On Feb 23, 2017, at 8:04 AM, Tim Bray <[email protected]> wrote: > To me, if a pool server is visible from half the internet, but not the > other half. Somebody puts pool.ntp.org into their computer with an SNTP > client. DNS gives them an inaccessible client. The time doesn't set. > Their conclusion is `The NTP pool is broken`
It strikes me that the monitoring system for the NTP pool is likely to have similar problems to NTP itself. If you have only one clock (monitor), then you absolutely know what time it is (if the site is up), even if you’re technically wrong. But, if you have two, then you have no idea what time it is (if the site is really up). So, I think you might have to implement the same kind of Byzantine agreement (2n+1) algorithm to properly monitor the NTP pool. And that’s just if you monitor all the servers in the pool as one big resource. If you want to partition that down by country or region of the world, then I’d think you would have to replicate that kind of infrastructure at the other levels, and ensure that each of those other 2n+1 monitors operates exclusively from within the zone they are claiming to monitor from/for. -- Brad Knowles <[email protected]>
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