nanog mailing list archives
Re: NTP question
From: Mike Hammett <nanog () ics-il net>
Date: Wed, 1 May 2019 21:06:31 -0500 (CDT)
What about GPS, GLONASS, Galileo, etc.? ----- Mike Hammett Intelligent Computing Solutions http://www.ics-il.com Midwest-IX http://www.midwest-ix.com ----- Original Message ----- From: "James R Cutler" <james.cutler () consultant com> To: "Harlan Stenn" <stenn () nwtime org> Cc: nanog () nanog org Sent: Wednesday, May 1, 2019 8:55:51 PM Subject: Re: NTP question On May 1, 2019, at 9:45 PM, Harlan Stenn < stenn () nwtime org > wrote: On 5/1/19 5:39 PM, William Herrin wrote: <blockquote> On Wed, May 1, 2019 at 12:23 PM Mehmet Akcin < mehmet () akcin net > wrote: <blockquote> I am trying to buy a GPS based NTP server like this one https://timemachinescorp.com/product/gps-time-server-tm1000a/ but I will be placing this inside a data center, do these need an actual view of a sky to be able to get signal or will they work fine inside a data center building? if you have any other hardware requirements to be able to provide stable time service for hundreds of customers, please let me know. You buy a powered GPS antenna for it. Which antenna depends on the cable length and type. The amplifier in the antenna amplifies the signal just enough to overcome the cable loss between the antenna and the receiver. Nice thick cables lose less signal. Dinky thin ones are easier to work with. You sure you need a GPS NTP server? You understand that if you do, you need two for reliability right, and probably at geographically diverse locations? If you're not on an air-gapped network, consider syncing a couple head-end NTP servers against tick and tock (.usno.navy.mil, the naval observatory) and not worrying about it. One less piece of equipment to manage, update, secure, etc. </blockquote> Two is not a great number. If they disagree, there is no majority clique to be found. Also, there is something to be said for using different models/vendors for the time sources. If you only have the same model from one vendor and there is a bug, you can lose all your time sources at once. The GPS week rollover happens every ~19.7 years, and when that problem hits is a function of the firmware and a manufacturing date put in the firmware. These problems can be mitigated if you have "enough" time sources for your internal NTP servers and you peer with enough other, possibly your, servers. <blockquote> Regards, Bill Herrin </blockquote> -- Harlan Stenn < stenn () nwtime org > http://networktimefoundation.org - be a member! </blockquote> To amplify the points made by Harlan Stenn: Four is a better number locally for ntpd instances. As for different models/vendors for the time sources, I consider the GPS constellation as one vendor so I add multiple internet-connected sources as well to my ntp.conf instances. James R. Cutler James.cutler () consultant com GPG keys: hkps://hkps.pool.sks-keyservers.net <blockquote> </blockquote>
Current thread:
- Re: NTP question, (continued)
- Re: NTP question Mel Beckman (May 02)
- Re: NTP question Seth Mattinen (May 03)
- Re: NTP question william manning (May 03)
- Re: NTP question Eric S. Raymond (May 06)
- Re: NTP question Keith Wallace (May 01)
- Re: NTP question Valdis Klētnieks (May 01)
- Re: NTP question William Herrin (May 01)
- Re: NTP question Chris Adams (May 01)
- Re: NTP question Harlan Stenn (May 01)
- Re: NTP question James R Cutler (May 01)
- Re: NTP question Mike Hammett (May 01)
- Re: NTP Question Mel Beckman (May 01)
- Re: NTP Question Harlan Stenn (May 01)
- Re: NTP question Mel Beckman (May 02)
- Re: NTP question Ge DUPIN (May 02)