P configuration. Signalling User and Application Parts When the lower SS7 layer components (links, link sets, route and route sets) are created, it is possible to define the higher layer SS7 user and application parts. The following issues should be taken into consideration when planning the SS7 signalling network. Use of Signalling Gateways The MSS without any non-IP signalling connections and with M3UA signalling connections requires the presence of the signalling gateway network element. In the MSS concept such functionality can be realised by the MGW (alternatively in an STP or SRRi, or signalling routing register). Signalling gateways terminate narrowband and broadband signalling link sets and act as STPs for traffic towards the MSS network elements. The presence of a signalling gateway in the path between two signalling points in the MSS system is perceived as a normal STP. The signalling routing configurations are therefore similar to routes with a signalling gateway as the STP. Use of M3UA (MTP3 User Adaptation) M3UA is used to transport SS7 signalling traffic over SCTP/IP interfaces. The MSS allows the use of M3UA with the same signalling user parts as in TDM signalling links. Configuration of these IP signalling routes is similar to the configuration of PCM based signalling links. Configuring SCCP in MSS The MSS can transport the SCCP user part over either IP or TDM based signalling links. The configuration of both MTP3 and M3UA layers is very similar because both provide a similar interface to the SCCP. The SCCP is configured in the MSS for the following application parts: MAP traffic BSSAP traffic RANAP traffic IN traffic (INAP/CAP) ISDN supplementary services (SSAP) SCCP level STP traffic towards other signalling points In the example presented in Figure 4.27, a possible configuration of the SCCP between the RNC is connected through the Iu-CS interface to MGW1. In this example, MGW1 acts as an STP for RANAP signalling which terminates in the MSS. An IP signalling link set is created between the MSS a