Lucent Technologies 7820-0802-003 manual Using OC3-ATM ports as a clock source

	Configuring OC3-ATM Cards (MAX TNT/DSLTNT)
	Using OC3-ATM ports as a clock source
Parameter	Specifies
Tx-Cell-Payload-	Enable/disable scrambling of the 48-byte ATM cell payload in
Scramble-Disabled	transmitted cells. This function is enabled by default. Disable it by
	setting this parameter to yes only if the far-end switch has
	disabled the corresponding functions.
Loop-Timing	Enable/disable derivation of transmission timing from receiver
	inputs. Loop timing is enabled by default. If the parameter is set to
	No, transmission timing is derived from the reference clock
	instead.
VPI-VCI-Range	Valid range of VCI numbers to be used with specified VPIs for
	virtual channel connections (VCCs). For details about setting the
	VPI-VCI range, see the APX 8000/MAX TNT/DSLTNT ATM
	Configuration Guide.
Clock-Source	Enable/disable obtaining the system clock signal from the port. By
	default, ports are not eligible clock sources. For information about
	using an OC3-ATM line as the source for the system clock, see
	“Using OC3-ATM ports as a clock source” on page 15-3.
Clock-Priority	Priority of the interface as the system’s clock source: high, middle,
	or low priority. Once the TAOS unit unit chooses a clock source, it
	uses that source until the interface becomes unavailable or a
	higher-priority source becomes available.
Traffic-Shapers	Settings for shaping traffic on the interface. For details, see the
	APX 8000/MAX TNT/DSLTNT ATM Configuration Guide.
Tx-Scramble-Disabled	Enable/disable scrambling and descrambling of the entire transmit
	and receive stream. This function is enabled by default. Disable it
	only if the far-end switch has disabled the corresponding
	functions.
Tx-Cell-Payload-	Enable/disable scrambling and descrambling of the 48-byte ATM
Scramble-Disabled	cell payload in transmitted and received cells. This function is
	enabled by default. Disable it only if the far end switch has
	disabled the corresponding functions.

Using OC3-ATM ports as a clock source

OC3-ATM profiles support Clock-Source and Clock-Priority parameters for specifying whether the port can be used to source the ATM network clock signal and feed it to the shelf controller as the master clock for the unit. Each OC3-ATM port can be configured as eligible or ineligible for this use, and can be assigned a high, middle, or low priority for being elected as the clock source.

If more than one line is eligible to be the clock source, the system chooses the one with the highest priority, as specified by the Clock-Priority setting. If multiple sources of equal priority are present, the system selects the first valid clock source. (A clock source is valid if the Clock-Source parameter is set to eligible and the OC3-ATM interface is synchronized.)

Once it has selected a clock source, the system uses that source until the source becomes unavailable or a higher-priority source becomes available. If no eligible external sources are available, the system uses an internal clock generated by the shelf controller.

APX 8000/MAX TNT/DSLTNT Physical Interface Configuration Guide 15-3