E and the gateway node. Currently in IETF, inter-domain policy interactions are not defined. Towards IP Based Networks application IP Policy Resource servers Control Manager (e.g., local SIP proxy) UTRAN CN EDGE Gateway Ext. IP Netw. IP BS Manager IP BS Manager Ext. IP Service Control Adm./Cap Adm./Cap. Adm./Cap. Subsc. Adm./Cap. Transl. Control Control Control Control Control Transl. UMTS BS UMTS BS UMTS BS Manager Manager Manager Manager Radio BS- Radio BS lu BS lu BS CN BS CN BS Manager Manager Manager Manager Manager Manager lu NS lu NS BB NS BB NS ph. BS M ph. BS M Manager Manager Manager Manager protocol interface service primitive interface Figure 9.18 UMTS QoS management functions for control plane bearer service of an external IP server [7]. 9.9.2.4 Implementing QoS A practical solution would allow a UMTS operator or service provider to use standard- ized Internet QoS mechanisms across the IP core backbone network. GGSN/edge router function would connect to the IP backbone. These mechanisms would then afford the use of Service Level Agreements (SLAs) as a management tool to control resources of the IP core backbone network. The SLA would contain specifications on technical is- sues and administrative contractual information. The connection from the User Equipment (UE) to the remote terminal/server can be established over different network paths. The UE accesses UTRAN over Uu radio inter- face. Over the Iu PS interface UTRAN can, e.g. connect to the SGSN and multimedia gateway. The core IP backbone would transport the IP traffic between the SGSN and the GGSN (Gn interface) and between the GGSN and application servers in the opera- tor's service network or a border router to external Internet. For example, a subscriber flow for real time IP applications will use dedicated radio channels over Uu, and that the QoS through UMTS would be controlled per user flow in RNC, SGSN and GGSN nodes, respectively. The nodes would use the IP core backbone for IP based transport over Iu and Gn. For this transport QoS woul