erion under which trouble tickets need to be created. Also the system might take additional action automatically such as paging an operator or triggering a re-route of customer service based on defined rules. Again the open nature of the NGN OSS will allow these sophisticated fault management services to be developed and deployed. The Ultimate Guide to Building and Delivering OSS/BSS Service Order Manager/ Workflow Manager Logical Integrated Assign NMS Database Inter-Domain Service Provisioning Order Resources Inter-Domain Manager Assign Intra-Domain Request for Domain Resources Provisioning Domain Manager Domain Manager Domain Manager Request for Element Provisioning Configuration Commands Connections Core IP and Provisioned Optical Access Through Transport Domains Switching Figure 43. Fault Management Framework for the Next Generation 3.2 QoS and SLA Management QoS is defined as a measure of the service quality provided to a customer. Circuit switched networks utilize dedicated connections to support delivery of service. They provide high quality of service since the entire connection bandwidth is dedicated to the session. On the other hand, IP, a leading technology for next-generation networks, allows multiple sessions to share the same network path hence provides better network utilization but no guarantees of service quality. Since IP is fast becoming the backbone technology of choice, service providers must be able to deploy and manage QoS-enabled services using IP. Protocols such as DiffServ and RSVP allow prioritization of traffic on an IP network using quality of service parameters. New standards such as MPLS and VPN also allow delivery of differentiated service over an IP core. Based on varying QoS levels, service providers establish Service Level Agreements Chapter 8 - Next-Generation OSS (SLAs) with the customer, often charging premium prices for stringent SLAs. In order to take advantage of the network evolution in IP, NGN OSSs must be able to initially provision tiered QoS services on the network, b