nanog mailing list archives
Re: ntp config tech note
From: Michael Sinatra <michael () rancid berkeley edu>
Date: Thu, 20 May 2004 21:16:41 -0700
Robert E. Seastrom wrote:
"Hannigan, Martin" <hannigan () verisign com> writes:That's NTPv4 isn't it?I also prefer to use three peers vs. two. Always an odd number,greater than 1. Assumptions can't be made about the mathematics behind time, but in a reference model, odd numbers are better.Actually, three is not enough; Mills says at least four. Diversity in manufacturer (and controlling organization if you can spare the cycles) is a big big plus. You may wish to read Dr. Mills' post to comp.protocols.time.ntp in the wake of the TrueTime bug of the 2001->2002 new year: http://groups.google.com/groups?hl=en&selm=3C32924F.994E1D01%40udel.edu
If you're really paranoid, diversity in reference sources should also be considered. You should have more than one stratum-1, and as a group they should get time from more than one of [GPS, WWV/WWVB/DCF77/CHU/JJY/ETC., USNO, ACTS, etc.] and your stratum>1s should get time from multiple stratum-1s of similarly diverse references.
Many NTP folk look down their nose at the radio sources, since GPS is more accurate. But if you already have a GPS stratum-1, then perhaps your next stratum-1 should be WWVB and friends, or you should have a backup assocation with someone who does. And remember that CDMA gets its time from GPS, so it doesn't "count" as a diverse source. Like I said, if you're really paranoid...
michael
Current thread:
- Re: ntp config tech note, (continued)
- Re: ntp config tech note Kevin Oberman (May 20)
- Re: ntp config tech note Joel Jaeggli (May 20)
- ntpd config tech note redux Randy Bush (May 20)
- Re: ntpd config tech note redux Steven M. Bellovin (May 20)
- Re: ntpd config tech note redux Petri Helenius (May 20)
- Re: ntpd config tech note redux Suresh Ramasubramanian (May 20)
- Re: ntpd config tech note redux Petri Helenius (May 20)
- Re: ntpd config tech note redux Steven M. Bellovin (May 20)
- Re: ntp config tech note Robert E. Seastrom (May 20)
- Re: ntp config tech note Michael Sinatra (May 20)