[ntp:questions] ntp server pool advice

ben slimup slimup78 at hotmail.com
Thu Dec 22 14:24:31 UTC 2011



Hi Terje,

if i do not use nat how can i route private adresse to internet ?, i do not want to use ipv6.

also i m planning to 2 boxes with 3 card on each site, how can i load balance between site if i m do not use round robin?

Thank for your support


> From: "terje.mathisen at tmsw.no"@ntp.org
> To: questions at lists.ntp.org
> Date: Thu, 22 Dec 2011 12:44:07 +0100
> Subject: Re: [ntp:questions] ntp server pool advice
> 
> ben slimup wrote:
> >
> > Thank for prompt answer Chris,
> >
> > Unfortunately, this ntp network should give time to specific clients
> > devices and not anyone on the public network.
> >
> > according to your advice, better not using load balancer, thats good
> > how to load balance between ntp server if i do not use round robin?
> > if all client choosing the same server then the ntp server will be
> > overload. is it a problem if for example client 1  poll or synch with
> > server 1 , and then with server 2 , etc...? or udp roundtrip comes
> > each time from different ntp server? how many ntp servers should be
> > needed to handle that much request knowing that each card handle
> > 10,000 request per sec?
> 
> First, each client should have at least 4 configured servers, so you can 
> use the same ntp.conf file for all of them.
> 
> Second, if you really can handle 10K requests/second per card, then that 
> means that you can handle 640K clients per card, with worst-case polling.
> 
> I.e. servers capable of 10K/second should handle your expected load just 
> fine, even though a proper (FreeBSD-based) 1U server with a GPS will 
> serve even more clients with better time performance.
> 
> Terje
> >
> > much appreciate your expertize
> >
> > cheers
> >
> >> From: albertson.chris at gmail.com Date: Wed, 21 Dec 2011 19:43:53
> >> -0800 Subject: Re: [ntp:questions] ntp server pool advice To:
> >> slimup78 at hotmail.com
> >>
> >> On Wed, Dec 21, 2011 at 5:07 PM, ben slimup<slimup78 at hotmail.com>
> >> 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. i have 4 servers with 4 ntp server slot card
> >>> each ( meinberg M900) 1 ntp server card can support 10,000
> >>> request.
> >>
> >> First off the good news.  100ms is an "easy" spec to meet you can
> >> do this without a lot of effort.
> >>
> >> Don't let the outside world "see" your meinberg servers.    Build
> >> out a layer of "statum 2" servers and expose those to your clients.
> >> 1M clients is a lot for the little 386 class CPU that is in the
> >> meinberg box.
> >>
> >> I still don't understand, Why do all those NTP clients need to go
> >> to your NTP servers. Why can't they use any they like?    Are your
> >> servers doing something special?
> >>
> >> Also know that EACH client needs to be configured to see multiple
> >> NTP servers.  practically three servers is a minimum but others
> >> will argue for more for five
> >>
> >> A would not use load balancing for NTP servers.    With NTP it
> >> does not matter at all if a server crashes.  The clients are all
> >> configure to use five servers and if one crashes they will do fine
> >> using four. If you expose four, large robust servers one on each of
> >> your four IP addresses then you will be fine, even if one fails you
> >> will be fine. The clients will notice the failure and continue on
> >> using the remaining three.
> >>
> >>
> >> I technical question for the list:  Would Round Robin load
> >> balancing even work.  I think it would introduce so much jitter the
> >> server would be  usless.  I think you have to be sure that each
> >> time a client pools a server at a given IP address it polls the
> >> same physical server.
> >>
> >> Chris Albertson Redondo Beach, California
> 
> 
> -- 
> - <Terje.Mathisen at tmsw.no>
> "almost all programming can be viewed as an exercise in caching"
> 
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