H.320 etc.) Media format (e.g. for video, H.261 or MPEG, etc.) Information on how to receive media (e.g. address, port, format etc.) Period of time the session is active SIP and SDP are described in more detail in Chapter 14. From Figure 3.39 and Figure 3.41, the terminal devices and the service network are at the top. The connectivity is split into access and core connectivity, since there are SO many access types. On top of the backbone there is a control network. In the border access backbone an edge node is inserted. On the border to another operator another edge node is inserted. This distributed view is very useful to show particular implementations, in Figure 3.39 a future IN implementation. Although IN basically belongs to the control layer, it can be implemented like an application with application logic = IN logic, a net- work resource gateway, service capability servers from the service layer, and suitable inter- faces according to the figure. The control servers are the controlled elements in this case. The server in Figure 3.40 belongs to another network. An 'own' server should be included, but it is not very easy to find a good position. As an example it could be inserted close to the edge node to other operators. See Figures 3.41 and 3.42. The present situation with quite a number of networks in operation is a kind of nightmare for the operators. And more networks are appearing. WLAN is already fairly widespread and 3G appears on the mobile side. The number and possible types of intercon- nection between different networks become quite large. This situation generates a need for network elements with one network interface on one side and another network interface on Understanding Changing Telecommunications - Building a Successful Telecom Business Upper part: New implementation of IN services. Lower part: Traditional implementation in vertical networks Terminal if any Other network IN service logic Applications API (Parlay, OSA) NRG SCS NRG = Network resource gateway MAP, CS1(+) Firewall MSC, TeS, G