The present document specifies the Test Suite Structure and Test Purposes (TSSTP) for NGN/IMS interconnection tests at the Ic Interface to verify the overall compatibility of SIP@ ISDN and non-ISDN (PSTN) over the national or international NGN networks under consideration of the use of End Devices in the relevant networks (recommended by the network operator). The TSSTP specification covers the procedures described in TS 124 229 [2] and TS 129 165 [1] respectively. The specified Test Purposes are the basis for bilateral tests between national or international network operators. Even if tests between network operators is agreed@ exactly the test purposes defined in the current document are be performed. Modification of the requirements as described in TS 124 229 [2] and TS 129 165 [1] based on national requirements needs additional Test Purposes not described in the present document. This additional test may be defined and agreed between the test staff of the network operators.