lecommunications - Building a Successful Telecom Business, by A. Olsson © 2003 Ericsson och Student litteratur. ISBN: 0-470-86851-1 Understanding Changing Telecommunications - Building a Successful Telecom Business Regarding intelligence, the traditional IN SCP nodes are part of the control layer, assisting the control servers. In addition, IN based control functions are- or will- be implemented in the service layer, See for example Figure 8.7 in Chapter 8. Much traffic can manage without the control layer. Connectionless best effort IP traffic is a good example, leased lines is another. As indicated in Chapter 12, there is an internal control function in the connectivity layer as well, serving data oriented traffic in IP, ATM and other networks. Both ordinary voice and data communication have managed without a service layer, but this will change with an increasing number of service offerings beyond voice. The development will increase the business role of the service layer. The control layer and the connectivity layer will serve the service layer more and more by means of APIs. For interconnected networks see Chapter 15. The control layer is related to MGW/edge node control (See Figure 14.1). There isn't normally a 1:1 relation between edge nodes/MGW:s and media gateway control nodes/control functions, unless the nodes are built in one physical unit. Figure 11.7 gives a better perception. However, GGSN and releases of SGSN and other nodes are typically implemented in one physical unit. In homogeneous environments there is no need for gateway, see for example Figure 14.5. Figure 14.2 shows a number of control parts or domains in the control layer, the common home subscriber server (HSS) function and a signalling gateway server function. The signalling traffic gateway is, strictly speaking, part of the connectivity layer. The description of control in this chapter covers control of the following domains of networks: Access transport Access transport = Optical rings Control network used when applicable Service laye