nanog mailing list archives
Re: Cost-effectivenesss of highly-accurate clocks for NTP
From: Mel Beckman <mel () beckman org>
Date: Sat, 14 May 2016 19:42:13 +0000
I clearly need three of those maser things for my network.
Gives new meaning to the phrase "Set and forget". :) -mel beckman
On May 14, 2016, at 12:40 PM, Baldur Norddahl <baldur.norddahl () gmail com> wrote:On 13 May 2016 at 23:01, Baldur Norddahl <baldur.norddahl () gmail com> wrote: Ok how many hours or days of holdover can you expect from quartz, temperature compensated quartz or Rubidium? Should we calculate holdover as time until drift is more than 1 millisecond, 10 ms or more for NTP applications? I am thinking that many available datacenter locations will have poor GPS signal so we can expect signal loss to be common. Some weather patterns might even cause extended GPS signal loss.I found some data points here: https://en.wikipedia.org/wiki/Crystal_oven Assuming that acceptable drift is 10 milliseconds due that being the expected accuracy from NTP. The common crystal oscillator can be as bad as 1E-4 => holdover time is 2 minutes. TCXO is listed as 1E-6 => holdover time is 3 hours. OCXO is listed as multiple values, I will use 1E-7 => holdover time is 1 day. Rubidium is listed as 1E-9 => 3 months Caesium is listed as 1E-11 => 30 years Hydrogen Maser 1E-15 => 300 millennia I clearly need three of those maser things for my network. Regards, Baldur
Current thread:
- Cost-effectivenesss of highly-accurate clocks for NTP Eric S. Raymond (May 13)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Baldur Norddahl (May 13)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Baldur Norddahl (May 14)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Mel Beckman (May 14)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Eric S. Raymond (May 15)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Mel Beckman (May 15)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Eric S. Raymond (May 15)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP joel jaeggli (May 15)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Mel Beckman (May 15)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Lamar Owen (May 16)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Mel Beckman (May 16)
- RE: Cost-effectivenesss of highly-accurate clocks for NTP Jameson, Daniel (May 16)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Baldur Norddahl (May 14)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Baldur Norddahl (May 13)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Valdis . Kletnieks (May 15)
- Re: Cost-effectivenesss of highly-accurate clocks for NTP Måns Nilsson (May 15)