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.

Basic Principles and Planning NE IDs of Planning the DCN

When constructing the DCN, select proper communication protocols according to the actual
networking situation, and follow the planning principles.
The principles for planning the DCN are as follows:

• When Huawei OptiX OSN 2500 constructs a network with other Huawei equipment, the HWECC or IP over DCC protocol is recommended. Use the same communication protocol in the entire DCN network.
• When the OptiX OSN 2500 constructs a hybrid network with equipment from other vendors, use the IP over DCC or OSI over DCC protocol according to the protocol supported by the equipment from other vendors.
• The OptiX OSN 2500 constructs a hybrid network with equipment from other vendors. In this case, if the equipment from other vendors do not support the IP over DCC or OSI over DCC, use the DCC bytes or the Ethernet service channels to transparently transmit the management information.
• When a communication protocol is used to construct the DCN network, properly set the DCN network scale and divide the network according to the network situation. Thus, the effect of large network scale on the DCN network can be reduced.
• The DCN network should be of the ring type to ensure the reliability of the network communication. Thus, route protection can be provided when fiber cuts or NE abnormalities occur. If fibers of the equipment cannot form a ring, extra DCN channels should be constructed to form a ring, and thus the route protection function can be realized.

NE IDs are used to identify Huawei transmission equipment. Thus, the NE IDs should be

configured when the DCN network uses the HWECC, IP over DCC, and OSI over DCC

protocols.

The principles for planning the NE IDs are as follows:

• The ID of each NE should be unique.
• In the same DCN network, the ID of each NE should be unique.
• An NE ID is 24 bits in binary, which can be divided into the former eight bits and the latter 16 bits.

– The former eight bits indicate the extended ID (the default value is 9), also called the subnet number, which identifies different subnets. The subnet number cannot be 0 or 0xFF (255 in decimal).

– The latter 16 bits indicate the basic ID. The value of the basic ID cannot be 0 or 0xBFF0(49136 in decimal), or be greater than 0xBFF0.

In the ring network, the NE IDs should be increased one by one in the same direction along

the ring network.

A complex network should be divided into rings and chains. First set IDs for NEs on the

ring from 1 to N, and then set the IDs for NEs on the chain as N+1, N+2,…