363-206-285
Transmission and Synchronization Interfaces
5-40 Issue 3 June 2001
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-3 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-3 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 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
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 Clock minimum (w/TG3) Holdover AIS 5
Traceable Stratum 3 ठOK 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
* S1 byte not supported on OC-1 links.
† This column applies only when provisioned for line-timing mode.
‡ Presently, DDM-2000 OC-3 Multiplexers cannot generate these messages, but they
could be retransmitted and supported for autoreconfiguration if any of these are
received by a DDM-2000 OC-3 Multiplexer.
§ The TG3 circuit pack can generate a stratum 3 message.
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