THE OSI REFERENCE MODEL

Having a model in mind helps you understand how the pieces of the networking puzzle  together. The most commonly used model is the Open Systems Interconnection (OSI) reference model. The OSI model, first released in 1984 by the International Standards Organization (ISO), provides a useful structure for de?ning and describing the various processes underlying networking communications. The OSI model is a blueprint for vendors to follow when developing protocol implementations. The OSI model organizes communication protocols into seven levels. Each level addresses a narrow portion of the communication process. Figure 2.1 illustrates the levels of the OSI model.