Direct Attach Cable

How Direct Attach Cables are used in a Datacenter?

In the modern and ultra-high tech Datacenters of today, more bandwidth is needed and used to support the latest demands in the Networking world especially the server-virtualization environment where multiple virtual machines are being combined on a single physical host server. To be able to accommodate the growing number of operating systems and applications and at the same time providing scalability and reliability, virtualization requires noticeable increased data transmission rates between the servers and the switches in the Datacenter. At the same time the networking devices, and the pure Internet day to day use, have dramatically increased the data that has to be transmitted throughout the Datacenter including the Storage Area Network (SAN) and Network Attached Storage (NAS) environment. According to some researches done in the past couple of years, the amount of data transmission in the world is growing astoundingly, more than 20% in only 5 years. Accordingly the leading IT managers are looking for ways to reduce the cost of implementing the newest technology and at the same time provide the stable Network of tomorrow.

With these thoughts in mind the leading manufacturers started developing the new technology that would be able to meet these requirements and this is the Direct Attach Cables or DACs. This is a high density and low power consumption technology that would allow to create an in-rack 10GB/s solutions between servers and switches. Today these Direct Attach Cables are used to transmit the huge data transmissions in Datacenters mainly between switches, servers and storage devices. Because of the way they are designed, using the same ports as the Optical transceivers use, they have become hugely popular with Datacenters.

Direct Attach Cables are cables that have an Optical Transceiver type of ending connectors. They use the same ports as the Optical transceivers and they provide Ethernet, fiber channel and Infiniband solutions. These cables are mainly divided in three separate types that are most commonly used.

  • Direct Attach Passive Copper Cables- Because these cables are passive and they lack in an active circuitry component they can provide 10GB/s speeds up to 7 meters.
  • Direct Attach Active Copper Cables- With the help of the active circuitry component these cables can reach up to 15 meters providing 10GB/s or 40GB/s solution. Other than the active circuitry component this cables are designed in the same way as the Direct Attach Passive Copper Cables.
  • Active Optical Cables- These cables incorporate active optical and electrical components which can reach up to 150 meters on Multi-mode fibers. These cables can also be used as active direct attach breakout cables satisfying the various needs of Datacenters.

These cables are most commonly used for a short reach direct connection applications. They are used in the Equipment Distribution Areas where the racks are the home of the end servers and where the cabling is terminated at patch panels. For interconnection between racks these cables are used to connect servers to switches, switches to switches or storages to switches. They use an electrical to optical conversion on the cable’s ends which provides higher speed and low latency without sacrificing compatibility with the most standard optical transceivers. With the fast growing 10GB/s Ethernet solutions these cables are mainly used in the SFP Form-factor for interconnection between switches and storages in the same rack. However in the near future the 25GB/s Direct Attach Cables will start substituting the 10GB/s Direct Attach Cables making room for more bandwidth for spine switches. These 40GB/s Direct Attach Cables are already available on the market.

GBIC-SHOP BlueLan© offers different variants of, cost-effective, Twinax Direct Attach Cables, active or passive, with various connectors capable of providing the very latest in high speed network demands, QSFP, QSFP28, SFP, SFP+, QSFP Breakout and IB4X. All cables have a 5 year warranty and a lifetime support.

What are the most used interconnections within a data center?

In data center environment there are many interconnections needed from regular large numbers of ports of access switches to the large bandwidth capacity ports of backbone routers with particular cases of ports facing the connections towards storage access networks.

All these ports needs reliable connections implementations in form of  patchcords on short distances. There are two main forms of interconnection patches: AOC - Active Optical Cables and DAC-Direct Attached Cables. The target application is interconnection of top-of-rack switches with application servers and storage devices in a rack.

AOC - patch cords are constructed using optical fibers and have attached on the ends active optical components such as transceivers. Their advantage consists in protection to electromagnetic perturbations, greater bandwidth capabilities, management functions embedded in the end active parts. All these features come with a proportional higher price than twinax cables.

DAC - Direct attach cables use the twinax copper wires to transmit signals.Twinax cable is almost similar with CATV coaxial cable but not the same having two conducting wires inside covered by protective shield. They are suitable up to 10Gbps data rates and distances up to 7 meters.

Twinax versus Cat5 or Cat6 Ethernet Cables
The advantage of twinax over short distance consist in lower delay 0.1 μs versus 1.5 to 2.5 μs for current implementations of SFP+ DAC cables vs 10GBASE-T.

The power draw of Twinax with SFP+ is around 0.1 watts, which is also much better than 4–8 watts for 10GBASE-T. Cables must not be bent below their minimum bend radius, which depends upon cable size as expressed in AWG - American Wire Gauge.The 10GSFP+Cu link utilizes a receive equalizer in the host PHY/SerDes in order to compensate for the Inter Symbol Interference (ISI) introduced by the cable.

Active vs Passive DAC Cables
There are some versions of DAC which have some active modules at the ends of them performing signal re-shaping and amplification making them suitable for longer distances. The usual distance reach is within 10 meters for data center connectivity. Also, the active components permits data rates up to 40G.

The versatility of the protocols used, besides 10G Ethernet, the support for Fibre Channel, Fibre Channel over Ethernet and Infiniband, low consumption for active parts, low prices, make them competitive alternative for AOC Cables.

Passive cables are much less costly but require the host to do the work of driving it properly.

Benefits:

Tradeoffs:

  • Lower Costs
  • Higher Reliability
  • No LOS
  • No TX Disable
  • No Interrupts
  • Limited Management Interface
  • Host must drive Cu cable

 

100G Direct Attach Cables

The 40GBASE-CR4 and 100GBASE-CR10 physical layers using 7 m twin-axial cable are being developed as part of 100 Gbit Ethernet specifications by IEEE 802.3bj workgroup.

IEEE 802.3bj define a 4-lane 100 Gbit/s backplane PHY for operation over links consistent with copper traces on with lengths up to at least 1 m and a 4-lane 100 Gbit/s PHY for operation over links consistent with copper twinaxial cables with lengths up to at least 5 m.

SC282801LXM30 - BlueLAN© 100GBASE-CR4 QSFP28 Direct Attach Cable (passive), 1 to 2 Meter, AWG 30, this item is the current offer that is able to transmit a total of 100Gps troughput.

How Direct Attach Cables (DAC) are used in a Datacenter?

In the modern and ultra-high tech Datacenters of today, more bandwidth is needed and used to support the latest demands in the Networking world especially the server-virtualization environment where multiple virtual machines are being combined on a single physical host server. To be able to accommodate the growing number of operating systems and applications and at the same time providing scalability and reliability, virtualization requires noticeable increased data transmission rates between the servers and the switches in the Datacenter. At the same time the networking devices, and the pure Internet day to day use, have dramatically increased the data that has to be transmitted throughout the Datacenter including the Storage Area Network (SAN) and Network Attached Storage (NAS) environment. According to some researches done in the past couple of years, the amount of data transmission in the world is growing astoundingly, more than 20% in only 5 years. Accordingly the leading IT managers are looking for ways to reduce the cost of implementing the newest technology and at the same time provide the stable Network of tomorrow.

With these thoughts in mind the leading manufacturers started developing the new technology that would be able to meet these requirements and this is the Direct Attach Cables or DACs. This is a high density and low power consumption technology that would allow to create an in-rack 10GB/s solutions between servers and switches. Today these Direct Attach Cables are used to transmit the huge data transmissions in Datacenters mainly between switches, servers and storage devices. Because of the way they are designed, using the same ports as the Optical transceivers use, they have become hugely popular with Datacenters.

Direct Attach Cables are cables that have an Optical Transceiver type of ending connectors. They use the same ports as the Optical transceivers and they provide Ethernet, fiber channel and Infiniband solutions. These cables are mainly divided in three separate types that are most commonly used.

  • Direct Attach Passive Copper Cables- Because these cables are passive and they lack in an active circuitry component they can provide 10GB/s speeds up to 7 meters.
  • Direct Attach Active Copper Cables- With the help of the active circuitry component these cables can reach up to 15 meters providing 10GB/s or 40GB/s solution. Other than the active circuitry component this cables are designed in the same way as the Direct Attach Passive Copper Cables.
  • Active Optical Cables- These cables incorporate active optical and electrical components which can reach up to 150 meters on Multi-mode fibers. These cables can also be used as active direct attach breakout cables satisfying the various needs of Datacenters.

These cables are most commonly used for a short reach direct connection applications. They are used in the Equipment Distribution Areas where the racks are the home of the end servers and where the cabling is terminated at patch panels. For interconnection between racks these cables are used to connect servers to switches, switches to switches or storages to switches. They use an electrical to optical conversion on the cable’s ends which provides higher speed and low latency without sacrificing compatibility with the most standard optical transceivers. With the fast growing 10GB/s Ethernet solutions these cables are mainly used in the SFP Form-factor for interconnection between switches and storages in the same rack. However in the near future the 25GB/s Direct Attach Cables will start substituting the 10GB/s Direct Attach Cables making room for more bandwidth for spine switches. These 40GB/s Direct Attach Cables are already available on the market.

CBO BlueLan© offers different variants of, cost-effective, Twinax Direct Attach Cables, active or passive, with various connectors capable of providing the very latest in high speed network demands, QSFP, QSFP28, SFP, SFP+, QSFP Breakout and IB4X. All cables have a 5 year warranty and a lifetime support.