A telecommunication network is a complex network which can be described in a number of different ways depending on the particular purpose of the description. This Recommendation describes the network as a transport network from the viewpoint of the information transfer capability. This Recommendation provides a set of constructs (definitions and diagrammatic symbols) and the semantics that can be used to describe such a viewpoint. A transport network transfers user information from a sender at one location to a receiver at another location. A transport network can also transfer various kinds of network control information such as signalling@ and operations and maintenance information for the control functional group. This Recommendation describes the functional architecture of transport networks in a technology-independent way. The generic functional architecture of transport networks provides the basis for a harmonized set of functional architecture Recommendations for specific layer network technologies@ including those that use connection-oriented circuit switching (commonly referred to as CO-CS) or connection-oriented packet switching (commonly referred to as CO-PS)@ and connectionless packet switching (commonly referred to as CL-PS)@ and a corresponding set of Recommendations for management@ performance analysis@ and equipment specifications. This Recommendation provides the definition of the architectural constructs that are required to describe a transport network. The theoretical material that was used as the basis for these definitions is provided in Annex A (concepts)@ Annex B (properties of systems)@ and Annex C (properties of communications).