Recommendation ITU-T G.8312 describes a transport technology for metro networks (MTNs), including transport of distributed radio access network (D-RAN) and centralized radio access network (C-RAN) traffic. This technology leverages existing and emerging pluggable Ethernet modules and reuses flex Ethernet (FlexE) implementation logic. Amendment one adds several clarifications and also provides test vectors. Amendment two adds an annex to describe the fine grain MTN path and the associate elements. Amendment three adds a new annex A subclause and appendix V to describe the method of mapping CBR clients into fgMTNP and a new annex B to describe the fine grain MTN path hitless resizing mechanism. Amendment four adds a new appendix VI to describe CBR client bit mapping including AMP and GMP, it also update Table A.1 to define PT value for fgCPU.