 a call. 4.5.2 Control Plane Routing Implementation of the MSS routing configuration is split into two separate parts as a result of the split architecture of the MSS and MGW. These routing parts need to be configured before any user traffic can be carried in the release 4 network. Section user plane routing and analysis planning, described above, give the configurations used in user plane routing. The following sections will therefore describe the configuration of the control plane routing, including the following: configuring analyses; configuring UPD and UPDR; configuring SS7 signalling; configuring charging. The control plane routing is the highest level of routing configuration present in the MSS. Routing is done by analysing the dialled MSISDN of the subscriber, MSRN or other routable E.164 number. User plane routing is executed after finding the correct control plane destination for the call. Some results from the control plane routing level are used as input for user plane routing. Figure 4.29 represents an example logical hierarchy of the different routing levels in the MSS. Each box represents a certain analysis and a number indicates the order of the analysis. This should be presented earlier in order to understand the split between MGW analysis/routing and MSS analysis/routing before going into each of these in detail, as commented earlier. As there are two different routing layers instead of one layer currently in the MSC, it is the user plane destination reference (UPDR) that links these two layers together. Control plane routing consists of analysing the call control-related parameters, such as the different attributes available from signalling, the previous call control analysis and the received called party number. The main purpose of the call control analysis is to find the destination for the call, set the charging and execute tasks during the call establishment or at the end of the call. The UPDR parameter serves as a link between the separated control plane and user plane procedures. By confi