The scope of this Technical Specification is to provide a detailed specification for interworking between the A interface protocol and the Mobile Application Part for handling of supplementary services. The MAP interfaces of interest are the B-, C-, D- and E-interfaces. The A-, C-, D- and E-interfaces are physical interfaces while the B-interface is an internal interface defined for modelling purposes. Information relating to the modelling interface is not normative in this specification. Supplementary service signalling may be passed by the MSC/VLR between the A- and E-interfaces after inter-MSC handover. This procedure is transparent as far as supplementary services are concerned therefore interworking concerning this process is not described in this specification. Section 2 describes general procedures for interworking between the A- and D- physical interfaces. Section 3 describes the general procedures for the SS version negotiation. Section 4 describes the mapping of layer 3 radio path messages with Transaction Capabilities (TC) transaction sublayer messages for interworking between the A- and D- physical interfaces. Section 5 describes specific interworking procedures for all interfaces relating to call related SS activity. Section 6 describes specific interworking procedures for all interfaces relating to call independent SS activity. Section 6 also covers the interworking between the MAP User (see TS GSM 09.02) and the SS handling functions of the network entities (see TS GSM 04.10 and TS GSM 04.80).