nanog mailing list archives
Re: NTP Issues Today
From: Leo Bicknell <bicknell () ufp org>
Date: Tue, 20 Nov 2012 11:00:11 -0800
After some private replies, I'm going to reply to my own post with some information here. It appears many people don't understand how the NTP protocol works. I suspect many people have configured a "primary" and a "backup" NTP server on many of their devices. It turns out this is the _WORST_ possible configuration if you want accurate time: http://support.ntp.org/bin/view/Support/SelectingOffsiteNTPServers#Section_5.3.3. To protect against two falseticking servers (tick and tock, as we saw on the 19th) you need _FIVE_ servers minimum configured if they are both in the list. More importantly, if you want to protect against a source (GPS, CDMA, IRIG, WWIV, ACTS, etc) false ticking, you need a minimum of _FOUR_ different source technologies in the list as well. It's not hard, my box that I posted the logs from peers with 18 servers using 8 source technologies, all freely available on the Internet... -- Leo Bicknell - bicknell () ufp org - CCIE 3440 PGP keys at http://www.ufp.org/~bicknell/
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Current thread:
- RE: NTP Issues Today, (continued)
- RE: NTP Issues Today Wallace Keith (Nov 19)
- Re: NTP Issues Today George Herbert (Nov 19)
- Re: NTP Issues Today Sid Rao (Nov 20)
- Re: [outages] NTP Issues Today Mike Lyon (Nov 19)
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- Re: [outages] NTP Issues Today Colin Johnston (Nov 20)
- Message not available
- Re: [outages] NTP Issues Today Colin Johnston (Nov 20)
- RE: NTP Issues Today Wallace Keith (Nov 19)
- Message not available
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- RE: [outages] NTP Issues Today R. Benjamin Kessler (Nov 20)
- Re: NTP Issues Today Seth Mattinen (Nov 20)
- Re: NTP Issues Today Steve Meuse (Nov 20)
- Re: NTP Issues Today Leo Bicknell (Nov 20)
- Re: NTP Issues Today Jay Ashworth (Nov 20)
- Re: NTP Issues Today Jared Mauch (Nov 20)
- Re: NTP Issues Today George Herbert (Nov 20)
- Re: NTP Issues Today Leo Bicknell (Nov 20)
- Re: NTP Issues Today Darius Jahandarie (Nov 20)
- Re: NTP Issues Today Mike Lyon (Nov 20)
- Re: NTP Issues Today Jared Mauch (Nov 20)
- Picking outside NTP servers (Re: NTP Issues Today) Jay Ashworth (Nov 20)
- Re: Picking outside NTP servers (Re: NTP Issues Today) George Herbert (Nov 20)
- Re: Picking outside NTP servers (Re: NTP Issues Today) Majdi S. Abbas (Nov 20)