Rui Ferreira wrote: > > I believe you are somewhat wrong, as the dns servers actually make > round-robin on a per request basis. > If you try "dig pool.ntp.org. @a.ntpns.org" several repeated times you will > see the round-robin working on a per request basis, that is, you will see the > returned ip's rotating on each request. > The problem that you are talking about is related to the TTL of the results, > 2700 sec at this moment, that is, the result will remain in dns cache for > 2700 sec. > No. The problem is that the DNS returns 14 addresses from the pool for each domain name within the pool (e.g. pool.ntp.org, europe.pool.ntp.org, nl.pool.ntp.org) even when that part of the pool has many more than 14 servers. The set of 14 servers remains the same for one hour, only the sequence within this set of 14 rotates. So, when there are 500 servers in the pool and a large group of users tries to get time using simple NTP (a single request to retrieve the current time), all the requests from that large group of users go to only 14 out of the 500 servers. The servers in that group of 14 see a "spike", and the remaining 486 servers have nothing to complain about.
An hour later, 14 different servers see a "spike". That is why I claim this spike is not caused by Türk Telecom but by our DNS system. When the DNS would really rotate over all 500 servers, the load would be distributed over 500 instead of 14 servers and the spike would be 35 times lower. Of course there is the problem that DNS typically uses caching servers and so you cannot rotate as fast as you would like. Rob _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
