MSC Server Server Server SCS = Service capability server Access Core connectivity SCP = Service Corresponds to control point IN network intelligence control network in the CS1 (+) new network Switch with SSP = Service control part switching point Figure 3.39 A distributed view External UMTS/GPRS network UTRAN backbone TCP/UDP TCP/UDP Relay Relay GTP-U GTP-U GTP-U GTP-U L2/L1 L2/L1 L2/L1 L2/L1 lu-Ps Gn/Gp User level IP Transport level IP IPv6 in UMTS Figure 3.40 Example of server connection. The IP service network is normally on top of the core network SGSN-GGSN the other, that is to say gateways. The gateways tend to attain a key 'spider' role in many types of networks. The gateways are also denoted edge nodes and interworking nodes. The nodes enable a successive migration from the networks of today to the horizontal network. A typical situation is the combination traditional 'vertical' access and horizontal Networks and Technologies Terminal Other network if any Service network, if any Content Content Applications Service enablers Service enablers Network control and intelligence Access Core connectivity User information flow The reference model network segmentation Figure 3.41 The server inserted at the 'outer' edge node MANAGEMENT CONTROL FUNCTION FUNCTION Management Control network Trunk network Trunk Trunk Terminal Terminal Terminal Terminal Terminal Traffic resources Figure 3.42 A network element based view of a horizontal network. The control parts have now been split from the nodes and located in a control network core. In UMTS the opposite is foreseen during an initial period, until the core upgrade can catch up with the new layered access in UMTS. Of course the new network can also be described by means of a network element ori- ented view. See Figure 3.42, which gives an example. We leave to the reader to conclude what view fits the horizontal network best. The new network is sometimes called the next generation network (NGN), when talking about network architectures in this book. 3.12.2 THE BANDWIDTH 