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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Question on Loosely Synchronized Router Clocks
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" <[email protected]> > >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 >
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