Section overhead
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In Synchronous optical networking the section overhead consists of the Regenerator Section, Pointer mechanism, and Multiplexer section, making a total of 81 bytes, (channels) of overhead information. A total of 5.184Mb/s. The Regenerator Section of the Overhead consists of the following channels:-
A1/A2 - Frame Alignment, J0 - Trail Trace, Path Identifier, (a customer specified string, or security), B1 - Error monitoring, BIP-8, (Bit Interleaved Parity, using bit 8), E1 - Engineering Order-Wire, F1 - Maintenance, or customer specified, D1/D2/D3 - Embedded, SDH specific, (DCCr), channels used for management by the TMN (192kB/s).
The Pointer mechanism channels:-
H1/H2/H3 - Give the start of individual containers within the payload for easy retrieval.
The Multiplexer section channels:-
B2 - Error monitoring, BIP-24, (Bit Interleaved Parity, using 8 bits from 3 channels), K1/K2 - Automatic Protection Switching to back up circuits/lines, S1 - Synchronisation Status Message, (SSM), for clock quality monitoring, D4-D12 - Embedded, (DCCm), management (TMN), or customer specified channels, (512kB/s). M1 - to be continued.....
