ng, a future trend. Having talked about services the next step is to discuss networks. This term will be defined (for the book) at the beginning of the network-oriented chapter (Chapter 3). 3G and next generation networks (NGN) are specific network solutions. The book objective Clients Application control, e.g. browser Content Service Server Other resources User interface Common Application Business resources (SW components) Firewall logic Application interface Terminal located Service capability 2 Service enablers Service capability 1 Service enablers The network domain (UMTS, GSM, PSTN/ISDN etc) Figure 1.13 An overall picture of an application and its relation to a service offered by application and its support functions Understanding Changing Telecommunications - Building a Successful Telecom Business to be general and holistic favours other expressions such as 'all-access networks' and 'horizontal networks'. Therefore 3G and NGN are not used very much. Another common term is 'broadband'. How broad is broadband? Originally (ITU-T recommendation I.113) it was faster than primary rate ISDN (in Europe about 2 Mbit/s, in the USA about 1.5 Mbit/s). Nowadays network operators advertise broadband at 256 kbit/s and higher. FCC in the USA has chosen 200 kbit/s since this bit rate is considered sufficient for full-motion video and changing web pages as fast as one can flip through the pages of a book. The term 'enabler' may also cause interpretation problems. In this book it is used with a meaning close to 'new standards'. In the literature sometimes other interpretations can be observed, where enablers reside only in the service layer. To avoid misunderstanding the term service enabler is used in such a context. By 'service enabler' in this book we mean service supporting elements in the service network and the terminals. It embraces another tricky term, 'service capability servers' (SCS). An ETSI definition of SCS is 'a functional entity providing open systems architecture (OSA) interfaces for an application'. An SCS 