nanog mailing list archives
Re: NTP question
From: Mel Beckman <mel () beckman org>
Date: Wed, 1 May 2019 23:53:48 +0000
Ask, But with a small compact server like the DC-powered TimeMachines Inc unit, which costs something like $300, you simply put the server where the visibility is and connect back to the nearest Ethernet port in your network, up to 300’ away, or virtually any distance with fiber transceivers. We’ve installed these in Cantex boxes on a windy, rainy tenth-story rooftop in upstate NY and it runs flawlessly, warmed by its own internal heat at sub-zero temps, and perfectly happy at ambient temps of 110F. It’s hard to consider messing with signal converters and pricey remotely-powered active antennas when you can solve the problem for $300. :) -mel
On May 1, 2019, at 4:44 PM, Ask Bjørn Hansen <ask () develooper com> wrote:On May 1, 2019, at 12:22, Mehmet Akcin <mehmet () akcin net> wrote: 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.[ with my hobby-hat on … ] tl;dr: if any of the below is too much work, just run reasonably well monitored NTP server syncing from other NTP servers. If you want more than that, you need to see the sky. Don’t do the CDMA thing. Depending on your requirements having the antenna in the window may or may not be satisfactory. If it’s fine you probably could just have done a regular NTP server in the first place. For long swaths of the day you might not see too many satellites which will add to the uncertainty of the signal. Meinberg’s GPS antenna has a bit more smarts which helps it work on up to 300 meters on RG58 or 700 meters on RG213. (They also have products that use regular L1 antennas with the limitations Bryan mentioned). https://www.meinbergglobal.com/english/products/gps-antenna-converter.htm They also have a multi-mode fiber box to have the antenna be up to 2km from the box or 20km with their single mode fiber box, if you have fiber to somewhere else where you can see the sky and place an antenna. It will be more than the one you linked to, but their systems are very reasonably priced, too. For “hundreds of customers” whatever is the smallest/cheapest box they have will work fine. Even their smallest models have decent oscillators (for keeping the ticks accurate between GPS signals). The Meinberg time server products (I am guessing all of them, but I’m not sure) also have a mode where they poll an upstream NTP server aggressively and then steer the oscillator after it. I haven’t used it in production, but it worked a lot better than it sounded like it would. (In other words, even without GPS it’s a better time server than most systems). Ask
Current thread:
- Re: NTP question, (continued)
- Re: NTP question Eric S. Raymond (May 06)
- Re: NTP question Mel Beckman (May 01)
- Re: NTP question Rubens Kuhl (May 01)
- Re: NTP question Alejandro Acosta (May 01)
- Re: NTP question Mike Hammett (May 01)
- Re: NTP question Brielle Bruns (May 01)
- Re: NTP question Carsten Bormann (May 01)
- Building Integrated Timing System (was Re: NTP question) Sean Donelan (May 02)
- Re: NTP question Eric S. Raymond (May 06)
- Re: NTP question Mike Hammett (May 01)
- Re: NTP question Ask Bjørn Hansen (May 01)
- Re: NTP question Mel Beckman (May 01)
- Re: NTP question Ask Bjørn Hansen (May 01)
- Re: NTP question Marco Davids via NANOG (May 02)
- Re: NTP question Harlan Stenn (May 01)
- Re: NTP question Mel Beckman (May 01)
- Re: NTP question Gary E. Miller (May 01)
- Re: NTP question Mel Beckman (May 01)
- Re: NTP question Gary E. Miller (May 01)
- Re: NTP question Mel Beckman (May 01)
- Re: NTP question Mel Beckman (May 01)
- Re: NTP question Mel Beckman (May 01)
- Re: NTP question Harlan Stenn (May 01)