Part III: Host
Chapter 9, Logical Link Control and Adaptation Protocol, describes the multiplexing layer.
Chapter 10, Attributes, explains how a stateless protocol can be used to obtain the state of a device efficiently.
Chapter 11, Security, is the main body of protocol that is used to provide security services.
Chapter 12, The Generic Access Profile, ties all the pieces of the puzzle together into a high level abstraction that application writers can use.