Re: Question on Loosely Synchronized Router Clocks

[bmanning () vacation karoshi com]

 top posting to keep you alert!

 there are folks who syncronize clocks so that logs make sense.
 and those that do, tend to pick a common TZ...  there is nothing
 like syncronizing logs from routers in Nepal, India, China, and LA
 UTC can be your friend...  

 wrt acces to clock source - i'd be happy to have the httpd server 
 code pulled out and adding a GPS/802.11 timesource to the platform
 of joy.  of course presuming that a router clock is ammenable to 
 an external discipline source.  Many PC's are not...

--bill


On Tue, Sep 18, 2007 at 02:40:16PM -0500, Stephen Sprunk wrote:
> Thus spake "Xin Liu" <smilerliu () gmail com>
> > Sorry for the confusion. Let me clarify.
> >
> > We are interested in a number of questions:
> > 1. Can we assume loosely synchronized router clocks in the
> > Internet, or we have to make absolutely no assumption about
> > router clocks at all?
>
> That assumption is _generally_ true, but not often enough that you can rely 
> on it.
>
> > 2. If the router clocks are indeed loosely synchronized, what is
> > the granularity we can assume? Particularly, we are interested in
> > whether we can assume router clocks are synchronized within
> > 10 minutes.
>
> My experience is they'll either be within a few seconds or off by several 
> days to years.  There's not much middle ground.
>
> > 3. It's always possible that a router's clock goes wrong. In
> > practice, how often does this happen?
>
> It's unlikely to "go wrong" to any noticeable degree _if it was ever 
> correct in the first place_.  However, many people do not bother setting 
> the clocks at all (which will often result in a clock that's off by a 
> decade or more), or intentionally set them to be wrong.  A lot of folks had 
> to set their clocks back a few years around Y2k, for instance.
>
> S
>
> Stephen Sprunk         "God does not play dice."  --Albert Einstein
> CCIE #3723         "God is an inveterate gambler, and He throws the
> K5SSS        dice at every possible opportunity." --Stephen Hawking