The purpose of the present document is to present and describe issues and design choices made to support IPv6 into the generic test adapter and codec suited for TTCN-3 interoperability testing within STF370@ STF407 and STF435. NOTE: Both client and server were concerned by supporting of IPv6. For further information@ the reader is referred to EG 202 810 [i.2] for global view of methodology and framework for automated interoperability testing and TR 102 788 [i.3] for an overall view of the IMS interoperability test architecture which has served as the main source for design requirements. The present document has been written with the assumption that the reader is well versed in C++ and TTCN-3 (ES 201 873-1 [i.1]) programming. Also good knowledge of the operation of ES 201 873-5 [i.7] and ES 201 873-6 [i.8] standards is assumed.