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Re: Question on Loosely Synchronized Router Clocks

  • From: Deepak Jain
  • Date: Mon Sep 17 18:34:08 2007



[email protected] wrote:
On Mon, 17 Sep 2007 14:28:45 PDT, Kevin Oberman said: 
I had a router that lost it's NTP servers and was off by about 20
minutes. The only obvious problem was the timestamps in syslog. (That's
what alarmed to cause us to notice and fix it.)


Trying to correlate logfiles with more than a several-second offset is
good and sufficient reason in itself to make sure everything is NTP-synched.


So to bring the conversation to something more sequitur and relevant.

1) Its not hard <tm> to keep all of your devices in your network sync'd to the same clock. Especially if you use standardized configuration control.

2) And a reasonable number is on the order of seconds (or ~1 second) rather than minutes which is almost the same as being unsynch'd.

3) It is not guaranteed, but not hard to be sync'd to a level of precision on the order of a second or two using globally-available NTP sources to every other network you might directly connect with.

I'm slightly suspicious of all the CDMA/atomic clock other NTP sources (for "higher precision") people point their IP gear at -- simply because IP doesn't need the same level of precision as SONET, at least, not yet.

[exclusions for my suspicion include any NTP sources I run, but that's merely hubris ;)].

Deepak Jain