Stmo oh bytes
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The document describes overhead bytes in the Synchronous Optical Networking (SONET) and Synchronous Digital Hierarchy (SDH) protocols. It explains that certain bytes, such as J0 and B1, are used for regenerator section trace and byte interleaved parity to ensure connection integrity and identify individual signals after multiplexing. Other bytes, like D1-D3 and E1, are used for embedded operations channels and orderwires. The document also describes pointer bytes H1-H3 that indicate the offset of the synchronous payload envelope and compensate for timing variations, and Maintenance overhead bytes like B2, K1-K2, and S1 that provide automatic protection switching, additional data communications, and
Stmo oh bytes
- 1. Data ComD4Data ComD6Data ComD5Data ComD7Data ComD9Data ComD10Data ComD11Data ComD12STM-0 OverheadsHO PathOverheadSectionOverhead FramingA1Path TraceJ1FramingA2RS TraceJ0R-SectionOverheadBIP-8B3BIP-8B1OrderwireE1User ChannelF1Data ComD3Data ComD1Data ComD2Signal LabelC2Path StatusG1PointerH2PointerH1PointerH3AU pointerAPSK2APSK1User ChannelF2BIP-8B2Multiframe IndicatorH4M-SectionOverheadUser ChannelF3Data ComD8APSK3TandemN1(REI)(M1)OrderwireE2SyncS1
- 2. RSOH Bytes :A1, A2 - framing bytes.J0 - regenerator section trace (in early SONET a counter called C1).Enables receiver to be sure that the section connection is still OK.Enables identifying individual STS/STMs after muxing.B1 Byte Interleaved Parity-8 byteeven parity of bits of bytes of previous frame after scramblingonly 1 BIT-8 for multiplexed STS/STME1 section orderwire64 kbps voice link for technicians from regenerator to regeneratorF1 64 kbps link for user purposesD1 + D2 + D3 192 kbps messaging channel used by section termination as Embedded Operations Channel (SONET) or Data Communications Channel (SDH)
- 3. AU Pointers :Pointer (H1, H2)Two bytes used to indicate the offset between the pointer bytes and the first byte of the SPEAlso indicates concatenationPointer Action (H3)Used to compensate for the SPE timing variationsPositive/negative stuff bytes-To compensate for clock differences - When negative justification tributary rate is above nominal, negative justification is needed.H3 carries the extra data. - When positive justification tributary rate is below nominal, positive justification is needed, byte after H3 is stuffing bytePointer bytes tell when H3 is being used
- 4. MSOH Bytes :B2 BIP-8 of line overhead + previous envelope (w/o scrambling)N B2s for muxed STM-NK1 and K2 are used for Automatic Protection Switching.D4 D12 are a 576 Kbps Data Communications Channelbetween multiplexers,usuallymanufacturer specific OAM functionsS1 Synchronization Status Messageindicates stratum level (unknown, stratum 1, , do not use)M0 Far End Block Errorindicates number of BIP violations detectedE2 line orderwire64 kbps voice link for technicians from line mux to line mux