ITU Q.3941.1:2011 Network Integration Testing Between Sip And Isdn/Pstn Network Signalling Protocols - Part 1: Test Suite Structure And Test Purposes For Sip-Isdn Describes the test suite structure and test purposes (TSS&TP) for network integration testing to verify the overall compatibility of SIP, ISDN and non-ISDN (PSTN) over the national or international IS