Description: The method used to distribute network clock for the device. When the mode of operation is 'ncdp', the services provided by the NCDP entity are in use. When this is the case, NCDP entities residing on adjacent nodes exchange protocol messages that are used by the resident NCDP entity to select clock source such that a network-wide clock distribution tree is constructed. When the mode of operation is manual, the NCDP entity is not in use and sources of network clock are statically configured. When this is the case, the construction of a network-wide clock distribution tree is done manually by a network administrator or NMS application.