SDH ALARMS AND RESONS FOR THE SAME

1. NBP/RTTC-MYSORE
NIRANJAN
Regional Telecom Training Center
MYSORE

2. SDH Framing StructureSDH Framing 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/s2 Mbit/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-Alarm Indication Signal
RDI-Remote Defect Indication
NBP/RTTC-MYSORE

23. Probable Causes
ALARM PROBABLE CAUSE
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-Alarm Indication Signal
RDI-Remote Defect Indication
NBP/RTTC-MYSORE

27. THE NEXT STEP IS 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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29. LOP-Loss Of Pointer
NBP/RTTC-MYSORE

30. TU-LOP
The next step is 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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32. LOP-Loss Of Pointer
NBP/RTTC-MYSORE

33. AIS (Alarm Indication Signal)
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-Remote Defect Indication
NBP/RTTC-MYSORE

35. AIS-Alarm Indication Signal
LOS-Loss Of Signal
RDI-Remote Defect Indication
NBP/RTTC-MYSORE

36. AIS-Alarm Indication Signal
RDI-Remote Defect Indication
NBP/RTTC-MYSORE

37. AIS-Alarm Indication Signal
RDI-Remote Defect Indication
NBP/RTTC-MYSORE

38. FERF- Far End Reporting 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- Far End Reporting Failure
NBP/RTTC-MYSORE

40. LO FERF- Far End Reporting Failure
NBP/RTTC-MYSORE

41. BIP-Bit Interleaving Parity
NBP/RTTC-MYSORE

42. TIM-Trace Identifier Mismatch
AIS-Alarm Indication Signal
RDI-Remote Defect Indication
NBP/RTTC-MYSORE

43. BIP-Bit Interleaving Parity
NBP/RTTC-MYSORE

44. EXC-Excessive Bit Error rate( > 10x E-3)
NBP/RTTC-MYSORE

45. BIP-Bit Interleaving Parity
NBP/RTTC-MYSORE

46. RDI-Remote Defect Indication
NBP/RTTC-MYSORE

47. REI-Remote Error Indication
NBP/RTTC-MYSORE

48. DEG-Degradation
NBP/RTTC-MYSORE

49. UNEQ- UNEQuipped
NBP/RTTC-MYSORE

50. TIM-Trace Identifier Mismatch
NBP/RTTC-MYSORE

51. BIP-Bit Interleaving Parity
NBP/RTTC-MYSORE

52. RDI-Remote Defect Indication
NBP/RTTC-MYSORE

53. REI-Remote Error Indication
NBP/RTTC-MYSORE

54. DEG-Degradation
NBP/RTTC-MYSORE

55. EXC-Excessive Bit Error rate( > 10x E-3)
NBP/RTTC-MYSORE

56. PLM-Path Load Mismatch
NBP/RTTC-MYSORE

57. TIM-Trace Identifier Mismatch
NBP/RTTC-MYSORE

58. RDI-Remote Defect Indication
NBP/RTTC-MYSORE

59. REI-Remote Error Indication
NBP/RTTC-MYSORE

60. DEG-Degradation
NBP/RTTC-MYSORE

61. EXC-Excessive Bit Error rate( > 10x E-3)
NBP/RTTC-MYSORE

62. PLM-Path Load Mismatch
NBP/RTTC-MYSORE

63. UNEQ- UNEQuipped
NBP/RTTC-MYSORE

64. LOM-Loss Of Multi frame
NBP/RTTC-MYSORE

65. ERROR MONITORING
NBP/RTTC-MYSORE
B1 byte is 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
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