Version 6.6 269 October 2014
Installation & Operation Manual 30. Time and Date Configuration
30.4 NTP Synchronization and Status
The Media Gateway synchronizes with the NTP server and updates the Operational
State and NTP Server Status attributes accordingly. The Operational State attribute
indicates whether communication is established with a specific NTP server, while the
NTP Server Status attribute indicates the “current status” of the specific NTP server,
as perceived by a local Media Gateway’s NTP client.
To understand the difference between these two attributes, consider the situation,
where two external NTP servers are used to synchronize time and date of the Media
Gateway (as shown on the above figure). When communication is established with
both servers, their Operational State attributes will be set to Enabled (and they will be
colored Green in the EMS GUI). However at any time, only one server will be chosen
as the synchronization source – its NTP Server Status will be set to Synchronized,
while another server will be used as an alternative candidate for failover; its NTP
Server Status will be set to Candidate.
Note that due to the nature of the NTP protocol implementation, there may be a
significant lag in the update of the Operational State and the NTP Server Status
attributes. For example, when the NTP server is disconnected from the IP network, it
may take up to 30 minutes until its Operational State is changed to Disabled (this
delay is introduced to prevent false failure indications in the case of intermittent
network problems). In addition, when the connection with the NTP server is re-
established, it may take up to 1 hour until the NTP Server is chosen as a
synchronization source, and its NTP Server Status attribute is updated accordingly.
In addition to the Operational State and NTP Server Status attributes, additional
status and timestamp attributes are maintained for each external NTP server. See
Table ’NTP Server Status Parameters’ for details. Use these additional attributes (e.g.
last sent and received message timestamps) to analyze the current state of the
communication with a specific NTP server and to determine possible causes for any
malfunction.
Malfunctioning or suspicious NTP server may be temporarily disabled, by changing its
Administrative State to Locked. The Media Gateway will not establish any
communication with locked NTP servers and will not update their Operational State
or NTP Server Status attributes.
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