IEC 61158-4-28 Ed. 1.0 b:2023

The data-link layer provides several types of messaging communications between devices in an automation environment.

This part of IEC 61158 provides a means of connecting devices through a partial mesh network, such that most failures of an interconnection between two devices can be circumvented. In common practice, the devices are interconnected in a non-redundant hierarchical manner reflecting application needs.