take client and server roles. A client-server scenario can be described according to Figure 5.20. Between the servers and end users are the various service provider roles. It should be noted that services used to be offered without a service network. The advantages with such a network are explained in the Chapter 9. The services have to rely on the underlying network for the 'find and connect functions', security and end-to-end transfer quality. The implementation could at least partly be illustrated by means of a game called ABC. See Figure 5.21. Obviously the game uses WAP and UMTS or GPRS. The clients need colour displays. 5.12.1 THE OVERALL BUSINESS VIEW OF THE HORIZONTAL NETWORK See Figure 5.22 for a business view of the horizontal network. Every architecture needs a competitive service-oriented edge to become implemented and survive. That makes it possible to explain the new network architecture from a business point of view. The various features indicated in the figure will be explained in the following chapters. The various network parts will be described in more depth in other chapters. 5.13 THE CORE NETWORK AND THE SERVICE PLAN The ideal core should satisfy both tele-centric and data-centric operators. For established voice operators, the most debated area when entering the horizontal way of building net- works is IP versus ATM as a bearer in the packet backbone. See for example Figure 5.23. A third possibility is gaining ground: multi protocol label switching (MPLS). MPLS employs both IP and ATM techniques (or IP and other layer 2 technologies). The bearer issue including the MPLS solution will be handled in more detail in Chapters 8 and 12. ROCE-based business objectives applied on the core may look like Figure 5.24, which shows some relevant considerations when selecting transport technology to support the business plan. In principle the core/backbone network must be able to offer a high QoS that is the same for short and long distances. Most of the permitted bit error rates and other degra- dations 