HP-UX Internet Services Administrator's Guide (May 2010)

The time server ntp-cup.external.hp.com is the appropriate time server because
it is only 5 milliseconds from the NTP client and it the right choice for a public time
server. The ping command round-trip time determines whether this time server is the
right choice for a public time server.
Example 2: Evaluating Time Servers in Eastern United States
For a time server located on the east coast of Northern America, following are the
details:
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
52 Configuring NTP