----- Original Message ----- From: "Rob Janssen" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Monday, August 06, 2007 7:51 PM Subject: Re: [time] What is happening here?
Chuck Swiger wrote: > Please note that they are NOT the cause of the spikes. Our DNS system is. > We send the same reply to one hour of requests from their routers, and > this causes all their traffic to be sent to a small subset of our clients. > That is our own fault, not theirs! > We should operate a more advanced DNS server that rotates the replies on > a per-request basis, not once per hour. Then there will be no spiking > as seen now. 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. So what is the problem of reducing the TTL of the records to something less, maybe 10 sec or even less? The problem is that it will result in a high load to the only 5 dns servers at this moment serving the whole pool, as all pool clients would contact the dns servers much much more frequently. But as all internet users generally use the cache dns servers of their ISP, would that increase the load to unacceptale values if the TTL was set to about 20 sec? Yes, ISP's have internal dns servers for their clients, so why not ntp servers too? The fact is that they may have already, but their clients are not aware of that. Generaly the dns configuration of the internet users is made using an automatic configuration protocol like DHCP, so users dont even have to know about dns configuration or even what the word dns means. The good news is that ntp servers can also be taken automatically from DHCP, the problem is that many if not all ntp clients dont even try to learn the ntp servers from DHCP. Just few months ago (just after I started playing with ntp and joined the pool) I noticed that my ISP had ntp servers configured already and announced via DHCP. Rui _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
