indication of the impact on the customer. Thinking in this way leads to the obvious question of why operators manage their networks primarily on network events. Even performance management data give more information on the performance of an individual network component than they do about the performance of the end-to-end service delivery. Of course, no one would suggest that an operator should ignore the alarms generated by network components any more than a driver should ignore the oil warning light. But surely the emphasis must, metaphorically, be to look out of the window to ensure some depth of awareness of customer experience. The findings of the TMF's SQM catalyst project highlighted the need to find more effective ways of managing service quality. It found that this could be achieved by collecting data from multiple sources and aggregating them to provide an overall quality measurement. The project then proved the concept by aggregating alarms, performance statistics, Call Detail Records (CDRs) and application event logs. Figure 7.5 presents an example of how end-to-end QoS may be measured for a service. This may be done by breaking a service down into service components, each OSS for Telecom Networks End-to-End Mobile Access Transport Network Network SLA RADIUS Firewall Radius GPRS/UMTS ISP IT IP Transport Mobile Access Network Network Domain Domain Domain Diff-Serv MPLS-TE Diff-Serv Diff-Serv Mobile Network IP Transport IT Network Application Service Access Service Service Access Service Access Point Access Point Point Point (SP BTS) (SP GGSN) (ISP IP Router) (ISP E-mail Server) Figure 7.5 End-to-end QoS. of which may have one or several internal SLAs associated with it. The combination of the SLAs that are internal to an end-to-end process flow provides a measurement of the totality of a service, and hence gives an indication of customer experience. The diagram presents a granular approach that is not always appreciated in SLM discussions. This level of granularity is not even offered in all SLM systems