[ntp:questions] Random Observation

Charles Elliott elliott.ch at comcast.net
Sun Jun 25 18:10:20 UTC 2017


FWIIW, on my machine and with the servers I use, IPv6 has longer and more
variable transit times than does IPv4, although the ISP (Comcast) and modem
are native IPv6.  This leads to slightly higher offsets and jitters with
IPv6 connections versus IPV4.  I tested the connections with ping, and the
transit time differences and their deviations are real.  Consequently,
generally I prefer to use IPv4 for NTP.  

It is pure speculation, but because IPv4 is much older that IPv6, the
carriers may have more experience optimizing the equipment, routes, and
connections with IPv4.

Caveat emptor: Unsolicited comments are often worth exactly what you pay for
them.  Do your own testing.

Charles Elliott

-----Original Message-----
From: questions
[mailto:questions-bounces+elliott.ch=comcast.net at lists.ntp.org] On Behalf Of
Richard Thomas
Sent: Sunday, June 25, 2017 5:58 AM
To: questions
Cc: Bob McDonald
Subject: Re: [ntp:questions] Random Observation

Hi Bob,

It appears that you are right.  Observe that "us.pool.ntp.org" just gives
IPv4 addresses - the same 4 addresses in random order.
I presume that the particular set of 4 addresses will be a slowly varying
function of time: wait an hour and you'll get a different group of 4.
though I haven't done that experiment.

But "2.us.pool.ntp.org" gives 4 IPv4 addresses and 4 IPv6 addresses.

I assume it's a deliberate choice, but I have no idea what the reasoning
behind it might be.

> almini:~ rbthomas$ host us.pool.ntp.org us.pool.ntp.org has address 
> 154.16.245.246 us.pool.ntp.org has address 209.133.217.165 
> us.pool.ntp.org has address 50.112.150.45 us.pool.ntp.org has address 
> 71.248.190.29

> almini:~ rbthomas$ host us.pool.ntp.org us.pool.ntp.org has address 
> 71.248.190.29 us.pool.ntp.org has address 50.112.150.45 
> us.pool.ntp.org has address 209.133.217.165 us.pool.ntp.org has 
> address 154.16.245.246

> almini:~ rbthomas$ host 2.us.pool.ntp.org 2.us.pool.ntp.org has 
> address 104.131.53.252 2.us.pool.ntp.org has address 204.2.134.162 
> 2.us.pool.ntp.org has address 142.4.196.99 2.us.pool.ntp.org has 
> address 66.135.44.92 2.us.pool.ntp.org has IPv6 address 
> 2600:3c00::f03c:91ff:fe91:5dd8 2.us.pool.ntp.org has IPv6 address 
> 2604:a880:800:10::1:9001 2.us.pool.ntp.org has IPv6 address 
> 2001:470:0:2c8::2 2.us.pool.ntp.org has IPv6 address 
> 2607:fcd0:100:c21::1f2a:e81b almini:~ rbthomas$
> 

Enjoy!
Rick

On Jun 22, 2017, at 7:33 AM, Bob McDonald <bmcdonaldjr at gmail.com> wrote:

> It seems as though when I use a config similar to the following I get 
> no
> IPv6 servers in my pool selections.
> 
> pool us.pool.ntp.org iburst
> pool north-america.pool.ntp.org iburst pool pool.ntp.org iburst
> 
> only when I add a number prefix (as below) to the entries do I get 
> IPv6 servers in my candidate list.
> 
> pool 2.us.pool.ntp.org iburst
> pool 2.north-america.pool.ntp.org iburst pool 2.pool.ntp.org iburst
> 
> Do I just not understand what *should* be configured?
> 
> Regards,
> 
> Bob
> _______________________________________________
> questions mailing list
> questions at lists.ntp.org
> http://lists.ntp.org/listinfo/questions

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