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SDH ALARMS
The document discusses the framing structure of SDH and various alarms that can occur in SDH networks. It explains the hierarchy from STM-1 frame down to VC-4 and tributary unit levels. It then describes alarms like LOS, LOF, LOP that can happen at different levels due to issues like signal loss, missing frames, or lost pointers. It also covers alarms for indicating defects or errors like AIS, RDI, REI, BIP and methods for error monitoring using bytes in the SDH frame.
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SDH ALARMS
- 1. NBP/RTTC-MYSORE NIRANJAN Regional Telecom TrainingCenter MYSORE
- 2. SDH Framing StructureSDHFraming Structure NBP/RTTC-MYSORE
- 3. PP OO HH TUG-3TUG-3 TUG-3TUG-3 TUG-2TUG-2 TUG-2TUG-2 TU-12TU-12 TU-12TU-12 2 Mbit/s2Mbit/s Stuff C-12C-12 Overhead (PDH) VC-12VC-12 Pointer (PTR) TU-12TU-12 TU-12TU-12 TU-12TU-12 TU-12TU-12 TUG-2TUG-2 TUG-2TUG-2 TUG-2TUG-2 TUG-2TUG-2 TUG-2TUG-2TUG-3TUG-3 VC-4VC-4 VC-4VC-4 MSOHMSOH AU PointerAU Pointer VC-4VC-4 SDH Framing Structure RSOHRSOH AU-4AU-4STM-1STM-1 NBP/RTTC-MYSORE
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- 21. SDH ALARMS • LOS: When NE is unable to receive signal from other NE , due to fiber break , Tx failure of other NE,etc .It triggers Loss Of Signal • LOS is Physical Layer Alarm • There is no byte in SDH frame to indicate LOS. Its the transreceiver (SFP) which detects the in coming signal. • If no light coming to SFP it gives LOS to processor or the controlling device. Also when u get BER of orde 1 in 1000 results in LOS NBP/RTTC-MYSORE
- 22. LOS-Loss Of Signal AIS-AlarmIndication Signal RDI-Remote Defect Indication NBP/RTTC-MYSORE
- 23. Probable Causes ALARM PROBABLECAUSE 1) STM -N Port loss of signal OF cable break Rx optical power beyond thrushhold limit (local eqpt) TX forced off (Forced Laser Off at distant end) Distant ADM/TM/REG module fault Distant end power failure Local RX faulty NBP/RTTC-MYSORE
- 24. SDH ALARMS • LOF: Assuming that signal is present . • Next job is to identify STM-1 frame by means of Nx 6 bytes FAW ( 3 bytes of A1 and 3bytesA2 bytes of RSOH) . • Else it triggers Loss Of Frame NBP/RTTC-MYSORE
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- 26. LOF-Loss Of Frame AIS-AlarmIndication Signal RDI-Remote Defect Indication NBP/RTTC-MYSORE
- 27. THE NEXT STEPIS TO FIND WHERE THE VC-4S ARE LOCATED RELATIVE TO THE FAW. THIS IS ESTABLISHED BY READING THE ADMIN UNIT (AU) POINTER TO LOCATE THE J1 BYTE IN THE VC-4 POH. IF A SENSIBLE POINTER CANNOT BE FOUND, A LOSS OF POINTER (LOP) ALARM IS RAISED AT THE AU LEVEL. THIS IS USUALLY REFERRED TO AS AN AU-LOP, AU-LOP NBP/RTTC-MYSORE
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- 30. TU-LOP The next stepis to locate and read the Tributary Unit (TU) pointer for the specified TU. If a sensible pointer cannot be found, then a LOP alarm is raised at the TU level NBP/RTTC-MYSORE
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- 33. AIS (Alarm IndicationSignal) LOS, LOF, and LOP alarms will render the whole signal unusable. In this case, the missing or corrupted signal is replaced by an AIS consisting of continuous binary 1s. This will produce AIS alarms on all equipment downstream of the fault NBP/RTTC-MYSORE
- 34. AIS-Alarm Indication Signal RDI-RemoteDefect Indication NBP/RTTC-MYSORE
- 35. AIS-Alarm Indication Signal LOS-LossOf Signal RDI-Remote Defect Indication NBP/RTTC-MYSORE
- 36. AIS-Alarm Indication Signal RDI-RemoteDefect Indication NBP/RTTC-MYSORE
- 37. AIS-Alarm Indication Signal RDI-RemoteDefect Indication NBP/RTTC-MYSORE
- 38. FERF- Far EndReporting Failure RAI-Remote Alarm Indication The NE detecting the fault also sends an indication to the distant (sending) end that an alarm has been raised. This raises a FERF alarm at the appropriate level at the transmitting NE. Thus, a fault at the MS level will produce an MS-FERF. At the VC-4 level, it will produce a VC-4 FERF on some equipment, HO-FERFs. Some SDH elements refer to a remote alarm indication at some levels in the hierarchy. NBP/RTTC-MYSORE
- 39. HO FERF- FarEnd Reporting Failure NBP/RTTC-MYSORE
- 40. LO FERF- FarEnd Reporting Failure NBP/RTTC-MYSORE
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- 42. TIM-Trace Identifier Mismatch AIS-AlarmIndication Signal RDI-Remote Defect Indication NBP/RTTC-MYSORE
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- 44. EXC-Excessive Bit Errorrate( > 10x E-3) NBP/RTTC-MYSORE
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- 55. EXC-Excessive Bit Errorrate( > 10x E-3) NBP/RTTC-MYSORE
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- 61. EXC-Excessive Bit Errorrate( > 10x E-3) NBP/RTTC-MYSORE
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- 64. LOM-Loss Of Multiframe NBP/RTTC-MYSORE
- 65. ERROR MONITORING NBP/RTTC-MYSORE B1 byteis used to check for errors in the RS. B2 byte is used to check for errors in the MS. B3 byte is used to check for errors in the VC-4 path. V5 byte is used to check for errors in the VC-12 path.
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- 67. BIP-Bit Interleaving Parity B1,B2,B3& B5 bytes are used for Error Detection in specific section and path . This is based upon BIP detection mechanism NBP/RTTC-MYSORE
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