This part of IEC 61158 is one of a series produced to facilitate the interconnection of automation system components. It is related to other standards in the set as defined by the three-layer Fieldbus Reference Model, which is based in part on the Basic Reference Model for Open Systems Interconnection. Both Reference Models subdivide the area of standardization for interconnection into a series of layers of specification, each of manageable size. The Data Link Service is provided by the Data Link Protocol making use of the services available from the Physical Layer. This part of the IEC 61158 series defines the Data Link Service characteristics that the immediately higher-level protocol may exploit.