363-206-295
Transmission and Synchronization Interfaces
5-22
Issue 1
December 1997
Table 5-4.
Synchronization Messages using S1 Byte
*
Synchronization messaging using the SONET K2 byte and S1 byte can be
disabled on a per OC-N interface using the
set-ocn
command (not supported by
OC-1). Zeros will be transmitted on bits 1-3 of the K2 byte if this is done; all ones
will be transmitted on bits 5-8 of the S1 byte if this is done. The timing and
synchronization status of a shelf can be determined using the
rtrv-sync
command.
The "Don't Use" message is sent when the system determines that its timing is
not suitable for synchronization; for example, due to failure.
When the DDM-2000 OC-12 system is configured for external timing and its DS1
output port is provisioned for MULT mode, the message Sync Quality Unknown
(SQU) for K byte, or Sync Trace Unknown (STU) for S byte, is sent on all the OC-N
interfaces where synchronization messaging is provisioned. When the capability
of communicating with a BITS clock over the DS1 overhead exists, the quality of
the reference signal will be transmitted instead; for example, Stratum 1.
When the DDM-2000 OC-12 system is configured for external timing and its DS1
output port is provisioned for SYNC OUT mode, the Timing Looped Back (TLB)
message for K byte, or “Don’t Use” message for S byte, will be sent on the OC-N
interfaces towards the network element (NE) from which the DS1 timing output is
being derived. The SQU message for K byte, or STU for S byte, will be sent on all
other OC-N interfaces where synchronization messaging is provisioned. If the
DS1 output is generating AIS while the system is configured in this way, the
Received Message
Active Timing
Mode
†
Default DS1
Output State
Quality
Level
Don't Use
Holdover
AIS
7
Traceable SONET minimum Clock
OK to use
AIS
5
Traceable SONET minimum Clock (w/TG3)
Holdover
AIS
5
Traceable Stratum 3 ‡§
OK to use
Good
4
Traceable Stratum 2 ‡
OK to use
Good
3
Sync Trace Unknown
OK to use
Good
2
PRS Traceable ‡
OK to use
Good
1
*
This table is applicable to OC-12 R5.1 and later releases.
†
This column applies only when provisioned for line timing mode.
‡
Presently, DDM-2000 OC-12 Multiplexers cannot generate these messages, but they
could be retransmitted and supported for autoreconfiguration if any of these are
received by DDM-2000 OC-12 Multiplexer.
§
The TG3 circuit pack can generate a stratum 3 message.
