Hi,
You access the time settings via the OS Administration page.
You can as you say either use an NTP Server or the Callmanager.
To use a NTP Serer then use the Settings>NTP Servers option and then click Add and enter the IP address or hostname.
If you are using the CallManager then use the Settings>Time section and enter the time. You cannot use both, if you have an NTP server configured already then you need to delete it to modify the time which uses the CallManager as its time source.
You are better off using a suitably accessable NTP source as these are more accurate.
Do not get confused with the Phone NTP reference in the CallManager System Menu as this is for SIP phones only.
Some info on NTP
Network Time Protocol
Network Time Protocol (NTP) is a protocol for synchronizing the clocks of computer systems over IP networks through use of a hierarchical clock strata organization. The measurement uses a system known as Stratums.
A stratum level 1 timing source device is an extremely precise clock source using the rare earth element cesium. Cesium clocks used to be very expensive, but most service providers with large central offices now have local stratum level 1 clocks. Global positioning system (GPS) satellites provide a stratum level 1 clocking source that provides a cost-effective synchronization system.
Stratum level 2 timing sources are based on the rare earth element rubidium. Distribution of stratum 2 time information becomes inaccurate more quickly than stratum 1 information. Stratum level 2 timing is not as accurate as stratum level 1.
Stratum level 3 timing sources are based on the rare earth element quartz, which has become affordable enough that it is built in to most off-the-shelf wristwatches.
CUCM has an option to use NTP to obtain time information from a time server. Only the CUCM publisher will communicate with one or more NTP servers. The timing that the publisher receives is synchronized to the subscriber servers.
If an external NTP server is not used, CUCM can be manually configured with the date and time. The system time in most servers is a stratum level 4 timing source and should not be relied on to time a production network.
Hope this helps
Paul
