mance monitoring options," for details. On-path performance metrics: There is also an additional (optional) mechanism to report syn- chronization accuracy metrics from various points along the PTP timing path. Each node on the path implementing this feature (including TCs) updates the accuracy metrics based on its contri- bution to the expected degradation in time accuracy. A set of metrics can be included in the ENHANCED_ACCURACY_METRICS TLV to determine an overall expectation of time inac- curacy. This TLV is propagated down the timing path for nodes to use as required. For example, a PTP profile could define an aBMCA that makes use of this data to allow the slave to select the most accurate grandmaster. See section 16.12, "Enhanced synchronization accuracy metrics (optional)," for details. It is evident that v2.1 contains numerous new, interesting, and helpful options. In the interests of backward compatibility, many of them are optional, but it is clear there will be increased adoption of some of these options over the next several years. 7.7.1 Next Steps for IEEE 1588 The publishing of the 2019 edition is not the end of the evolution of the standard. The IEEE has already begun projects to address topics that will be included in future amendments of IEEE 1588. These projects are described in what the IEEE calls project authorization requests (PAR) and are known by the titles P1588a through P1588g. These projects are expected to complete through the end of 2022. These projects will address the following topics over the next few years: Security: Define a default security profile and proceed on aspects of security (for example, key management) BMCA enhancements: Enhancing the data made available to support the BMCA; provides in- formation to allow the adoption and specification of alternative BMCAs; corrections and clarifications Management: Define YANG and MIB data models Transport: Specification for mapping PTP to OTN Calibration: Enhances support for latency and asymmetry calibration Additional edits and clar