 Physical Communication Logical Communication Figure 3.33 A typical layered network Understanding Changing Telecommunications - Building a Successful Telecom Business As shown in Figure 3.33 the expression 'Network interface and hardware layer' can be used for underlying connectivity layers in IP stratification. A similar idea is used for tunnelling, a layering and stratification technique for pro- tection of data integrity and confidentiality in IP networks. Tunnels require 'extra' layers to encapsulate the often sensitive end-to-end user traffic. Tunnels are described in the Chapter 6. 3.10 THE CONTROL LAYER As seen in Figure 3.17 the control network will initially be more heterogeneous than other core layers. The present target control design is the IP multimedia subsystem, IMS, according to Figure 3.18. The control layer is further dealt with in Chapter 14. 3.11 THE SERVICE LAYER From the convergence point of view the service network has the most central position. See Figure 3.34. An obvious task becomes integrating contents with users, their terminal capabilities and the network capabilities. Another task is to successively support new sets of applications. The service layer role for service implementation is further dealt with in Chapter 8, and the service network itself is dealt with in Chapter 9. The service layer responds to a number of needs: Contents Needless to say, multimedia is an important requirement for content. The final receivers are the eye, the ear and the computer, which could be a mobile device. For mobile devices it should be possible to update the content according to posi- tion. Other changes of content may be synchronization of content with other terminals employed by the user. It might/should be possible to download applications to the terminal, in order to offer new content. (Java, .NET). It should be possible to receive real-time, streamed or stored content. Client terminal Server Application control Applications Applications Service layer Positioning, MMS, WAP, kJava Service enabler