5 Protocol functions

Abstract

After introducing the basic concepts of services, protocols, and layered architectures in previous chapters we return once more to the protocol as the main concept to have a closer look at it. Communication protocols typically contain a number of procedures and mechanisms which appear in many protocols. These procedures are usually called protocol functions. Many of these protocol functions in turn use other protocol functions. Which protocol functions are applied in a protocol depends on the purpose of the protocol. Protocols in higher layers usually apply other functions than those in lower layers. There are, however, many functions that are applied in many protocols, such as connection management, flow control, error control, or synchronization. These and other protocol functions are introduced in this chapter. With this introduction, we want to give the reader a deeper insight into the most important protocol mechanisms, the diversity of their procedures, and the complexity resulting from this.