Direct Attach Copper (DAC) cables use twinax copper with modules at each end for direct device communication. Unlike optical connections, DACs have fixed lengths and limited distance at higher speeds. As speeds increase to 100GbE and beyond, cables become thicker and less flexible due to increased electromagnetic shielding. DACs remain essential for rack-to-rack connectivity where cost and simplicity matter most.

Breakout DACs split high-speed connections like QSFP+ to multiple SFP+ ports, increasing port density without additional hardware. While DACs typically reach shorter distances than fiber optics, they consume less power and cost significantly less. Active DACs offer slightly more distance than passive versions but require more power, making them less common in modern data centers focused on energy efficiency.

DAC cables dominate within-rack connectivity due to their simplicity and reliability. When selecting DACs, consider speed requirements and vendor compatibility, as some manufacturers restrict third-party cables. Despite the fiber optics trend, DACs remain critical components in data center infrastructure, providing cost-effective solutions for high-speed connections where distance limitations are acceptable.