Network Configuration Requirements. Board Configuration Requirements. Equipment-Level Protection Configuration Requirements, страница 10

A.6.2  Clock Configuration with Standard SSM Enabled

Standard SSM, a mechanism for synchronization management in SDH network, allows switching the quality information of clock source among nodes, thus the OptiX OSN 3500 can automatically choose the clock source of the highest quality and priority to prevent the occurrence of clock mutual tracing, as shown in Figure A-15. Standard SSM is loaded in the lower four-digit bits (bit5 – bit 8) of the S1 byte in SDH section overhead.

Figure A-15 SSM application

A.6.3  Clock Configuration with Extension SSM Enabled

However, Standard SSM cannot avoid the clock mutual tracing completely, as shown in Figure A-16. Huawei puts forward the concept of clock source ID, which is defined using the higher four-digit bits (bit1–bit4) of the S1 byte and transmitted with SSM. The SSM with clock ID is called extension SSM. When a node receives the S1 byte, it checks the clock source ID to judge whether it is originated from this station. If so, the clock source is unavailable, thus the clock mutual tracing can be avoided, as shown in Figure A-17.

Figure A-16 Clock mutual tracing occurs when enabling SSM

Figure A-17 Application of clock source ID

A clock ID can be allocated by NM or set manually. In an SDH ring network, the clock ID is usually set manually to effectively prevent the occurrence of mutual tracing. The clock ID is necessary only in key points, set the clock ID following the principles below.

n  Allocate a clock ID for every external BITS.

n  Allocate a clock ID for the internal clock source of every node with external BITS.

n  Allocate a clock ID for the internal clock source of the junction node of a ring and chain or two rings.

n  For a junction node, if the clock tracing level includes ring clock source, allocate a clock ID for this clock source.

A.6.4  Examples of Clock Configuration

Here introduces the clock configuration in chain network, tangent ring and intersecting ring network.

1.  Clock Configuration in Chain

Clock mutual tracing will not occur to a chain network with SSM enabled. If there are more than 20 nodes, a BITS clock should be added for compensation, as shown in Figure A-18.

Figure A-18 Clock configuration in chain

2.  Clock Configuration on Tangent Rings

The clock configured on tangent rings is shown in Figure A-19.

Figure A-19 Clock configuration on tangent rings

3.  Clock Configuration on Intersecting Rings

The clock configured on an intersecting rings is shown in Figure A-20.

Figure A-20 Clock configuration on intersecting rings

A.7  Auxiliary Interface Configuration Requirements

The OptiX OSN 3500 provides serial ports Serial 1, Serial 2, Serial 3, and Serial 4 (hereinafter called S1, S2, S3, S4) with the function listed in Table A-21.

Table A-21 Function of serial ports S1–S4

Serial port	Electrical standard	Rate	Functions	Configuration mode
S1–S4	RS232/RS422	19.2 kbit/s	Environment monitoring, microwave monitoring	Point to point, broadcast

Figure A-21 shows an example of environment and microwave monitoring using S1–S4.

Figure A-21 Auxiliary interface configuration

S2 is configured as point-to-point mode to monitor the microwave stations. S1 is configured as broadcast mode. The S1 of NE1 sends broadcasting, upon receiving the broadcasting, NE20, NE21, NE22 will return the value of environment they monitor.