How it is useful in achieving 40G connectivity

Cabling infrastructure needs to be selected with utmost caution and care given the fact that it is the most important component of a modern day data center network expected to be ubiquitous in nature. The correct cabling solutions can help reduce the cost, maintain flexibility and achieve migration in the most seamless manner. Here is all you must know about direct attach cable and its applicability in migrating to 40G connectivity.

What is DAC CABLE?

Direct Attach Cable, or twin axial cable, is a high speed interconnect solution that links two transceivers or routers or servers directly. These connectivity products can be attached on the either side of direct attach cable without introducing any patch panel in between. The twinax cable forms direct connection allowing the IT manager to simplify the network. The main areas of application of DAC cable are data center, storage area networks and super-fast computing connectivity applications that are compliant with industry set standards.

Types of DAC cable

Active Direct Attach Cable and Passive DACs are two prevalent types of twinax cables that have their typical areas of application. While passive DACs are to be used as such and cannot be expanded or upgraded beyond the prescribed limit, the active direct attach cable because of the electronics within offers a more dynamic connectivity solution.

There is another premise for classification prevalent in DAC cable. According to this premise, the DAC can be categorized according to the type of transceivers it connects. QSFP+ transceiver is the interconnect available designed to support 40G connectivity. So, following are some of the twinax cable solutions that have been instrumental in making migration to 40G seamless as well as easier:

  1. QSFP+ cable: A QSFP+ cable is one of the most cost-effective connectivity solutions that deliver 40G connectivity within limited reach. A number of connections such as inter-rack or intra-rack, or server to server require a robust connectivity option that provides considerable degree of flexibility too. The QSFP+ cable fits the bill perfectly in such situations. The QSFP+ cables are terminated in pre-determined manner and thus, one has to be doubly sure of the required length before placing the order.
  2. QSFP+ to SFP+ cable: QSFP+ to SFP+ cables can link a single 40G QSFP+ port of a QSFP+ switch and four SFP+ ports of SFP+ on either ends, making it possible for the IT manager to connect multiple SFP+ ports with QSFP+ equipment using an easily manageable single connectivity unit. The connection looks something like this:

This assembly is tested for impedance match to ensure interoperability across SFP+ ports while ensuring minimum insertion loss. The QSFP+ to SFP+ hybrid interconnects are factory terminated to twin axial cable in order to support faster data transmission.

Advantages of using direct attach cable

There is an urgent need to look for connectivity solutions that help data centers migrate to higher speeds without disrupting the system. The direct attach cable offers plug-and-play solutions because of their hot-swappable and hot-pluggable nature, allowing the users to carry out migration process in the least possible time.

The direct attach cable is designed to complement an enriched array of protocols such as  InfiniBand 4X SDR, as well as Ethernet 10G, 40G (IEEE-802.3ba) and SONET electrical failover 40G links, Infiniband DDR, QDR etc. These cables deliver connectivity up to a distance of 5m and thus, offer idea connectivity solution for inter-rack and intra-rack connections.

Direct attach cables are usable across the same ports as optical transceivers and have no real component of costly nature as such. These are just transmitting the data from one source to another. The absence of any optical component tagged with heftier price tag makes these cables quite a cost-effective and space-efficient expansion solution for the present day data center networks.

Here is how you can connect SFP+ direct attach cable to SFP+ switch ports

  1. Hold the SFP+ connector by its sides and plug it into the SFP+ port of network switch.
  2. Slide the connector onto the port interface, and once connected properly, a sound of click will help you assure yourself of the flawless connection.
  3. After the connection, you can verify the connection using the guidelines given in interface verification module of the switch.

Why Active optical cable are preferred over twinax cable/twin axial cable

AOC (Active Optical Cable), a variant of DAC is useful in integrating multimode optical fiber, modules, control chips, fiber optic transceivers, etc into the data center network. The active optical cable provides a light-weight alternative to the DACs. These are long lasting and consistent performers that deliver higher output due to low EMI immunity and insertion loss. The low power AOCs are considered the best solutions for making the data centers future-ready because of their appreciable flexibility and less heat generation, the two causes which needed immediate solution while adopting 40G networks.


Direct attach cables and active optical cables have a distinct application area of their own. While both of these are considered useful for short-range data networks, it is the cost-effectiveness of Twinax Cisco compatible cables that make these solutions essential for 40G migrations and other related expansions. If you have made up your mind to leverage the best advantages of hot-pluggable solutions for easy migration, think of Cozlink direct attach cable that is fully tested for compatibility with intended equipment and is completely compliant with all industry set quality standards.

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