e TeS server CS SIPServer IMS Connectivity network Packet backbone Corporate Internet WLAN hot spot GSM/GPRS/EDGE PSTN/ISDN GERAN Cable UTRAN fixed wireless access Figure 3.19 A server-rich target network where all new media industry-based applications can be distributed to many access networks/different users Layering and functional split can be achieved in many ways, usually based on some kind of layered architecture model (OSI, TCP/IP). The development is also a matter of convergence as described earlier in this chapter. Relationships between business, network design and management are further elaborated in Chapter 4. The architecture will be further explained in this chapter, with the con- cepts of network, convergence, layering, stratification and fundamental technical plans as pedagogical cornerstones. A network architecture for all types of accesses could look like Figure 3.18, assuming a significant legacy of circuit-mode voice services. Here media gateway controllers are needed in the control layer for the signalling for all the service access types supported. The IP multimedia system could eventually control all services from wherever they are accessed (home, work, visited location) or over whatever access (fixed broadband, digital TV, WCDMA, WLAN etc.). The new architecture is very server rich. See Figure 3.19. The control layer and the ser- vice layer are typically built up by servers. Server overviews are presented in Chapters 8, 9 and 14. 3.6 FUNDAMENTAL PLANS 3.6.1 TARGET - PROBLEM The general goal is to build a network that produces the desired services with sufficient end-to-end QoS and security at lowest cost. This may not sound overwhelmingly diffi- cult. However, in a time of transition there will be many interconnection points between technologies and between actors, both vertically and horizontally. The weakest link will decide the overall quality and security. Understanding Changing Telecommunications - Building a Successful Telecom Business All nodes must be programmed according to require