This Recommendation specifies the architecture and requirements for the automatic switched transport network as applicable to SDH transport networks, as defined in ITU-T Rec. G.803, and Optical Transport Networks, as defined in ITU-T Rec. G.872. This Recommendation describes the set of control plane components that are used to manipulate transport network resources in order to provide the functionality of setting up, maintaining and releasing connections. The use of components allows for the separation of call control from connection control and the separation of routing and signalling. For the purposes of this Recommendation, components are used to represent abstract entities rather than instances of implementable software. UML-like notation is used to describe components of the architecture of the Automatically Switched Optical Network.