A computer implemented method to identify a call end associated with a problem that caused failure of an internet protocol-based call, the method comprising: accessing a first call detail record, CDR, set including at least one CDR associated with a first call end of the failed call; determining from the first CDR set indicators of failure attribution of the failed call; determining whether fault for failure of the failed call is attributed to the first call end based on the indicators of failure attribution; outputting an indication that the fault is attributed to the first call end if it was determined that the fault is attributed to the first call end; outputting the indication to indicate the first call end is acquitted of the fault if it was determined the fault is not attributed to the first call end; accessing a second CDR set including at least one CDR associated with a second call end of the failed call; correlating the first and second CDR sets as being associated with the failed call; determining from the second CDR set indicators of failure attribution of the failed call; determining whether fault is attributed to the first call end or the second call end based on the indicators of failure attribution associated with the first and second CDR sets; outputting an indication of one of the first and second call ends of the two first and second call ends determined to be attributed with the fault for failure of the failed call; outputting an indication to indicate the other of the first and second call ends is acquitted of the fault for failure of the failed call; and accessing a configurable failure ranking, wherein determining whether the fault is attributed to the first call end or the second call end is further based on relative failure ranking of first and second cause codes included in the indicators of failure attribution. accessing a first call detail record, CDR, set including at least one CDR associated with a first call end of the failed call; determining from the first CDR set indicators of failure attribution of the failed call; determining whether fault for failure of the failed call is attributed to the first call end based on the indicators of failure attribution; outputting an indication that the fault is attributed to the first call end if it was determined that the fault is attributed to the first call end; outputting the indication to indicate the first call end is acquitted of the fault if it was determined the fault is not attributed to the first call end; accessing a second CDR set including at least one CDR associated with a second call end of the failed call; correlating the first and second CDR sets as being associated with the failed call; determining from the second CDR set indicators of failure attribution of the failed call; determining whether fault is attributed to the first call end or the second call end based on the indicators of failure attribution associated with the first and second CDR sets; outputting an indication of one of the first and second call ends of the two first and second call ends determined to be attributed with the fault for failure of the failed call; outputting an indication to indicate the other of the first and second call ends is acquitted of the fault for failure of the failed call; and accessing a configurable failure ranking, wherein determining whether the fault is attributed to the first call end or the second call end is further based on relative failure ranking of first and second cause codes included in the indicators of failure attribution.