IEC 61158-6-4-:2014 defines the protocol provided to define the wire-representation of the service primitives defined in IEC 61158-5-4, and define the externally visible behavior associated with their transfer. This standard specifies the protocol of the Type 4 fieldbus application layer, in conformance with the OSI Basic Reference Model (ISO/IEC 7498-1) and the OSI application layer structure (ISO/IEC 9545). This secod edition cancels and replaces the first edition published in 2007 and constitutes a technical revision. The main changes are: editorial improvements and corrections.