[ntp:questions] pruning the pool?

Danny Mayer mayer at ntp.org
Mon Jul 19 21:20:59 UTC 2010


On 7/18/2010 7:00 PM, Danny Mayer wrote:
> On 7/15/2010 6:37 PM, E-Mail Sent to this address will be added to the
> BlackLists wrote:
>> Rob wrote:
>>> hymie! wrote:
>>>> My servers are configured to use
>>>> server 0.us.pool.ntp.org
>>>> server 1.us.pool.ntp.org
>>>> server 2.us.pool.ntp.org
>>>> server 3.us.pool.ntp.org
>>>>
>>>> Through what I presume is a fluke of the DNS randomization, three of
>>>> my four hosts were:
>>>>  153.16.4.139 .INIT. 16 u 390 512 0 0.000 0.000 4000.00
>>>>  153.16.4.133 .INIT. 16 u 378 512 0 0.000 0.000 4000.00
>>>>  153.16.4.140 .INIT. 16 u 384 512 0 0.000 0.000 4000.00
>>>>
>>>> I tried searching the NTP web sites to figure out who
>>>>   maintains the NTP pools, and this was the best lead I got.
>>>>  If these hosts are no longer offerring NTP, can they
>>>>  (and perhaps others in that same net block) be removed
>>>>  from the pool?
>>
>> Pool servers are babysat and removed automatically.
>>  <http://www.pool.ntp.org/en/scores>
>>
>>> Hosts that are not offering NTP are automatically removed from the pool.
>>> Unfortunately, with (commonly used versions of) ntpd this DNS lookup
>>> is only done when it is started.  So when you get 4 working NTP servers,
>>> it may well happen that they stop offering NTP service later and you get
>>> the above result.
>>> It can be fixed by restarting ntpd.
>>
>> Isn't this greatly improved in NTP 4.2.7p22 and later?
>>  {When using the pool server option}
>>
>> Aren't the pool servers tossed after 10 polls without
>>  surviving clock selection and then NTP will get IPs for
>>  more pool servers?
>>
> 
> Not yet. That work is under way but it takes a lot of infrastructure
> work to do that.

A discussion with Dave Hart indicates that in p22 and later for the pool
only the it works like a manycastclient and adds and removes servers
using the IP addresses that it received. I don't know if it refetches a
new DNS list but that's certainly on my agenda.

Danny

> Danny
> 
>> e.g.
>>
>> tos minclock 6 minsane 4 cohort 1
>>
>> peer   myNTPserverClock.example.org iburst
>> server myNTPserverDyn.example.org iburst preempt
>> server myISPsNTPserver1.example.com iburst
>> server myISPsNTPserver2.example.com iburst
>> server myUpStreamsNTPserverA.example.net iburst
>> server myUpStreamsNTPserverB.example.net iburst
>>
>> pool   0.us.pool.ntp.org iburst
>> pool   1.us.pool.ntp.org iburst
>> pool   2.us.pool.ntp.org iburst
>> pool   3.us.pool.ntp.org iburst
>>
> 
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