A vast variety of design principles and formal description techniques (FDTs) have been advocated to help contend with the ever-increasing complexity of communication system development. However, the relationship between these principles and FDTs is unclear. The author formalizes a number of concepts relevant to the design principles and FDTs used to develop communication protocols. The concepts are divided into behavioral and structural concepts. Four behavioral models and a number of associated properties are defined as a basis for comparing and integrating FDTs. Two structural models, which extend the behavioral models, are then presented, and several structural concepts are defined in terms of these models. The models and properties defined within this framework are used to briefly characterize a number of FDTs. The representative FDTs considered here are Petri nets, LOTOS, a relational notation, the Z notation, and Object-Z.>