nhanced security (Enhanced because of multimedia) Enhanced charging (Enhanced because of multimedia) Supplementary services Note that the streaming multimedia (e.g. video streaming) can be transparent to the core network, i.e. no call session server is needed. What are 'Web Services'? Web services are briefly explained in Section 3.13. A more detailed explanation is given in Appendix 1. Services 5.1.4 HISTORY AND SUCCESS FACTORS History Historically voice services have been the main source of telecom income. Even if the data traffic is larger today, globally, voice income is still at least equal because of the different charging methods between voice and data. Since fixed and mobile voice is maturing in many countries, the development of the telecom sector will depend more and more on non-voice services or enhanced voice services including multimedia. Long-term forecasting of service (phone calls) development is another historical feature. It goes without saying that this is more or less impossible in a multiple service environment with considerable uncertainty about the market for individual services. Success Factors: Network In this less predictable situation the main tool, that is to say the network, must permit flexibility and agility to respond to the actual development. This is a main reason for the 'horizontal network'. In addition there is an increased need for flexibility in the connected terminals, which leads to a development where services are downloaded to the terminals. This does not mean that the actors can ignore their services once they can provide a large flexibility. With a good 'service feeling' and professional marketing the actors can increase their market share. And the network is by no means self-adaptive to the actual service load. On the contrary, service control becomes a matter for terminals well as the network. This is because the services entail a number of attributes. Service implementation is treated in Chapter 8. A specific success factor in the network is the introduction of a se