1. A network management system ( 100 ) for identifying and accessing Quality of Service, QoS, issues within a communications network ( 104 , 106 ), the network management system comprising: a service performance unit ( 108 ) that (1) captures traffic, and performance related data on interfaces in the communications network and at nodes in the communications network, (2) formats the captured traffic and performance related data into service usage transactions each including an identification field and a factor, Where the factor describes an aspect of the communications network when the corresponding service usage transaction has taken place, and (3) correlates the individual service usage transactions based on the identification fields to create service performance records ( 206 ) each including one of the identification fields, multiple factors, and a service quality metric; a service performance database ( 110 ), coupled to the service performance unit, is that stores the service performance records; a factor scoring system ( 112 ), coupled to the service performance database, that computes a score for each factor in each service performance record, where the score indicates an influence the corresponding factor has on the corresponding service quality metric; a factor score database ( 114 ), coupled to the factor scoring system, that stores the computed factor scores for each service performance record together with a reference to the corresponding service performance record; and a factor strength analysis module ( 116 ), coupled to the factor score database and the service performance database, that aggregates at least a subset of the service performance records together with the corresponding factor scores and uses a rule set to analyze the aggregated records to indicate a cause for a specific service quality degradation detected within the communications network.