On Tue, Oct 7, 2008 at 2:57 PM, Jeff <[EMAIL PROTECTED]> wrote: > I don't see the fascination with location here. I don't care if ntp > servers that I sync with are next door or around the world, as long as > they're reliable, and consistently accessible. > > Sure, the physical proximity of a server may be a good place to start, > but it's far from the answer.
Geographic location is important as it has a fairly strong correlation with "network location". You want NTP servers that are close network-wise for several reasons: 1) Accuracy - low latency means lower error bounds 2) Predictable routing - Almost no internet path of mroe than a few hops is symmetric. This behavior is almost guaranteed by BGP and the "cold-potato" routing scheme used by all major ISPs. The NTP protocol assumes symmetric network paths, but that is a bad assumption on the Internet, unless the servers are very close in the network sense. 3) Jitter - every time a packet crosses a router, non-deterministic delay is added by the router's queuing mechanisms and current traffic load. More routers = more jitter. 4) Bandwidth - the pool already serves millions of clients, and anything that can be done to localize the pool's traffic is good for scalability and the internet as a whole. It would be ideal to have a system that could predict network location well without worrying about geography, but that is not an easy problem to solve (see myh other recent post). -- RPM _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
