HP-UX Internet Services Administrator's Guide (February 2007)

ntp.ctr.columbia.edu (128.59.64.60) Location: Columbia University Center for Telecommunications Research; NYC
Synchronization: NTP secondary (stratum 2), Sun/Unix Service Area: Sprintlink/NYSERnet
Access Policy: open access, authenticated NTP (DES/MD5) available Contact: Seth Robertson ([e-mail])
Note: IP addresses are subject to change; please use DNS /usr/sbin/ping ntp.ctr.columbia.edu 64 5
PING 128.59.64.60: 64 byte packets 64 bytes from 128.59.64.60: icmp_seq=0. time=83. ms
64 bytes from 128.59.64.60: icmp_seq=1. time=86. ms
64 bytes from 128.59.64.60: icmp_seq=2. time=85. ms
64 bytes from 128.59.64.60: icmp_seq=3. time=86. ms
64 bytes from 128.59.64.60: icmp_seq=4. time=83. ms ----128.59.64.60 PING Statistics----
5 packets transmitted, 5 packets received, 0% packet loss round-trip (ms) min/avg/max = 83/84/86
In this example, the ping round-trip times are significantly greater than in the previous
example. 85 milliseconds is good for general NTP purposes. The dispersion
measurements are less than the ping round-trip times. The NTP daemon has a
watershed at 128 milliseconds, but this example server at 85 milliseconds is comfortably
below that. You can use the server at Columbia.
/usr/sbin/ntpq -p ntp.ctr.columbia.edu
Table 4-3 describes time servers in eastern United States.
Table 4-3 Evaluating Time Servers in Eastern United States
remote refid st t when poll reach delay offset disp
===============================================================================
+clepsydra.dec.c usno.pa-x.dec.c 2 u 927 1024 355 108.49 -18.215 3.63
otc1.psu.edu .WWV. 1 - 17d 1024 0 28.26 -25.362 16000.0
*NAVOBS1.MIT.EDU .USNO. 1 u 214 1024 377 38.48 -0.536 0.90
tick.CS.UNLV.ED tock.CS.UNLV.ED 3 u 721 1024 377 2113.97 1004.94 824.57
132.202.190.65 0.0.0.0 16 - - 1024 0 0.00 0.000 16000.0
unix.tamu.edu orac.brc.tamus. 3 u 636 1024 377 47.99 3.090 9.75
at-gw2-bin.appl 0.0.0.0 16 - - 1024 0 0.00 0.000 16000.0
-cunixd-ether.cc 192.5.41.209 2 u 172 1024 377 3.39 12.573 1.14
cunixd.cc.colum 0.0.0.0 16 u 285 64 0 0.00 0.000 16000.0
+cs.columbia.edu haven.umd.edu 2 u 906 1024 376 2.41 -5.552 15.12
+129.236.2.199 BITSY.MIT.EDU 2 u 423 1024 376 13.43 -14.707 22.60
cucise.cis.colu cs.columbia.edu 3 u 62 1024 377 5.84 -1.975 12.70
This time server at Columbia University has a variety of stratum-1, stratum-2, and
stratum-3 sources, which is good. It also has three sources which are not responding
right now (reach=0), and one with very large delay, offset, and dispersion
(tick.CS.UNLV.EDU). As before, this is due to networking problems between client
and server (New York to Las Vegas, over 3000 km), not some fault with the NTP
implementation at either end. This time server at Columbia is currently synchronized
to NAVOBS1.MIT.EDU, but three others (marked with "+" in column one) are attractive
and could step in immediately if NAVOBS1 failed for any reason.
Example 3: Evaluating Time Servers in Australia
Look at a time server in Australia. Here are the details:
ntp.adelaide.edu.au (129.127.40.3) Location: University of Adelaide, South Australia
Synchronization: NTP V3 secondary (stratum 2), DECsystem 5000/25 Unix Service Area: AARNet Access Policy: open access
Contact: Danielle Hopkins ([e-mail])
/usr/sbin/ping ntp.adelaide.edu.au 64 5
PING huon.itd.adelaide.edu.AU: 64 byte packets 64 bytes from 129.127.40.3: icmp_seq=0. time=498. ms
64 bytes from 129.127.40.3: icmp_seq=1. time=500. ms 64 bytes from 129.127.40.3: icmp_seq=2. time=497. ms
64 bytes from 129.127.40.3: icmp_seq=3. time=498. ms 64 bytes from 129.127.40.3: icmp_seq=4. time=496. ms
54 Configuring NTP