IEC 61158-6-3:2010 defines in an abstract way the externally visible behaviour provided by the Type 3 fieldbus application layer. It specifies the protocol provided to: define the wire-representation of the service primitives specified in IEC 61158-5-3, and define the externally visible behaviour associated with their transfer. It specifies the protocol of the Type 3 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 second edition cancels and replaces the first edition published in 2007 and constitutes a technical revision. The main changes with respect to the previous edition are: - corrections, in Table 10 and Table 48; - clarification in 6.9.1.2; - expired patents deleted and new patents disclosed. This bilingual version published in 2012-07 corresponds to the English version published in 2010-08.