The present document specifies the user Abstract Test Suite (ATS) for the TB reference point or coincident SB and TB
reference point (as defined in ITU-T Recommendation I.413 [9]) of implementations conforming to the standards for the signalling user-network layer 3 specification for ATM traffic descriptor modification with negotiation by the connection owner of the Digital Subscriber Signalling System No. two (DSS2) protocol for the pan-European Broadband Integrated Services Digital Network (B-ISDN), EN 301 486-1 [1]. A further part of the present document specifies the Test Suite Structure and Test Purposes (TSS&TP) related to this ATS and partial PIXIT proforma. Other parts specify the TSS&TP and the ATS and partial PIXIT proforma for the Network side of the TB reference point or coincident SB and TB reference point of implementations conforming to EN 301 486-1 [1].