Recommendation ITU-T G.7702 describes the reference architecture for software defined networking (SDN) control of transport networks applicable to both connection-oriented circuit and/or packet transport networks. This architecture is described in terms of abstract components and interfaces that represent logical functions (abstract entities versus physical implementations). Amendment 1 describes the name space, resource and component distribution within one SDN controller, and aligns with the clause structure in Recommendation ITU-T G.7701. Amendment 2 provides guidance on how key concepts and functions of specific interfaces could be applied to the Control Plane Interface (CPI).