IEC 61158-4-18:2010 specifies the protocol which provides communication opportunities to all participating data-link entities in a synchronously-starting cyclic manner, according to a pre-established schedule, and in a cyclic or acyclic asynchronous manner, as requested each cycle by each of those data-link entities. The described procedures are applicable to instances of communication between systems which support time-critical communications services within the data-link layer of the OSI or fieldbus reference models, and which require the ability to interconnect in an open systems interconnection environment. Profiles provide a simple multi-attribute means of summarizing an implementation's capabilities, and thus its applicability to various time-critical communications needs. This bilingual version (2012-08) corresponds to the monolingual English version, published in 2010-08. 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: Editorial improvements and Addition of cyclic data segmenting.