Hi, I just noticed that there are some NTP servers in the pool which are serving in all regions and which are obviously anycasted [1]. For example this server, provided by NTT communications: -> http://www.pool.ntp.org/scores/129.250.35.251
It's just 0.5 ms away from the LAX monitoring server and for me (near Duesseldorf) about 5ms away located in Frankfurt. That is pretty good to have an anycasted NTP server which is available to nearly all networks with very low fault rates. But: You can't monitor those servers with only one monitoring station hosted on one network. That's where you have to do a more complex monitoring. I guess, NTT is observing it's own NTP server good enough to ensure it's reachable and serving stable time - but the NTP pool's monitor system is unable to notice if the anycast instance in Frankfurt servces a wrong time because it can only reach the instance running in Los Angeles. And as long as this one instance is up and working the monitor won't kick it out of the pool, at least for the "bad" region. I understand that anycasted servers might be a very small minority in the pool and thus, it might be OK to shift the responsibility for monitoring to the providers of these servers. It's just an example for situations where you can't monitor with just one monitoring system. [1] https://en.wikipedia.org/wiki/Anycast Greetings Max Am 23.02.2017 um 22:25 schrieb Arnold Schekkerman: > Usually it is not the transatlantic link link, but the (temporary) filtering > policies of a network company that operates at both sides of the transatlantic > link. I remember a situation in the UK, where one system with upstream to > company A > could not connect to an NTP server with upstream company B. Situations where > both > client and server were routed through upstream A only worked fine. The same > was > true for client servers via upstream B only. > > Networks do not follow the borders of the country (in most countries...)
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