D-Link DFL-2500 - Manual (Page 84)

Time Synchronization Protocols are standardised 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 accesible 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.
Important
Make sure an external DNS server is configured so that Time Server URLs can be
resolved (see Section 3.9, “DNS Lookup”). This is not needed if using server IP
addresses.
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.
CLI
gw-world:/> set DateTime TimeSynchronization=custom TimeSyncServer1=dns:ntp1.sp.se
TimeSyncServer2=dns:ntp2.sp.se TimeSyncInterval=86400
Web Interface
1. Go to System > Date and Time
2. Check the Enable time synchronization
3. Now enter:
• Time Server Type: SNTP
• Primary Time Server: ntp1.sp.se
• Seconadry Time Server: ntp2.sp.se
4. Click OK
Note
If the TimeSyncInterval parameter is not specified when using the CLI to set the
synchronization interval, the default of 86400 seconds (= 1 day) is used.
Example 3.24. Manually Triggering a Time Synchronization
Time synchronization can be triggered from the CLI. The output below shows a typical response.
3.8.2. Time Servers Chapter 3. Fundamentals
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