Self-FEXT (far-end crosstalk) cancellation, also called vectoring, is mandatory in G.fast.

The Equal-Level Far-End Crosstalk (ELFEXT)

The scope of Recommendation ITU-T G.993.5 is specifically limited to the self-FEXT (far-end crosstalk) cancellation in the downstream and upstream directions.

Category 1 and 2 cables can either meet the required parameter specifications for interpair skew, far-end crosstalk, attenuation, and differential impedance, or they can meet the required nonequalized/equalized eye diagram requirements.