DAC,direct attach copper cable, is a kind of fixed high speed copper cable assembly. It consists of shielded twinax copper cable with pluggble connectors on either end with varying gauges from 24 to 30AWG: The longer the distance, the higher the AWG rating should be. DAC is comprised of a twinax copper cable terminated withSFP+/SFP28/QSFP+/QSFP56/QSFP28 connectors on both ends, which can provide an electrical connection directly into active equipment. DAC cables can be classified into two fold: passive DAC & active DAC. Both passive and active DAC cables can transmit electrical signals directly over copper cable. The former can deliver without signal conditioning, while the latter has electric components inside the transceivers to boost signals. Normally speaking, DAC cables are used to connect switches, servers, and storage inside racks.