Recommendation ITU-T G.8321 specifies both the components and methodology that should be used in order to specify the metro transport network (MTN) functionality of network elements; it does not specify individual MTN equipment. Amendment 1 to Recommendation ITU-T G.8321 (2022) adds Annex A that specifies new atomic functions to align with Amendment 2 to Recommendation ITU-T G.8312, including a new path layer fgMTNP which is above MTNP and corrects typos in Figure 9-8 and Figure 9-15.