DEFINITY Enterprise Communications Server Release 7
Maintenance for R7r
555-230-126
Issue 4
June 1999
Maintenance Object Repair Procedures
9-1563SYNC (Synchronization)
9
Stratum 4 Synchronization
The system can be configured with primary and secondary synchronization
references (DS1 or UDS1 interface circuit packs) when using Stratum 4
synchronization. If this is the master synchronization source for the network, then
its local oscillator is used and no DS1s are used as references. If this system is a
slave in the network, a primary reference must be used as the synchronization
reference and the secondary reference is optional:
■ If the primary synchronization reference is not providing a valid timing
signal, the system automatically switches to the secondary
synchronization reference.
■ If the primary synchronization reference is invalid and secondary
reference does not provide a valid timing signal or is not administered as a
synchronization reference, a Tone-Clock circuit pack provides the system
timing source.
■ If the system is using the local oscillator as the timing source (both the
primary and secondary references are providing invalid timing signals),
should either the primary or secondary reference becomes valid again,
the system switches back to the primary or secondary source.
■ When both the primary and secondary source become valid, the system
switches to the primary source, since the primary source is always
preferred over the secondary source when both sources are equally
healthy.
If the primary synchronization reference is providing a valid timing signal, then
the flow of system synchronization would travel from the DS1 interface circuit
pack in the PPN across the active PPN to EPN fiber links to the two EPNs. The
PPN DS1 interface circuit pack provides a timing signal for the PPN Tone-Clock
circuit pack and the PPN Tone-Clock circuit pack provides timing for all circuit
packs in the PPN. Each PPN Expansion Interface circuit pack uses the timing
generated by the Tone-Clock circuit pack to clock data from the fiber links to the
Expansion Interface circuit packs in the two EPNs. The active EPN Expansion
Interface circuit pack uses the received data stream to generate a timing signal.
The Tone-Clock circuit packs in the EPNs use this signal to generate timing for all
the circuit packs in their respective EPNs. The PPN, in the above mentioned
scenario, is designated the
master
port network and the EPNs are called
slave
port networks. The
master
port network is defined as the port network that
contains the system synchronization source. If the primary synchronization
reference does not provide a valid timing signal, Synchronization Maintenance
will switch to the secondary reference.
Both the primary and secondary
references must reside in the same port network, which may be any port network.
The PPN is the recommended location.
If TDM-CLK error 2305 is in the error log, then a slave Tone-Clock loss of signal
condition exists on the slave Tone-Clock circuit pack that has this error. If only
one loss of signal occurred, the slave Tone-Clock circuit pack is receiving the
timing signal from the standby EI circuit pack (in this example, the timing is
