The specifications of the sections of IEC 1334-4 apply to the communication through the socalled distribution line carrier technology (DLC) on both low and medium voltage distribution networks. The application range based on telecommunication processes is wide and cannot be described exhaustively in this section; application examples are: control and monitoring of the distribution network, order broadcast, control of user interfaces, public lighting, traffic lights supervision, automatic meter reading, etc. This section of IEC 1334-4 describes the rules used to design an application service element, the ISO connectionless ACSE, and the DLMS Application Service Element. Extensions to other communication media are also allowed. The mapping of the DLMS services is based on the three-layer stack. Future extensions to stacks of more than three layers are possible and may use the rules described in this section. In such a case, the DLMS interface with the underlying layers should be remapped to the new one: the specification of the mapping criteria will be dealt with in corresponding appendices, in respect of the rules defined in this section