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Transport overheads :
Out of the 27 transport overheads, 9 bytes are section overhead and the remaining 18 bytes are line overhead . Transport overhead provides transport information. The section overhead contains information required for communicating between successive network elements in the network, such as, repeaters. It also provides a voice communication channel for maintenance personnel. |
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The line overhead contains information to monitor line performance. This overhead provides for the following functions: |
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line performance monitoring and line maintenance |
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automatic protection switching |
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multiplexing signals |
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SONET Topology |
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SONET and SDH standards specify that the network topology be in the form of a ring. The ring contains fiber redundancies which allow traffic both unidirectionally and bidirectionally. In case of an accidental snapping of a fiber, the multiplexers can reroute the traffic along an alternate path using redundant fibers. |
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