This Recommendation describes the functional architecture of connectionless layer networks using the methodology described in ITU-T Rec. G.805. The concept of the connection is central to the functional architecture described in ITU-T Rec. G.805 and in order to provide a common framework between the connection-oriented layer networks and a connectionless layer network, it is necessary to introduce new concepts that describe connectionless behaviour. The connectionless transport network functionality is described from a network level viewpoint, taking into account layer network structure, networking topology, client characteristic information, client/server layer associations and mapping between connectionless and connection-oriented layer networks.