Re: NTP accuracy?

Oliver Xymoron (oxymoron@waste.org)
Wed, 2 Dec 1998 13:55:10 -0600 (CST)

> On Tue, Dec 01, 1998 at 01:05:41PM -0800, Larry McVoy wrote:
> > excuse the ignorance of this question, but suppose you had 1,250
> > systems hooked up to a networking fabric with 10usec end-end propogation
> > times, but the times can vary depending upon contention. What I want to
> > know is this: how accurately can NTP sync the clocks across all those
> > machines? I know it may be asking for too much, but is it possible to
> > get 1usec accuracy? If it makes it any easier, this is a controlled
> > environment, so it is possible to have a tree structure in the nodes
> > such that the times fanout very quickly to all nodes.

Hmmm.. if these machines are only communicating via the network (that is,
they're not involved in controlling or observing a real world high speed
process), I'm not really sure what use can be made of accuracy better than
half of the minimum round trip time (approximately node to node latency).
If synchronization is within that window, then all communication will
appear to be causal, meaning every time stamp received or relayed through
the network will appear to be in the past for all routes.

--
 "Love the dolphins," she advised him. "Write by W.A.S.T.E.." 




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