on technologies to address real-time and deterministic service be- havior over Ethernet bridged networks. TSN is continuously evolving to meet an increasing interest in time-sensitive networking from an expanding number of unrelated industries. 4.3.1 IEEE and IEC The International Electrotechnical Commission (IEC) is a global organization, founded in 1906, that develops international standards and operates conformity assessment systems in the fields of elec- trical, electronics, and related technologies. In the early 19th century, the IEC had a very important function in unifying the electrical systems of the globe and even contributed to the present system of measurement by introducing units concerned with electricity and magnetism (including the Ohm, Volt, and Ampere). The IEEE and IEC have an agreement in place to increase their cooperation in developing interna- tional standards. The IEC/IEEE dual logo agreement encourages the joint development of standards by optimizing the resources and pooling the expertise to shorten the time to develop standards and publish them. Related to time synchronization, the following three specifications are quite prominent: IEC 62439- 3, IEC/IEEE 61850, and IEC/IEEE 60802. IEC 62439-3: Part of the IEC 62439 series "Industrial Communication Networks-High avail- ability automation networks," specifies the Parallel Redundancy Protocol (PRP) and High- availability Seamless Redundancy (HSR) protocol that provide seamless recovery in case of single failure of either a bridge in the network or a link between bridges. To further improve resilience in the network, the (redundancy) principles behind PRP and HSR are also extended to network clocks. Annex C of the IEC 62439-3 (2016) standard specifies two profiles of a precision clock for industrial automation: one using the layer 3, end-to-end (L3E2E) delay measurement and the other using the layer 2, peer-to-peer (L2P2P) delay meas- urement. See Chapter 7 for more information. IEC/IEEE 61850: A substation automation standard that defines