Recommendation ITU-T Q.3941.1 specifies Network integration testing between SIP and ISDN/PSTN network. It is part 5 of a multi-part deliverable covering network integration testing between SIP and ISDN/PSTN network signalling protocols: Part 1: Test suite structure and test purposes for SIP-ISDN. Part 2: Abstract test suite and partial protocol implementation extra information for testing proforma specification for SIP-ISDN. Part 3: Test suite structure and test purposes for SIP-SIP. Part 4: Abstract test suite and partial protocol implementation extra information for testing proforma specification for SIP-SIP. Part 5: Test Suite Structure and Test Purposes (TSS&TP) for Network Integration Tests between ISDN-ISDN and ISDN-PSTN over SIP II NNI / SIP-I NNI. This Recommendation endorses ETSI TS 186 001-1 V3.1.1 (2015-11) Core Network and Interoperability Testing (INT); Network Integration Testing between SIP and ISDN/PSTN network signalling protocols; Part 1: Test Suite Structure and Test Purposes (TSS&TP) for SIP-ISDN