As the digital representation of an object of interest with data connections that enable convergence between the physical and digital states at an appropriate rate of synchronization. Digital twin federation is operations among one or more digital twin initiated to solve the problem crossing the boundaries of multiple domains. Recommendation ITU-T Y.4224 defines the requirements for digital twin federation. Based on the requirements, this Recommendation addresses the reference architecture of digital twin federation. This Recommendation defines the functionalities of each entity and the interfaces among the entities. In addition, this Recommendation also addresses operational flows of digital twin federation in different scenarios.