 MSC server functionality uses the internal clear codes in the end of selection analysis to actuate control plane routing. Routing Attribute Analysis Routing based on cell-dependent routing category functionality provides a tool to manage the local routing of the calls within one MGW. The cell-dependent routing category can be used in each different attribute Core Network Planning and Optimisation DIGITS ANALYSIS TREE DIGIT ANALYSIS CHARGING ORIGIN DESTINATION Succeeding UPDR for CHARGING User Plane DESTINATION ANALYSIS Analyses CHARGING Route ANNOUNCE SERVICE SPECIAL Control Plane ROUTE ROUTE CHARGING SPECIFIER max. 8 max. 8 BICC/SIP CIRCUIT GROUP ANNOUNCEMENTS - GSM END max. 4096 - HLR ENQUIRY - DDA (USUALLY PAD) Call Instance HUNTING - HANDOVER Codes in IN CALL GROUP BICC case - NUMBER max. 4096 MODIFICATION Preceding UPDR for User Plane CIRCUITS Analyses Figure 4.30 Digit analyses in MSS (DDA, direct data access; PAD, packet assembler/disassembler) analysis as an attribute. For example, all calls originating from certain cells to the PSTN may always need be routed to the nearest PSTN interconnection, but with no restrictions applying to calls towards other mobile subscribers. In such a configuration, the suitable cell-dependent routing (CDR) category attribute can be configured to the cells belonging to the BSC/RNC, which are physically connected to MGW1. The same category value is then analsed in the routing attribute analysis which gives the suitable tree as a result, e.g. 91. This tree 91 has analyses for both roaming numbers as well as PSTN numbers. Digit analysis of the PSTN numbers will lead to the route (and circuit group) containing the circuits that are present in the same MGW1. 4.6.2 Routing Components of the MSC Server The routing framework in the MSS is shown in Figure 4.30. 4.6.3 User Plane Routing User plane routing is responsible for controlling the user plane transmission in the MSS in a network where media processing is distributed to several MGWs (see Figure 4.31). In general, the user plane