Installing and Administering Internet Services

290 Chapter7
Configuring the Network Time Protocol (NTP)
Getting Started with NTP
ntp-cup.external.hp.com (192.6.38.127)
Location: Cupertino CA (SF Bay area) 37:20N/122:00W
Synchronization: NTPv3 primary (GPS), HP-UX
Service Area: West Coast USA
Access Policy: open access
Contact: [e-mail]
Note: no need to notify for access, go right ahead!
If you are located in Silicon Valley, you can ping this time server and see
that it is about 5 milliseconds away:
/usr/sbin/ping ntp-cup.external.hp.com 64 5
PING ntp-cup.external.hp.com: 64 byte packets
64 bytes from 192.6.38.127: icmp_seq=0. time=5. ms
64 bytes from 192.6.38.127: icmp_seq=1. time=4. ms
64 bytes from 192.6.38.127: icmp_seq=2. time=4. ms
64 bytes from 192.6.38.127: icmp_seq=3. time=5. ms
64 bytes from 192.6.38.127: icmp_seq=4. time=5. ms
----ntp-cup.external.hp.com PING Statistics---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip (ms) min/avg/max = 4/4/5
Determining Synchronization Sources
You can query the time server using ntpq -p to find out what
synchronization sources it is using:
/usr/bin/ntpq -p ntp-cup.external.hp.com
This time server is synchronized (asterisk in column one) to
REFCLK(29,1), which is a Trimble Palisade GPS receiver. The offset
from GPS is currently 0.004 milliseconds and the dispersion is 0.02
milliseconds (both excellent values, smaller is better here). This time
Table 7-2 Locating Synchronized Time Servers
remote refid st t when poll reach delay offset disp
=============================================================================
*REFCLK(29,1) .GPS. 0 l 35 32 376 0.00 -0.004 0.02
-bigben.cac.wash .USNO. 1 u 47 128 377 40.16 -1.244 1.37
clepsydra.dec.c usno.pa 2 u 561 1024 377 16.74 -4.563 4.21
-clock.isc.org .GOES. 1 u 418 1024 377 6.87 -3.766 3.57
hpsdlo.sdd.hp.c wwvb.col. 2 u 34 16 204 48.17 -8.584 926.35
+tick.ucla.edu .USNO. 1 u 111 128 377 20.03 -0.178 0.43
+usno.pa-x.dec.c .USNO. 1 u 42 128 377 6.96 -0.408 0.38