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WHAT IS A DIRECT ATTACH COPPER CABLE (DAC)?

A Direct Attach Copper cable or DAC cable is a twinax copper cable used to connect ports to switches, routers, servers or data storage equipment for short transmission distance. 

It consists of a shielded twinax copper cable with pluggable connectors on either end such as SFP+, SFP28, QSFP28 and QSFP+.

Direct Attach Cables are used in short reach, high density, high speed interconnect data centre applications. They are designed for networking, data storage and telecom systems where you need the highest possible network efficiency, low power consumption and low latency at an affordable price. 

There are 2 types; Passive and Active. Active DAC has a signal amplification, class clock, data recovery(CDR) and equalizer technology to support longer distances than standard passive DAC cables which have no electrical components built into the cable assembly.

We recommend a Passive DAC is used for transmission of up to 7m and an Active DAC is suitable for 7-15m.

Common Application of Direct Attach Cables

DAC cables are most often used to connect equipment located within the same data rack with short transmission distance requirements, typically 1-2m. That said we do offer 0.5-10m lengths.

10G Ethernet Connections

An SFP+ to SFP+ DAC cable is plugged directly into both pieces of equipment to establish a 10G Ethernet connection with no need for additional Fibre Patch Leads.

40G Ethernet Connections

A QSFP+ to QSFP+ DAC cable is plugged directly into both pieces of equipment to establish a 40G Ethernet connection with no need for additional Fibre Patch Leads. 

They are also used to connect one 40G port to up to four 10G Ethernet ports. In this application, a 40G DAC breakout cable is needed with 1 x QSFP+ (40G) one end and 4 x SFP+ (4x10G) on the other end. Of course this solution is constrained by distance between the hardware ports, but it can be a very straightforward, cost effective solution in the right environment

100G Ethernet Connections

A QSFP28 to QSFP28 DAC cable is plugged directly into both pieces of equipment to establish a 100G Ethernet connection with no need for additional Fibre Patch Leads. 

They are also used to connect one 100G port to up to four 25G Ethernet ports. In this application, a 100G DAC breakout cable is needed with 1 x QSFP28 (100G) one end and 4 x SFP28 (4x25G) on the other end. Of course this solution is constrained by distance between the hardware ports, but it can be a very straightforward, cost effective solution in the right environment

For more information please contact us and we will be happy to help