on L2 networks with P2P delay measurement (from 1588-2008 Annex J.4) The IEC, in cooperation with the IEEE, has adopted the L2P2P version as the Power Utility Auto- mation Profile (PUP) and published it jointly as IEC/IEEE 61850-9-3 (see the following section). The SDOs have agreed to keep these two documents aligned. Note that the IEC standards refer to IEC 61588:2009 (edition 2.0) when referring to PTP, which is just the IEC's adopted version of IEEE 1588-2008. The IEC is adopting 1588-2019 as edition 3 without changes. Annex A specifies how PTP clocks are attached over redundant, simultaneously active paths using PRP or HSR with no single point of failure at the network level. It is quite a detailed annex (about 45 pages) showing how PTP is implemented in combination with these protocols (it is not a pro- file). The idea is for PTP to run on top of HSR/PRP to make use of its redundancy features. However, Annex A extends the default BMCA because of the need to support doubly connected ports synchronized by the same master. Because messages from the same grandmaster appear on two different interfaces, there needs to be an application-specific process to select the port with the best clock quality. Any PTP clock that is doubly connected needs to support this extension. Annex B defines a new profile for doubly attached clocks named "IEC/IEEE 61850-9-3 Precision Time Protocol profile for Power Utility Automation." It is simply the same L2P2P profile from An- nex C that has an additional requirement that the clocks must be doubly attached (using the methods in Annex A). The difference between 61850-9-3 (also copied from Annex C) allows the PTP clocks to be doubly attached (redundancy clause 9), but does not require it, whereas the 62439-3 Annex B profile requires it. IEC 62439-3:2016 also acts as the foundation for a range of other standards used to deal with packet-based time synchronization for the power industry. Figure 7-16 illustrates the high-level in- terrelationships between these various PTP standards. Note