Does anyone here on the list know much about other systems that serve
the same purpose as pool.ntp.org? Apple runs time.apple.com. Does
Microsoft run anything for Windows clients, or will they? pool.ntp.org
is effectively the service for Debian; any other big Unix
distributions have an NTP service defaulting for them?
I'm curious what we can learn from these other services. I took a look
at time.apple.com. It's interesting.
My American MacOS 10.3.9 box has the following /private/etc/ntp.conf:
server time.apple.com minpoll 12 maxpoll 17
Interesting minpoll/maxpoll, that means polling somewhere between once
an hour and once every day and a half. I guess they chose to trade off
accuracy for scalability.
time.apple.com currently resolves to 4 IP addresses, 17.254.0.26, .27,
.28, and .31. All of them seem to be in San Jose, California. About
20ms away from my machine in San Francisco, about 200ms from Zurich.
.26 is currently stratum 2, the rest are stratum 3.
Their implementation seems to support the standard ntpdc requests, but
not monlist. I took a look at their peer lists and .26 and .27 both
have many peers. .28 and .31 seem to slave to just .26 and .27
respectively, presumably a load management thing?
.26 and .27 have identical peers, an interesting set. It includes
several stratum 1 clocks. They seem to have maxpoll set at 128
seconds, aggressive but maybe appropriate for such a well-used clock.
Some of their peers have evocative names like time2.euro.apple.com and
TrueTime.asia.apple.com. I wonder if Mac laptops set up for non-US
regions use different time servers?
Here's the .26 peer list:
$ ntpdc -n 17.254.0.26
ntpdc> peers
***Warning changing to older implementation
remote local st poll reach delay offset disp
=======================================================================
+17.254.1.193 17.254.1.70 3 128 377 0.00018 0.000318 0.00186
+17.254.1.194 17.254.1.70 3 128 377 0.00015 0.000313 0.00186
+17.254.1.71 17.254.1.70 2 128 375 0.00021 0.000145 0.00272
*17.106.100.13 17.254.1.70 1 128 377 0.01312 -0.000132 0.00381
=17.82.254.14 17.254.1.70 1 128 377 0.19658 0.004031 0.00380
=17.254.0.49 17.254.1.70 1 128 377 0.00471 -0.000837 0.00381
=17.72.133.55 17.254.1.70 1 128 377 0.16991 0.000789 0.00380
=17.72.133.54 17.254.1.70 1 128 377 0.17471 -0.000790 0.00380
=203.14.177.175 0.0.0.5 16 128 0 0.00000 0.000000 0.00000
I posted a version of this email here:
http://www.nelson.monkey.org/~nelson/weblog/tech/appleNTP.html
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