Design of Distributed System Protocols Based on Standard FDL'sPerfecto Mari?o, Miguel Angel Dom?nguez, Francisco Poza, Juan B. NogueiraIn this work the protocol WorldFIP for industrial communication networks, is specified with the formal specification language LOTOS. The paper introduces the main features of WorldFIP particularly those related to its data link layer. The methodology used and the description of specification are explained with the data types implemented. Following that, instances of tests developed for verifying the specification are described..This allows us to detect a lack of efficiency in the protocol with the transfer of messages. Results and new guidelines of this work are explained in the last paragraph devoted to conclusions and future works. The LOTOS specification of the WorldFIP protocol shows that formal description techniques provide powerful CAE tools for advanced designs in the field of industrial communications.