uired and address portability Routing plan: Routing of incoming calls Routing and interconnection plan: Cooperation with BGCF (border gateway control function) for calls to the PSTN to determine the MGCF (media gateway control func- tion) to use Transmission/QoS plan: Analysis of need for a transcoder for mobile to mobile calls Switching plan: Controlling the MRF in order to support need for multi-party calls Billing Telecom business Service Service Service, security, QoS Service layer management Dimensioning Numbering Charging Routing Signalling Control layer Dependability Mobility management Switching Frequency Transmission Traffic resources Organization Synchronization in connectivity layer Figure 14.4 Security and QoS are also part of the control network and its tasks Control Network Charging: (and security) plan: Call monitoring and logging for billing, verification, auditing, intercept or other purpose Security plan: Is the requested outgoing communication allowed given the current subscription? QoS: Authorize the bearer resources for the appropriate QoS level. Determination of allowed QoS classes is done by means of subscriber profile information At the end of the chapter the distribution of functionality to the numerous individual nodes will be treated at an overview level. Let us have a very brief look at some specific FP features or references concerning the control layer. 14.3.1 SIGNALLING Signaling is a focal point in this chapter. See Section 14.4. 14.3.2 MOBILITY MANAGEMENT: ROAMING Roaming between GSM and UMTS is one of the important tasks, where the control layer is involved. The inter-system roaming solution allows the subscriber to roam from the UMTS net- work to the GSM network and vice versa. The MSC Server supports mobility management in order to enable attachment/detachment and roaming within the UMTS network, between UMTS networks, and between UMTS and GSM networks. See more in Chapter 15. 14.3.3 MOBILITY MANAGEMENT: HANDOVER The MSC server supports inter-MSC and intra-MSC handover from UMT