Enabling Time Synchronization Using Sntp - D-Link DFL-260E User Manual

3.8.3. Time Servers
The hardware clock which NetDefendOS uses can sometimes become fast or slow after a period of
operation. This is normal behavior in most network and computer equipment and is solved by
utilizing Time Servers.
NetDefendOS is able to adjust the clock automatically based on information received from one or
more Time Servers which provide a highly accurate time, usually using atomic clocks. Using Time
Servers is highly recommended as it ensures NetDefendOS will have its date and time aligned with
other network devices.
Time Synchronization Protocols
Time Synchronization Protocols are standardized methods for retrieving time information from
external Time Servers. NetDefendOS supports the following time synchronization protocols:
• SNTP
Defined by RFC 2030, The Simple Network Time Protocol (SNTP) is a lightweight
implementation of NTP (RFC 1305). This is used by NetDefendOS to query NTP servers.
• UDP/TIME
The Time Protocol (UDP/TIME) is an older method of providing time synchronization service
over the Internet. The protocol provides a site-independent, machine-readable date and time. The
server sends back the time in seconds since midnight on January first, 1900.
Most public Time Servers run the NTP protocol and are accessible using SNTP.
Configuring Time Servers
Up to three Time Servers can be configured to query for time information. By using more than a
single server, situations where an unreachable server causes the time synchronization process to fail
can be prevented. NetDefendOS always queries all configured Time Servers and then computes an
average time based on all responses. Internet search engines can be used to list publicly available
Time Servers.
Example 3.23. Enabling Time Synchronization using SNTP
In this example, time synchronization is set up to use the SNTP protocol to communicate with the NTP servers at
the Swedish National Laboratory for Time and Frequency. The NTP server URLs are ntp1.sp.se and ntp2.sp.se.
Command-Line Interface
gw-world:/> set DateTime TimeSynchronization=custom
Web Interface
1. Go to System > Date and Time
2. Check the Enable time synchronization
Important: DNS servers need to be configured in NetDefendOS
Make sure at least one external DNS server is correctly configured in NetDefendOS so
that Time Server URLs can be resolved (see Section 3.9, "DNS"). This is not needed if
using IP addresses for the servers.
TimeSyncServer1=dns:ntp1.sp.se
TimeSyncServer2=dns:ntp2.sp.se
TimeSyncInterval=86400
139
Chapter 3. Fundamentals