Recommendation ITU-T G.8265.1/Y.1365.1 contains the ITU-T precision time protocol (PTP) profile for frequency distribution without timing support from the network (unicast mode). It provides the necessary details to utilize IEEE 1588 in a manner consistent with the architecture described in Recommendation ITU-T G.8265/Y.1365. This edition of the Recommendation defines the PTP profile for unicast mode only. Support is provided for both IEEE-1588-2008 and IEEE-1588-2019. Amendment 1 provides the following updates: Definitions Updates to use inclusive terminology Add portDS.twoStepFlag in Table A.5 and updated the description in clause 6.3.2 Changes in Annex A