ent) previously negotiated, operating respectively at the net- work level and at the service level. On the other hand, service providers should be able to keep track of the services being used by their customers, both inside their own network and while roaming. The multiple network functions can then be listed as: physically supporting the mobility of the terminals and multiple technologies; guaranteeing planned QoS levels to specific traffic flows; supporting interoperator information interchange for multiple-operator service provision; realising appropriate monitoring functions for providing information to the service operator about network and service usage; implementing confidentiality both on user traffic and on network control information; entities involved in the architecture. All-IP Network QoS Broker AAAC System 802.11 Domain Access Router WCDMA to WCDMA WCDMA to 802.11 Intra domain Intra domain WCDMA 802.11 to WCDMA Domain Inter domant WCDMA 802.1) to 802.11 802.11 Inter domain 802.11 802.11 WCDMA 802.11 802.11 to WCDMA Domain 802.11 WCDMA to Ethemet Inter domain Intra domain Figure 5.8 Conceptual diagram of a 4G network The two main entities considered in this architecture are: the user, a person with a service level agreement (SLA) for a set of services; the network operator, who owns the administrative network domain, thereby providing the transfer of information across end points. Conceptual Network Architecture A conceptual layout of a 4G network is shown in Figure 5.8, illustrating some of the handover possibilities during user movement. There are basically three administrative domains in the figure, each using different types of access technologies. Each administrative domain contains: an AAAC system; at least one network access control entity; the QoS broker (QoSB). From the diagram it is observed that the major entities involved in the architecture are: mobile terminal (MT): the user terminal from where the user accesses the subscribed services; access router (AR): the MT point of attachment to