The present document defines the stage 2 description for the SIP-I based CS core network. The logical architecture for the SIP-I based CS core network is defined in TS 23.205. This stage 2 shall cover the information flows between the GMSC server, MSC server and media gateways that are required to support a SIP-I based Nc interface. Note that nothing in the present document shall preclude an implementation of a combined MSC Server and MGW. The present document shall show the CS core network termination of the Iu and A interfaces in order to cover the information flow stimulus to the core network and describe the interaction with the supplementary and value added services and capabilities. For the purposes of the present document, the Nc interface profile is based on ITU-T Q.1912.5 [9] SIP-I profile C and is specified in TS 29.231. The Mc interface profile is based on ITU-T H.248.1 [5] and is specified in TS 29.232. Local Call Local Switch (LCLS) functionality is further specified in TS 23.284. The present document is applicable only for IP transport in the CS core network. Details of Transcoder-Free Operation/Out of Band Transcoder Control are outside the scope of the present document. See TS 23.153 for more information. The present document specifies functions, procedures and information which apply to GERAN Iu mode. However, functionality related to GERAN Iu mode is neither maintained nor enhanced.

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