Direct attach cables, or DAC cables, are shielded high speed cables that feature SFP connectors on both ends. DAC cables are used to connect switches to servers, routers, or both. There are several different types of DAC cables, the most popular of which is the passive assembly cables, which are connected directly to the transmitting and receiving signal. Other options include active cables and active optical cables. Shielding is an important feature DAC cables, as they provide protection from electromagnetic fields.