[ntp:questions] ntp server pool advice

Terje Mathisen "terje.mathisen at tmsw.no" at ntp.org
Thu Dec 22 18:09:07 UTC 2011


ben slimup wrote:
>
>
> Hi Terje,
>
> if i do not use nat how can i route private adresse to internet ?, i
> do not want to use ipv6.

What is your setup?

Are you an ISP, or do you have some control over the client configuration?

Assuming you are using private addresses for all your clients, by far
the simplest setup would be to setup your 4-6 private NTP servers in the
same private address range, and keep all communication private.

If I were you I would allow your internal servers to use multiple
external (pool.ntp.org?) as backup for your GPS sources.
>
> 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?

Proper NTP (i.e. if you control the clients!) is to use multiple (at 
least 4!) servers from each client.

If you just have to publicize an official server list, then I would use 
the same setup as the ntp pool, i.e. ntp.yourdomain.com would return 
multiple addresses, probably in random or round robin order.

We need more detail to help you!

Terje
>
> 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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-- 
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"



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