The paper describes the application of SDL-92[1] and OMT[2] to the design of a V5.x Access Network interface. While OMT is used to model the management aspects of the system, typically described as TMN objects, SDL-92 is used to describe the V5 signalling stack as well as all the distributed components. The resultant combined model is used to automatically produce an efficient C++ implementation. TTCN is the language used to evaluate the conformance of the V5 interface standards. However, complementar and service oriented testing is also required. Service provision correctness, service interaction avoidance and, particularly, quality of the services, need characterisation. For that, MSC and SDL combined languages complemented with time and probabilistic descriptions, are being used to specify test purposes, describe and verify test cases. Keywords V5 interface, testing, automata, QOS, SDL, OMT, MSC, TTCN.