This Recommendation provides an overview of the functions provided by the fine grain MTN (fgMTN) layer network and identifies the Recommendations where the functions are defined. Amendment 1 to Recommendation G.8312.20 updates the overview of fgMTN recommendation series to include the fgMTN protection and equipment recommendations. Amendment 2 to Recommendation G.8312.20 updates the CBR functional requirements and the overview of fgMTN recommendation series to include the fgMTN synchronization and management recommendations.