Mike's PBX Cookbook

2.0 Mb PRI Maintenance

Red alarm (local alarm)
  • Circuit problems
  • Hardware failure
  • Receive pair open
  •   Yellow alarm (remote alarm)
  • The far end is not ready, or out of service
  • Receiving this alarm proves link integrity!
  • Transmit pair open
  • Alarms

    Red: Near End Alarm (NEA)

    When a Red alarm occurs, all B-channels are disabled. See PRI problems for possible solutions.
    When the alarm is cleared, the PRI is automatically restored to service, and B-channels enabled.

    Check the PRI Status and reset the counters in LD 60:

    1. STAT loop - check PRI status
    2. LCNT loop - list alarm counters
    3. RCNT loop - reset alarm counters

    Yellow: Far End Alarm (FEA)

    When a Yellow alarm occurs, all B-channels are disabled, and an alarm counter is incremented.
    When the alarm is cleared, the PRI is automatically restored to service, and B-channels enabled.

    BUT, if the 24-hour threshold (prompt RALM in LD 73) is reached, the PRI must be manually restored to service.

    When the alarm is cleared, reset the counters and bounce (disable, then enable) the PRI in LD 60:

    1. LCNT loop - list alarm counters
    2. RCNT loop - reset alarm counters
    3. DISL loop - disable loop
    4. ENLL loop - enable loop

    Counters

    Counters are split into Group 1, Group 2, and 24 hour Group 2 total alarms. A healthy PRI will return zeros:

    .lcnt 201
    
    PRI2 LOOP  201
         MNT  NNDC   NNC   OOS
    BPV- 000   000   000   000
    FAP- 001   000   000   000
    SLP- 000   000   000   000
    CRC- 000   000   000   000
    G2 - 000   000   000   000
                     MAINT      NONEWCALL  UNAVAIL    SEVERE
    TOTAL 24HR BPV - 000000000  000000000  000000000  000000000
    TOTAL 24HR CRC - 000000000  000000000  000000000  000000000
    TOTAL 24HR FAP - 000000008  000000000  000000000  000000000
    TOTAL 24HR SLPREP - 000000000
    TOTAL 24HR SLPDEL - 000000000
    TOTAL 24 HOUR G2 AIS  -000000000
    TOTAL 24 HOUR G2 LFAS -000000000
    TOTAL 24 HOUR G2 LMAS -000000000
    TOTAL 24 HOUR G2 RAI  -000000000
    TOTAL 24 HOUR G2 LOS  -000000000
    TOTAL 24 HOUR G2 RAIE -000000000
    .
    
    Group 1 Alarms:
    BPVBipolar Violations
    FAPFrame Alignment Problems
    SLPFrame Slips
    CRCCyclic Redundancy Check
     
    Group 2 Alarms:
    AISAlarm Indication Signal
    LFASLoss of Frame Alignment
    LMASLoss of Multi-frame Alignment
    RAIRemote Alarm Indication
    LOSLoss of Signal

    Group 1 alarms are event-driven and include indicators that decrement a counter whenever an error is detected. Grade-of-service is changed based on how quickly the threshold of the counter is exceeded. The threshold count is determined in LD 73.

    Group 2 alarms are either continuous or discontinuous. Grade-of-service is changed based on the duration of the alarm within a defined period of time. A minimum persistence time is defined in LD 73.  

    PRI Circuit problems

    The PRI can have any of the following problems. Determine the cause of the problem and follow the recommended actions:

    SymptomAction
    No connection to far end.

    (If you are not physically connected to the far end, frame-alignment errors occur. The channels will be disabled, the PRI will be in local-alarm mode.)

    Check for wiring problems:
    • Receive pair open
    • Receive and transmit pairs open
    • Corrupted data on receive pair
    PRI fails self-test.Replace the PRI card (not very common!).
    Far-end problems, usually indicated by a remote alarm.Check PRI status, and your local transmit pair integrity.
    Contact the far end to determine what action they are taking.
    PRI is connected but getting bit-rate or frame errors.

    This can be caused by:

    • bad or noisy cable connections
    • electrical or electromagnetic interference
    • carrier problems (for example, defective repeater)
    Verify the wiring, and physical connection integrity.

    If the PRI in local alarm was a primary clock source, the software switches the clock controller to the secondary reference.

    Check the Clock Controller is enabled and locked.

    Configuration settings do not match the far end.

    These problems can occur during initial start-up. They may be indicated by:

    • DTA 018 - Frame-slip out-of-service limit
    • DTA 021 - Loss-of-frame-alignment for 3 seconds
    • DCH 1003 - D-channel MDL errors
    Confirm that the Meridian 1 PRI parameters correlate to the far-end parameters.

    Check the Clock Controller is enabled and locked.

    Confirm Alternate or CRC multiframe: E1 PRI Example.

    Cannot enable the PRI. Two reasons follow:

    1. The far end PRI is disabled, indicated by:

    • PRI 000 - PRI is responding
    • DTA 005 - Remote alarm occurred
    • DCH 1010 - DCHI is software disabled

    2. There is no 1.5 Mb/2Mb connection, indicated by:

    • PRI 000 - PRI is responding
    • DTA 021 - Loss of frame alignment for 3 seconds
    • DCH 1010 - DCHI is software disabled
    Verify the circuit is connected, and enabled at the far-end.
    Meridian 1 initializes and there are no active B-channels. When a PRI or ISL trunk interfaces with another Meridian 1 and the Meridian 1 initializes, you may have to disable and then re-enable each B-channel.

    D Channel status:

    D Channel status is found in LD 96 with STAT DCH x.
    If x is not entered, the status of all D- channels is output. The output format is:

    DCH x : <Application_status> <Link_status> AUTO XX

    Where:

    Application status:
    APRIAwaiting PRI response
    CPRIChecking PRI
    DIAGapplication has failed
    DSBLapplication is disabled
    OPERlink is operational
    RSTapplication is in reset state
    SDCHSetting D-channel
    Link status:
    AESTAwaiting establishment
    ARLSAwaiting release
    EST ACTVDCH link is established and active
    EST STBYDCH link is established and is the standby
    FAILCH link has failed
    RESTrequest establishment
    RLSDCH link is released
    RSTDCH link is in reset state
    TSTTest mode
    AUTOif auto-recovery is enabled
    XXBKUP x / PRIM x (associated primary or backup DCH)
    DES :the DCH circuit designator follows

    For example:

    >ld 96
    DCH000
    .stat dch
    DCH 05 : DSBL  RST         AUTO  DES : E1_DID   <- this is down!
    DCH 06 : OPER  EST   ACTV  AUTO  DES : E1_TIE   <- this is good!
    

    NTAK79/NTBK50 Self-Test

    A self-test is performed when the card is inserted, or manually invoked with SLFT L, or SLFT L CH (loop, channel), in LD 60.

    CodeAssociated error
    0Self-test passed.
    1Self-test general failure.
    2LCAs failed to program correctly.
    38031 code checksum failure.
    48031 internal RAM failure.
    58031 external RAM failure.
    6PAD RAM failure.
    7AO7 signaling interface failure.
    8UART (card LAN) failure.
    CodeAssociated error
    9CEPT transceiver failure.
    10Line interface failure.
    11Receiver framing failure.
    12Transmit/receive (inter)national bit failure.
    13Yellow (remote) alarm failure.
    14PCM path integrity failure.
    15Loop remote loopback failure.
    16Channel remote loopback failure.
    .disl 104                    - you must disable the loop to run the self-test
    .slft 104                    - run the self-test procedure on card for loop 104
    
    SLFT OK                      - Passed, or a DTA105 L X error is returned
    .
    XMI002 24  0 2  PRI2         - after a self- test, the card is returned to service
    
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