Synchronization Status Messages - Nortel Optical Multiservice Edge 6130 Planning Manual

When a timing reference becomes available again, the synchronization
hardware automatically transitions to locked mode. The synchronization
hardware remains in holdover mode for a minimum of 24 hours. After
holdover mode, the synchronization hardware enters the freerun mode.

Synchronization status messages

Synchronization status messages (SSM) indicate the quality of the timing
signals currently available to a network element. The timing sources that can
be provisioned in a network element include external timing (ESI), line timing
(timing derived from STM-1/4 interfaces or E1 signals), and the internal clock
of the network element.
A network element can select the best of the two timing signals provided by
the timing sources provisioned by the user. The selection is based on the
quality values carried in the SSMs if the quality mode is enabled, otherwise,
the selection is based on the priority level set by the user. As the timing passes
from one network element to the next, each network element sends SSMs. If
the quality of the timing changes, the SSMs inform the next network element
of the change.
If a timing reference is not to be used for synchronization, the SSM will
contain a do not use for synchronization (DNU) message. See
page 6-11 for an overview of SSM designations supported by OME6130 in
SDH mode.
Table 6-4
Synchronization status messages in SDH mode
Description
Traceable to Primary Reference Clock
Traceable to Transit Clock
Traceable to Local Clock
Traceable to SDH Equipment Clock
Do Not Use for Synchronization
Note 1: If the incoming quality level is not recognized by the OME6130,
the quality level is displayed as invalid. To use a timing source with an
invalid quality level as a timing reference, the user must override the
invalid quality level.
Note 2: The incoming quality level can not be overwritten if the timing
source is an STM-1/4 interface port.
Planning Guide NT6Q92MA Rel 1.0 Iss 1 Standard September 2006
OAM&P description 6-11
Designation Quality
Level
PRC 2
SSU-A 4
SSU-B 8
SEC 11
DNU 15
Table 6-4 on
S1 bits (5-8)
0010
0100
1000
1011
1111