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997-01530-01, Rev. C-25, Jan 2008 135
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D: Network Time Protocol (NTP)
As an option, Symmetricom can factory configure the XL-GPS to function as a Stratum 1 network time
server. Network time servers use Network Time Protocol (NTP) to synchronize computer clocks across a
network. Alternatively, customers can upgrade a XL-GPS unit in the field by purchasing the NTS option
and installing a key to enable it.
Support for version 4.0 of the NTP, RFC 1305 as well as the Simple Network Time Protocol (SNTP),
RFC2030 is available. In addition, the XL-GPS responds to TIME protocol requests, RFC868.
The Network Time Server responds to time synchronization requests from hosts using these User
Datagram Protocol/Internet Protocols (UDP/IP):
NTP Packet Transmitted Timestamp Accuracy ±10 milliseconds.
Editing ntp.conf
Note: The XL-GPS is a Stratum 1 NTP server. Therefore, it does not support NTP peering, in which a
time server gets time information by sending an NTP query to another time server. Entering valid
IP addresses for the ‘server’ parameters (e.g., “
server 216.210.169.40”) in ntp.conf does not
enable peering in the XL-GPS.
The current text of “ntp.conf” is as follows:
# X L - G P S N T P . C O N F
# Load this version into the XL-GPS NTP Server for NTP MD5 and NTP broadcast
#
# The line below to enables NTP broadcast mode using MD5 key 1.
broadcast 192.168.47.255 key 1
# Trust and accept NTP packets using MD5 keys 1 or 2.
# The MD5 keys and key ID specified in the XL-GPS's NTP.KEYS file must match the
# same ones in the UNIX/Linux client NTP.KEYS file. The same keys for both
# units must be specified as trusted by the line below.
trustedkey 1 2
Type/Protocol
Port Number RFC
NTP ver. 4.0: UDP Port 123 RFC1305
SNTP: UDP Port 123 RFC2030
TIME: UDP Port 37 RFC868