Capabilities of Supporting Clocks on Huawei OSN2500

The clocks supported by the equipment and the clock protection are defined.

Basic Functions

Huawei OptiX OSN 2500 have the following functions:
Tracing of the external clock source, line clock source, tributary clock source and internal
clock source.
Non-SSM, standard SSM and extended SSM.
Clock working modes compliant with ITU-T G.781, such as locked, hold-over, and free
run.
Output of the line clock, tributary clock and external clock.
Tributary re-timing.
ASON clock tracing scheme.

Clock Protection

Huawei OptiX OSN 2500 can realize the clock protection switching in the following ways:
l Do not enable the SSM, and then perform the clock source selection and switching
according to the priority list. In this case, do not configure two clocks in two directions on
one NE into the priority list. Otherwise, the clocks form a loop.
l Enable the standard SSM mode, and then configure the priority list to ensure that the OptiX
OSN 2500 can automatically select the clock source with the highest priority to avoid the
locked loop.
l Enable the extended SSM mode. Use the fifth to eighth bits of the S1 byte to define the
quality of the clock source, and use the first to fourth bits of the S1 byte to define the clock
source ID. Thus, the clock loop can be avoided. The principles for setting the clock IDs are
as follows:
– All external BITSs should be assigned with clock IDs.
– In the case of nodes with external BITSs, the internal clocks of these nodes should be
assigned with clock IDs.
– In the case of nodes that access the chain or ring network to another ring network, the
clock sources of these nodes should be assigned with clock IDs.
– In the case of nodes that access the chain or ring network to another ring network, when
the clock tracing level includes the line clock source, the line clock sources accessed to

another ring network should be assigned with clock IDs.