An embodiment of the present invention relates to an operator management system in a first administrative domain for supporting a user roaming from the first administrative domain to a second administrative domain within a network architecture. The network architecture comprises a collection of interconnected network functions deployed in a control plane and a user plane, and the interconnected NFs comprise at least core network control plane functions and a core network user plane function. The OMS in the first administrative domain is configured to generate and issue to an OMS in the second administrative domain, a roaming management request for roaming a user from the first administrative domain to the second administrative domain, over an inter-operator management interface, and configured to instruct the OMS in the second administrative domain to configure the second administrative domain based on the roaming management request to support the user roaming.