Basic System Configuration Guide System Management
Edition: 01 3HE 11010 AAAC TQZZA 261
• smc — SONET Minimum Clock Traceable
• eec1 — SDH Ethernet Equipment Clock Option 1 Traceable
• eec2 — SONET Ethernet Equipment Clock Option 2 Traceable
• prc — SDH Primary Reference Clock Traceable
• ssu-a — SDH Primary Level Synchronization Supply Unit Traceable
• ssu-b — SDH Second Level Synchronization Supply Unit Traceable
• sec — SDH Synchronous Equipment Clock Traceable
The user may override the received quality level value of the system synchronization
reference input by using the ql-override command to configure one of the above
values as a static value. This in turn may affect the transmitted quality level value on
each SSM-capable port. Also, the user may use the tx-dus command to force the
quality level value that is transmitted on the SSM channel to be set to dnu (do not
use) or dus (do not use for synchronization). This capability is provided to block the
interface from being a timing source for the 7705 SAR. The dus/dnu quality level
value cannot be overridden.
Figure 23 Timing Reference Selection Based on Quality Level
The G.803 and G.781 standards also define additional codes for internal use.
• QL-INVx is generated internally by the system when an unallocated
synchronization status message value is received; x represents the binary value
of this synchronization status message. Within the 7705 SAR, all these
independent values are assigned a single value of QL-INVALID.
• QL-FAILED is generated internally by the system when the terminated network
synchronization distribution trail is in the signal fail state.
• QL-UNKNOWN is generated internally by the system to differentiate from a
received QL-STU code. It is equivalent to QL-STU for the purposes of quality
level selection.
20935
T1/E1
SONET/SDH
SyncE
IEEE1588v2
ACR
2.048 MHz
5, 10 MHz
Quality Level
Override
Internal
(Node)
Timing
Reference
Ref 1
Ref 2
Ext
Ref
or
T1/E1
2.048 MHz
BITS
Qualifier
Qualifier
Qualifier
Quality
Level (QL)
Quality
Level (QL)
Quality
Level (QL)
Reference
Selector
Mode 1) Priority
reference order
Mode 2) QL then
priority reference
order
Digital Phase
Locked Loop
(DPLL)
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