Cisco Network Clock Ncdp Source Entry

1.3.6.1.4.1.9.9.121.1.3.1.1

Network clock status and statistics for sources of network clock identified by entPhysicalIndex and used by the managed system when the value of cncDistributionMethod is 'ncdp'. A source of network clock for the device may be an oscillator local to the device, a Building Integrated Timing Supply (BITS) port or an interface that supports synchronous clock recovery. (BITS is explained in more detail in Bell Communications Research, GR-436-CORE, 'Digital Network Synchronization Plan'.) The NCDP protocol entity selects one entry in this table to advertise as the best available clock source for the device. Cooperating NCDP protocol entities select the best available clock source among those advertised within the cooperating group and build a clock distribution tree rooted at that clock source. When the value of cncRootClockSource is used as an index into this table and the indicated clock source has cncNcdpBestClockSource with value 'true' then the indicated clock source is the root of some clock distribution tree. If only one such root exists on all participating devices in the network, then it is the root of a network wide clock distribution tree. When the managed system initializes it creates a row for the device's default source of network clock. This row cannot be destroyed by a management station. Within this row a write operation is only allowed on the cncNcdpPriority object; only read operations are allowed on all other columnar objects within this specific row. The status of this row is always active. The default source can always be found by issuing a read operation on the row within cncManualSourceTable indexed by 'default' (as the value of cncManualSourcePriority). The cncManualSourceId object contains the entPhysicalIndex of the default source of network clock and identifies it within this table. Other rows are created or destroyed by a management station or through the device's local management interface when a source of network clock is configured or removed. When a management station creates a row it creates it explicitly using RowStatus with either createAndGo or createAndWait. A row is not made active until all read-create objects not having default values are properly initialized. The values of cncNcdpPriority, cncNcdpStratum and cncNcdpPRSReference collectively describe a source of network clock, that is they are three components of a vector used as an input to the NCDP algorithm to make clock source selection decisions. The management station must make the row notInService before changing the values of any of these objects.