ding on which device originates the PTP and in which direction it flows. There is also increased interest in high-accuracy timing to sup- port use cases that require timing to be delivered as a service at the microsecond level. This will in- volve a switch to using the G.8275.1 (PTPoE) profile with SyncE, mirroring the type of solution now being deployed for the mobile use cases (see Chapter 11). For more information on timing for remote PHY, please see the reference to the CableLabs specific- ations at the end of the chapter, which are part of the DOCSIS 3.1 release. There are three refer- ences, R-PHY covering RPHY, R-DTI for timing the RPHY, and SYNC that covers the require- ments on cable equipment for providing synchronization and timing as a service over the DOCSIS network (with particular focus on mobile back-haul). 9.9.1 Power Industry and Substation Automation "Chapter 2. Usage of Synchronization and Timing", describes the uses of packet-based transport to carry phase/time and frequency for other industries, with a focus on the power industry. The power industry has had a long history of using accurate time to run its widely distributed infrastructure and monitor the distribution grid of alternating current across most of the globe. These power networks typically utilize an architecture based on distributed sources of time. The primary sources in the substations are GNSS enabled and may contain many legacy timing signals, such as Inter-Range Instrumentation Group (IRIG) interfaces. Some requirements are unique to the power industry, and for this reason there are profiles of PTP specific to that industry. Chapter 7 in- cludes information on the various types of profiles supporting the power industry, including the Power Profile. The power industry seeks to improve its ability to manage its electrical distribution networks under all circumstances, including during widespread outages of GNSS systems (specifically GPS). The concern with vulnerability to GNSS outages is not unique to the power industry, nor i