Nokia 7705 - 6.4.9.1 Timing Reference Selection Based on Quality Level

System Management
264
Basic System Configuration Guide
3HE 11010 AAAC TQZZA Edition: 01
2. These quality level indications are considered to be lower than the internal clock of the system.
They are relayed to the line interfaces when ql-selection is disabled. When ql-selection is enabled,
these inputs are never selected. If there is no valid reference available for the internal clock, then
the clock enters holdover mode and the quality level is QL-UNC.
6.4.9.1 Timing Reference Selection Based on Quality Level
For a SONET/SDH interface, a BITS DS1 or E1 physical port, or an E1 port interface
that supports SSM, or for a synchronous Ethernet interface that supports ESMC, a
timing input provides a quality level value to indicate the source of timing of the far-
end transmitter. These values provide input to the selection processes on the nodal
timing subsystem. This selection process determines which input to use to generate
the signal on the SSM egress ports and the reference to use to synchronize the nodal
clock, as described below.
• For the two reference inputs (ref1 and ref2) and for the BITS input ports, if the
interface configuration supports the reception of a QL over SSM or ESMC, then
the quality level value is associated with the timing derived from that input.
• For the two reference inputs and for the BITS input ports, if the interface
configuration is T1 with SF framing, then the quality level associated with the
input is QL-UNKNOWN.
• For the two reference inputs, if they are synchronous Ethernet ports and the
ESMC is disabled, then the quality level value associated with that input is
QL-UNKNOWN.
• For the two reference inputs and for the BITS input ports, if the interface
configuration supports the reception of a QL over SSM (and not ESMC), and no
SSM value has been received, then the quality level value associated with the
input is QL-STU.
• For the two reference inputs and for the BITS input ports, if the interface
configuration supports the reception of a QL over SSM or ESMC, but the quality
level value received over the interface is not valid for the type of interface, then
the quality level value associated with that input is QL-INVALID.
• For the two reference inputs, if they are external synchronization, DS3, or E3
ports, then the quality level value associated with the input is QL-UNKNOWN.
• For the two reference inputs, if they are synchronous Ethernet ports and the
ESMC is enabled but no valid ESMC Information PDU has been received within
the previous 5 s, then the quality level value associated with that input is QL-
FAILED.
• If the user has configured an override for the quality level associated with an
input, the node displays both the received and override quality level value for the
input. If no value has been received, then the associated value is displayed
instead.