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The services are interrupted due to incorrect tributary attributes in the case of an MSPR protection switching

Publication Date:  2012-07-24 Views:  51 Downloads:  0
Issue Description

A 622 M MSPR consists of different types of equipment. The IDs of such equipment are 38, 44, 41, 42, and 43 in order. NE 38 is an OptiX 2500+ equipment, NE 44 is an OptiX 155/622H equipment, and all other NEs are OptiX 155/622 equipments. The customer reports that the services of the whole ring are switched over when the 10-SD4-2 optical board on NE 38 fails. The services on NE 44 have been interrupted for nine minutes. The services on all other stations are normal.

The NE software version of the OptiX 2500+ is 4.5.4.16. The NE software version of the OptiX 155/622H is 4.02.06.04P01      
Alarm Information
The tributary channel of NE 44 reports PS alarms. The switching alarms of other NEs are normal.      
Handling Process
The data analysis shows that the services are interrupted due to channel switching during the MSPR protection switching. The channel switching occurs due to the wrong setting of the channel attribute of the 4-PD2D board on NE 44. Ask the field engineers to set the attribute to Non protection, and suggest that they carry out MSPR protection switching at night.      
Root Cause
1.Check whether the MSPR protection switching is normal:
The alarms and K bytes of NEs 38 and 44 show that the MSPR protection switching is normal. NE 44 has too many K bytes that are wrapped, so we check the K bytes of NE 38:
 sys2              41        SF_DET            0x0002  2007-07-09 09:50:12  0x3cd8a524  //The optical board fails. NE 38 detects a signal failure alarm.
sys2              59        XC_EXECUTE        0x0002  2007-07-09 09:50:12  0x3cd8dd3a 
  sys2              60        STATE_TRAN        0xb004  2007-07-09 09:50:12  0x3cd8e210
//The MSPR protection switching is normal.
sys2              61        K_RECV            0xb01a  2007-07-09 09:50:12  0x3cd8edcf 
  sys2              62        K_DIR             0x0000  2007-07-09 09:50:12  0x3cd8edef 
  sys2              63        SF_DET            0x0002  2007-07-09 09:50:13  0x3cef7db4
2.Check whether exceptional alarms exist:
The check shows that the tributary channel of NE 44 reports PS alarms. The MSPR performs switching of the cross connection by using the related protocol and does not involves switchover of channels.
297     11    MSRDI   minor       end      2007-7-9 9:51:4    2007-7-9 9:51:6      0x01ffff01 
  285     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x01ffff04 
  286     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x02ffff04 
  287     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x03ffff04 
  288     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x04ffff04 
  289     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x05ffff04 
  290     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x06ffff04 
  291     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x07ffff04 
  292     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x08ffff04 
  293     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x09ffff04 
  294     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x0affff04 
  295     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:41     0x0bffff04 
  296     4     PS       major       end      2007-7-9 9:51:4    2007-7-9 10:0:43     0x0cffff04
It is believed that the protection attribute of the tributary channel is set to Protection. In this case, switchover of the channel also occurs when the active bus receives the alarm indication signal (AIS). Check and find that the attribute of each tributary channel of NE 44 is set to Protection.
#0x9002c:cfg-get-bscfg:4,pd2d
    STATE   : 1                                                              
   PSMODE   : p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p p
   PMODE  : 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4  
   LOPBACK  : nolb nolb nolb nolb nolb nolb nolb nolb nolb nolb nolb nolb    
              nolb nolb nolb nolb nolb nolb nolb nolb nolb nolb nolb nolb    
              nolb nolb nolb nolb nolb nolb nolb nolb     
3.Protection switching of tributary channels also occurs during the MSPR switching. 
Now the fault is located. When the optical board fails (2007-7-9 9:51:4), the optical board on NE 44 detects the signal failure alarm and then originates MSPR protection switching. In addition, the tributary card on NE 44 detects the AIS of the active channel, so the services are immediately switched to the standby channel. The MSPR protection switching takes a longer time than the channel switching does, so the channel switching has completed when the MSPR protection switching completes. In this case, the services run through the standby channel. As a result, the services are interrupted because the standby channel fails. The channel switching recovers after 10 minutes and the services are switched back to the active channel. In this case, the services recover.
For more information on the cause analysis, see the attachment.       
Suggestions
It is recommended to check the attributes of all tributary channels on the local network. On an MSPR or a chain network, set the channel attributes to Non protection. On a channel ring or an SNCP ring, set the tributary channel attribute to Protection.      

END