This International Standard is applicable to high-availability automation networks based on the ISO/IEC 8802-3 (Ethernet) technology. This International Standard specifies - a classification scheme for network characteristics (see 268H Annex A); - a methodology for estimating network availability (see 269H Annex B); - a set of communication protocols that realize high availability automation networks via the use of redundancy and that can be used in a variety of applications (see Clauses 270H 5, 271H 6, 272H 7, 273H 8).