The protocol engineering plays an important role in computer networks. Designing a protocol is a challenging activity because of the complexity of the rules defining the interaction between the communicating entities. At this point, formal approaches have been proposed: Analysis and Synthesis. The synthesis approach has the advantage of avoiding errors a priori and ensuring some desirable properties during the protocol design process. In this paper, we propose a relational protocol synthesis method. The method outcome is specifications of all protocol entities serving the different service access points, which are represented in R-net diagrams