Table of Contents
Advertisement
4.2.2 SNTP
The device supports the Simple Network Time Protocol (SNTP). SNTP assures accurate network device clock time
synchronization up to the millisecond. Time synchronization is performed by a network SNTP server. SNTP operates only
as a client, and cannot provide time services to other systems.
The device can poll the following server types for the server time:
• Unicast
• Anycast
• Broadcast (Multicast)
Time sources are established by Stratums. Stratums define the distance from the device to the reference clock. The higher
the stratum (where zero is the highest), the more accurate the clock. The device receives time from stratum 1 and above.
The following is an example of stratums:
• Stratum 0 -- Indicates a real time clock is used as the time source, for example, a GPS system.
• Stratum 1 -- Indicates that a server that is directly linked to a Stratum 0 time source is used. Stratum 1 time
servers provide primary network time standards.
• Stratum 2 -- Indicates that the time source is distanced from the Stratum 1 server over a network path. For
example, a Stratum 2 server receives the time over a network link, via NTP, from a Stratum 1 server.
Information received from SNTP servers is evaluated based on the Time level and server type.
SNTP time definitions are assessed and determined by the following time levels:
• T1 -- The time at which the original request was sent by the client.
• T2 -- The time at which the original request was received by the server.
• T3 -- The time at which the server sent the server a reply.
• T4 -- The time at which the client received the server's reply.
Polling for Unicast Time Information
Polling for Unicast information is used for polling a server for which the IP address is known. T1 - T4 are used to determine
the server time. This is the preferred method for synchronizing device time.
Polling for Anycast Time Information
Figure 3-18 Reset screen
182
Advertisement
Table of Contents
