Signalling in ATM networks: experiences with an object-oriented solution

Today the Asynchronous Transfer Mode (ATM) is extensively used on the level of public pilot networks. In the first stages of introduction these networks do not yet support signalling. However, the standardisation bodies ITU-TS (former CCITT) and ATM Forum have already produced first specifications for signalling in ATM networks. These specifications define the basic procedures for point-to-point signalling. Further specifications, that are now being defined, will enlarge this basic set to support fully signalling for multimedia applications between several users (point-to-multipoint). This signifies that developers of signalling software have to cope with two demands: Until a Recommendation for a specification is approved it undergoes constant change. The introduction of a new specification is associated with an enormous increase in software functionality. In this paper we show how an object-oriented solution allows the demands of flexibility and extendability robe satisfied. This solution consists of a set of classes that are put together to form a very flexible, extendable framework. This framework can be refined to realise any signalling protocol. We show how this framework was used to build an implementation of the ATM signalling protocol Q.2931 defined by ITU-TS. The reusability and flexibility of it was verified when the framework classes were integrated in the signalling architecture of an ATM switch. The framework was realised with object-oriented techniques and implemented in C++