A digital twin is a digital representation of an observable object with a data connection that enables convergence between the physical state and digital state at an appropriate synchronization rate. Digital twins have been applied in various industry domains, including manufacturing, transportation, energy, firefighting, healthcare, and safety. Digital twin federation is the act of sharing application context among two or more digital twins to solve problems that involve multiple domains. For the digital twin federation, signalling requirements need to be defined among relevant entities, such as digital twins, a registry and a communication adaptor. These requirements can be used as a basis for designing signaling protocols among the relevant entities. This Recommendation defines the signalling requirements for digital twin federation over managed peer-to-peer communications.