Recommendation ITU-T G.8021/Y.1341 specifies both the functional components and the methodology that should be used in order to specify the Ethernet transport network functionality of network elements; it does not specify individual Ethernet transport network equipment. This Recommendation, together with Recommendation ITU-T G.8012/Y.1308, supersedes Recommendation ITU-T G.8021.1/Y.1341.1 (10/2012). This Recommendation also removes items formerly considered for further study and incorporates terms formerly defined in Recommendation ITU-T G.8001/Y.1354 (04/2016). Amendment 1 updates clause 11.1, specifying support for the ODUflexP to ETH adaptation function using idle mapping procedure (IMP) by reference to Recommendation ITU-T G.798 (2023), and incorporates Implementer's guide 1 for Recommendation ITU-T G.8021/Y.1341 (2022). Amendment 2 provides additional referencing of Recommendation ITU-T G.8013/Y.1731 (06/2023) to facilitate interpretation, improves the description of tagged ETH_AI traffic units under Figure 9-3, and addresses editorial issues.