With the increasing deployment of 5G Non-public Networks, the telco environment is becoming massively multi-administrated with a wide range of full networks deployed close and covering only the use case area. To benefit the most of this, a roaming solution must be set in place enabling devices to safely communicate using visited infrastructures either with local service or with the ones from the home networks. As a first step in this direction, this article proposes a new architecture for Non-public Networks roaming, stemming from the 3GPP 5G macro-operator roaming and adapted to the specifics of the communication for geographically-distant, small networks interconnected by third party unreliable backhauls. Furthermore, the architecture is exemplified, and its potential is evaluated as further extensions to the Fraunhofer FOKUS Open5GCore, showing that it outperforms today's roaming solution in terms of flexibility and privacy of deployment, backhaul usage and reduced network administration.
