Như minh họa trong hình , GGSN bắt đầu mạng được yêu cầu kích hoạt ngữ cảnh PDP bằng cách gửi một tin nhắn Send-định tuyến thông tin cho GPRS HLR để lấy địa chỉ của SGSN phục vụ điện thoại di động đích. Thông báo này mang IMSI của điện thoại di động, mà sẽ được sử dụng | 108 WIRELESS IP NETWORK ARCHITECTURES Fig. MWIF-layered functional architecture management communication session management resource management address management authentication and accounting functions. Service Layer The service layer provides service control functions for 1 services provided to the end users and 2 services needed by the network to make effective use of the lower functional layers. The service layer contains for example control logics for services provided to the users applications provided to the users directory and name servers location servers policy servers and authentication and authorization servers. Application Layer The application layer is composed of third-party applications and services provided to the users. The application layer may interact with any lower functional layer directly without having to go through the intermediate functional layers. A third-party refers to a provider that is not the owner of the other three functional layers. The security and the OAM P Operation Administration Maintenance and Provisioning functions may span across multiple functional layers. The OAM P functions are responsible for ensuring proper operation and maintenance of network transport control and service infrastructure. Main OAM P functionality includes network provisioning network configuration management fault management performance management and billing functions. MWIF ALL-IP MOBILE NETWORKS 109 The layered functional architecture reflects the design principle of separation of concerns. In particular control and user traffic transport are logically separated. Within the control layer session management and mobility are also logically separated. Service control is also logically separated from session management and data transport. Figure illustrates the network reference architecture that shows the main functional entities and their interactions 41 . An access network provides radio connectivity to enable a mobile to gain radio .
