ProtoRINA is a user-space prototype of the Recursive InterNetwork Architecture. RINA is a new architecture that builds on the fundamental principle that "networking is inter-process communication". As a consequence, RINA overcomes inherent weaknesses of the current Internet, e.g., security, mobility support, and manageability. ProtoRINA serves not only as a prototype that demonstrates the advantages of RINA, but also as a network experimental tool that enables users to program different policies using its built-in mechanisms. In this note, we introduce ProtoRINA as a vehicle for making RINA concepts concrete and for encouraging researchers to use and benefit from the prototype.