IEC 61158-4-12:2010(E) specifies procedures for the transfer of data and control information from one data-link user entity to one or more user entity; the structure of the DLPDUs used for the transfer of data and control information by the protocol of this standard, and their representation as physical interface data units. The procedures are defined in terms of the interactions between DL entities (DLEs) through the exchange of DLPDUs; the interactions between a DL service (DLS) provider and a DLS-user in the same system through the exchange of DLS primitives; the interactions between a DLS-provider and the MAC services of ISO/IEC 8802-3. 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: bug fixes and editorial improvements.