|  |  | Overview
After data packets provided by the four lower layers travel through the transport layer, they are turned into sessions by the layer 5 protocol or OSI session layer. This is done by implementing various control mechanisms. In this chapter, you will learn about these mechanisms including accounting, conversation control, that is, determining who can talk when, and session parameter negotiation. This chapter also describes how the session layer coordinates service requests and responses that occur when applications communicate between different hosts. You will learn about the processes that occur as data travels through the session layer, such as dialogue control and dialogue separation that enable applications to communicate between the source and destination.