omain interconnect requires translation. Tunnelling cannot solve the problem in the case of end-to-end incompatibility Understanding Changing Telecommunications - Building a Successful Telecom Business done at PDP context activation. The GGSN can either allocate the IP addresses itself, or interact with a RADIUS server for end-user authentication and retrieval of IP addresses. For this purpose, the GGSN includes a RADIUS client. Dynamic address allocation is done from a common pool of addresses. Seen from the IP domain (Internet or intranet) the terminal is addressed with an IP address. In reality, on the air interface the terminal is addressed with a temporary address based on the international mobile subscriber identity (IMSI). An address translation function in GGSN handles the IP address to IMSI address translation for the IP packets received from the external network addressed to a terminal. Routing within WCDMA/UMTS is based on IP numbers. Send packets already have an IP address for routing. The SGSN (serving GPRS support node) server functionality for session management is responsible for establishment, maintenance and release of end-user PDP contexts. This includes interworking with the GGSN for address allocation if dynamic IP addresses are used. The SGSN server supports the standardized interface to the HLR for management of end-user subscriber data such as IMSI, QoS profile and access point names. 8.10 TRAFFIC CASES The traffic cases presented here are simplified. The text below describes an early UMTS traffic case version. It is not the traffic case in itself that is important, instead the case exemplifies the management of the fundamental plans in a call, such as numbering, secu- rity, QoS, signalling and routing. An important task is to compose the packets accordingly, also adding appropriate low layer protocols. The description uses the term termination establishment. A termination is a number of user plane protocols necessary to establish in a node, typically in a media gateway. The packet design 