Writing none(1) to this object indicates to use the local system time. When the value is set to none(1), h3cSysClockProtocolSrcMdc and h3cSysClockProtocolSrcContext cannot be written and the value will be set to invalid. Change system time will be performed through the node of h3cSysLocalClock and h3cSysSummerTime. Writing ntp(2) to this object indicates to use NTP time source. NTP means Network Time Protocol. To get the system time through NTP, NTP must be configured successfully. NTP time source can be obtained from non-default MDC and non-default context. When ntp(2) is set, the system time can't be changed manually. Support for this keyword depends on the device model. Writing ptp(3) to this object indicates to use PTP time source. PTP means Precision Time Protocol. To get clock time through PTP, PTP must be configured successfully. PTP time source can be obtained from non-default MDC but cannot be obtained from non-default context. When ptp(3) is set, the system time can't be changed manually. Support for this keyword depends on the device model. Writing interface(4) to this object indicates to get time source from interface. To get clock time through interface, interface must be configured successfully. When interface(4) is set, the system time can't be changed manually. Support for this keyword depends on the device model. All MDCs on the device share the same time source and use the same system time. The shared time source can be one of the following items: Local system time - the time signal that is generated by the local crystal oscillator Remote time source - the time signal that is obtained by the specified MDC from another device on the network.