On 2011-12-27, Danny Mayer <[email protected]> wrote: > On 12/26/2011 11:17 PM, ben slimup wrote: >> Thanks Danny for your reply, >> >> but is it a big problem, if the client round-trip packet comes from a >> different servers each time? why? >> > > Because NTP uses multiple packets to gain data on the round-trip delay, > jitter, etc. of each server it gets responses from. The round-trip delay
No it doesn't. It uses one outbound and one inbound packet to get the delay time. Ie, one packet arrives at the server, and one exits the server. Now if you are talking about statistics, that is different, and using many will increase the jitter. If the two machines are "good" then their times should agree within the jitter anyway. > is different if it comes from different systems. In addition each system > has its own idea of what the correct time is and at the point that it > receives and sends out the reply packet. The resulting data points will Not if they are all synchronised to UTC. > be so uneven if it's coming from the different systems that it will > never select that system as accurate and will almost certainly remove it > from the list of possible candidates. The data for each specific IP ??? > address is collected this way and compared to data from other IP > addresses. Load-balancing breaks that since it's really a different > system that it can get data from. Instead of load balancing you give > each system its own IP address and it can synchronize against those systems. I agree that it is not a good idea, but it is not a disasterous idea assuming your servers are "good" servers. > > Danny >> thank you again >> >>> Date: Mon, 26 Dec 2011 22:39:22 -0500 >>> From: [email protected] >>> To: "terje.mathisen at tmsw.no"@ntp.org >>> CC: [email protected] >>> Subject: Re: [ntp:questions] ntp server pool advice >>> >>> On 12/22/2011 6:40 AM, Terje Mathisen wrote: >>> > ben slimup wrote: >>> >> >>> >> Dear all, >>> >> >>> >> Thank you very much for support, >>> >> >>> >> i do not have 1000,000 client, i need those ntp servers to serve a >>> >> load between 100000 to 1000000 clients >>> >> over a public network with an accuracy of 100ms >>> >> >>> >> those clients will use dns round robin to resolve 4 external ip, 2 IPs >>> >> on each site. >>> > >>> > DO NOT USE ROUND ROBIN DNS for NTP! >>> >>> You can use round robin dns for NTP. There's nothing wrong with that. >>> It's load balancing that must NOT be used as you would get different >>> answers from different systems each time. >>> >>> Danny >>> _______________________________________________ >>> questions mailing list >>> [email protected] >>> http://lists.ntp.org/listinfo/questions _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
