nanog mailing list archives
Re: NIST NTP servers
From: Lamar Owen <lowen () pari edu>
Date: Sat, 14 May 2016 10:27:41 -0400
On 05/13/2016 04:38 PM, Mel Beckman wrote:
While this is drifting a bit off-topic for NANOG (and drifting into the topic range for time-nuts () febo com), I'll just add one more thing to this. The Hold time (when the oscillator is free-running) is a very important consideration, especially, as you say, when terrain is an issue. For us it is even more important, as the 10MHz output from the timing rack is used as a site-wide frequency standard. Of course, you never discipline a cesium PRS, but the rubidium secondary is disciplined by circuitry in the SSU2000.But another key consideration beyond accuracy is the reliability of a server's GPS constellation view. If you can lose GPS sync for an hour or more (not uncommon in terrain-locked locations), the NTP time will go free-running and could drift quite a bit. You need an OCXO to minimize that drift to acceptable levels.
Back in the days of common backbone delivery over SONET discussion of cesium standards would have been on-topic, as some SONET gear (Nortel Optera for instance) needs a master clock; especially if you were delivering channelized circuits or interfacing with customers and telcos with DS3 or even DS1 circuits or DS0 fractions within them. Ethernet is far more forgiving.
Current thread:
- Re: NIST NTP servers, (continued)
- Re: NIST NTP servers Mel Beckman (May 12)
- Re: NIST NTP servers Leo Bicknell (May 11)
- Re: NIST NTP servers Brandon Vincent (May 11)
- Re: NIST NTP servers Jon Meek (May 11)
- Re: NIST NTP servers Josh Reynolds (May 11)
- Re: NIST NTP servers Lamar Owen (May 13)
- Re: NIST NTP servers Mel Beckman (May 13)
- Re: NIST NTP servers Lamar Owen (May 13)
- Re: NIST NTP servers Mel Beckman (May 13)
- Re: NIST NTP servers Mel Beckman (May 13)
- Re: NIST NTP servers Lamar Owen (May 14)
- Re: NIST NTP servers Laszlo Hanyecz (May 13)
- Re: NIST NTP servers Chuck Anderson (May 13)
- Re: NIST NTP servers Sharon Goldberg (May 13)
- RE: NIST NTP servers John Souvestre (May 12)
- Re: NIST NTP servers Chris Adams (May 12)
- RE: NIST NTP servers John Souvestre (May 12)
- RE: NIST NTP servers Chuck Church (May 11)
- Re: NIST NTP servers George Herbert (May 12)
- RE: NIST NTP servers Allan Liska (May 11)
- RE: NIST NTP servers Chuck Church (May 10)