 50 SECOND clock error.

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Wed Mar 14 21:04:33 UTC 2012

On 3/14/2012 4:00 PM, David J Taylor wrote:
>> Hi David T,
>> NOW .... you understand.
>> I have 4 PC's connected to the LAN, plus my wife's work computer 3 
>> days / week, and on rare occasions my son's computer.  All are 
>> connected by wifi.  All do pretty mundane things: web browser, email, 
>> sometimes downloading patches, sometimes doing online backup.  My 4 
>> are running NTPD.  3 run windows most of the time and dual boot into 
>> linux.  My 4th machine runs linux all the time.  When my wife is 
>> here, she does a remote desktop type of thing into her work system.  
>> Two of my PC's are running Vista, one is running Windows 7.  Those 
>> three dual boot into Ubuntu 11.04 and the always linux machine runs 
>> Ubuntu 11.04.  Almost all the discussions I've had on this mailing 
>> list are for my Windows 7 machine.
>> The path out of my house is:
>> PC Wifi --> Wifi router --> wired router --> cable modem --> ISP --  
>> internet
>>> - is this PC connected over wireless or wired?
>> Wifi G
>>> - what else is going through the router?  Someone else downloading 
>>> large files or using streaming audio or video?
>> See above.  Normally, no huge data hogs.
>>> - who else might be sharing your connection?
>> It's cable.  Who knows?  I also get cable TV and telephone through 
>> the same wire.
>>> - what type of service do you have?  Presumably not dial-up!  But 
>>> what speed?
>> Comcast Cable
>> Just tested it with speedtest.net
>>      Ping to near city: 91 ms, Download: 29.63 Mbps, Upload: 5.3 Mbps
>>> - having checked you speed, would you describe your connection as 
>>> "stable"?
>> See above for speed.  Generally, it's very stable.  However, for the 
>> purposes we're discussing, I think it's latencies and delays that are 
>> the problem.
>> As I mentioned in my reply to David L, I'm not concerned over trying 
>> to get stellar performance from internet servers.  I just want to get 
>> a good GPS server system running and use the internet servers as a 
>> backup.
>> Sincerely,
>> Ron
> Ron,
> Thanks for that clarification.  I think you should be getting /very 
> much/ better performance from your Internet servers.  That ping is 
> poor as well. Here I have 30 Mb/s down, just 1 Mb/s up, and NTP delays 
> show as 18-34 ms (most in 22-30 ms).
> To that end, if your cable modem has multiple ports, connect one of 
> the PCs direct to the CM and run it as your local NTP server.  Wi-Fi 
> doesn't help NTP.  Later, you can add GPS/PPS to that PC as well.  At 
> the very least, connect your timekeeping PC direct to the wired 
> router.  No Wi-Fi! For my main NTP server, I got a low-powered and 
> fan-less Intel Atom system, and it runs FreeBSD.  It /only/ runs NTP, 
> no interactive stuff at all.
> You might also consider getting rid of the two routers and just using 
> the wireless one.  You might also see whether you can run NTP on your 
> router - perhaps it's a model which can run the DD-WRT firmware.  I 
> think some variants of DD-WRT can run NTP, but please check.  I have a 
> WRT 54GL in my system where I run the DD-WRT firmware.
>  http://www.dd-wrt.com/site/index
> Online backup could well affect the performance of the connection for 
> timekeeping, and your imminent Sure GPS/PPS will help enormously.
> Just some thoughts which may help you along the way.
> Cheers,
> David

Hi David,

I really appreciate all these suggestions you shared, as well as past 
ones.  If I decide to revamp my network, I'll probably put some of them 
into use.  However, that's not really practical right now.  All the 
networking gear is in the basement and all the PC's are upstairs.  I've 
already spent 2 months working on this GPS stuff and ignoring some other 
things I need to be doing.  I think I'm just going to focus on getting 
the Sure board up and running on a time server when it comes and, 
perhaps, use my BU-353 as a backup time source, and use the internet 
servers as a third level backup source.  Most of the time, I won't care 
what they're doing  Hopefully, I can spend less time thinking about time 
and just know that my PC's clocks are right.  Regardless, I'm going to 
continue to have an interest in the topic and have enjoyed all the 
discussions and learning that have occurred.  It's just that I have to 
do at least a few other things besides this.




(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
such.  I don't always see new messages very quickly.  If you need a
reply and have not heard from me in 1 - 2 weeks, send your message again.)

Ron Frazier
timekeepingdude AT c3energy.com

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