Market Background Of Direct Attach Cables


With the rapid development of network technology and network application, as a data center for centralized exchange of information data and storage of network devices, it has been challenged with high bandwidth, high reliability and low latency. According to the IDC Industry Development Research Report, as of 2011, the global IDC market maintained a steady growth trend. The overall market size reached 22.26 billion U.S. dollars, an increase of 21.5%. Emerging markets such as Asia Pacific were the biggest drivers of growth for the entire industry. In the next 2-3 years, the Asia-Pacific region will enter a period of high growth in the deployment and upgrading of data centers. 

In China, many traditional data centers are built according to the standards of the 1990s. In the structure reliability, energy consumption and refrigeration system can not meet the expansion and upgrading needs, facing high energy consumption and high operating costs. Meanwhile, data center operators are just out of the economic crisis and pay more attention to cost and budget than ever before. Under the pressure of increasing traffic volume, data centers are looking for appropriate and effective ways to upgrade and expand in a more economical manner. In the face of IDC Market trends, the data center access layer from Gigabit to 10 Gigabit will be an irreversible trend.

10G SFP+ Direct Attach Cables

SFP (Small Form-factor Pluggables) is an upgraded version of Gigabit Interface Converter (GBIC), which is the half size as GBIC module and the functions same as the GBIC. This translates the gigabit electrical signals into optical signals. The 10G module has experienced from the 300Pin, XENPAK, X2, XFP development, the final realization of the same size with the SFP 10G signal transmission, that is SFP+. SFP+ meets the high-density requirements of switch and server depend on its miniaturization and low cost. It was promoted from the 2002 standard and has replaced XFP as the mainstream of the 10G market by 2010. SFP Developed by a number of manufacturers agreement MSA specification, SFP+ compliance agreement: IEEE 802.3ba, SFF-8431, SFF-8432.

The cable assemblies (including the two-terminal interface module) used for the interconnection between network cards are called Direct Attach Cables (DAC). The DAC cable assemblies are mainly used for the stack connection of Ethernet 10G switches. The TOR Switch and server interconnect, Fiber Channel device interconnect, InfiniBand device interconnect, and server/storage interconnect.

SFP+ DACs are also referred to as 10GSFP+ copper, 10GBASE-CR or SFP+, 10GBASE-CX1, or 10GbE & SFP copper cables. Direct connection, using a passive biaxial cable assembly and directly connected to the SFP+ module.SFP+ direct attached cable length is 1, 3, 5 and 7 meters, support customization. Low power, low cost and low latency advantages.

Direct Attach Cables

In the past, server manufacturers using the motherboard comes with RJ45 port is free, and now 10G port is expensive. Pluggable port module has become a cost barrier can not be ignored. At present, there are three mainstream server NICs in a 10G Ethernet data center: 10G Base-CR, SFP+ network card. This optical network card needs to be connected with 10G SFP+ Direct Attach Cable (DAC). There are also 10G Base-T copper network card and 10G Base-SR optical network card. Compared with the overall cost and power consumption, optical link cost is about 1.3 times that of copper link.10GBase-T copper NIC uses the RJ45 interface, the current market volume of the card is relatively large power consumption, many users are looking forward to 10G Base-T power can have a more substantial decrease.

DAC cable 

TOR architecture is already one of the development direction of virtualized data center, access layer switch placed above each cabinet, reducing the cabling between each cabinet and the head cabinet. The number of interconnections between servers and access switches is increased, the distance is shortened, and the delay is greatly reduced. With this architecture, DAC cables can demonstrate the advantages of low cost and low power consumption, as well as the benefits of short-range interconnects.



Server port transfer rate from 1Gbps to 10Gbps, access layer uplink to core backbone link to 40Gbps / 100Gbps is the network to achieve barrier-free full line speed. Since 2011, the major manufacturers have already launched the 40G or even 100G interface switches that are regulated by MSA. Each switch uplink at least 4-8 40G ports down to at least 24 10G ports. Many people think that before 40G is just a transitional phase of 100G. At present, under the overall environment, the cost of data center construction is tightening. Compared with copper links, the cost of 40G optical links is more than 3-4 times that of 10G links. The cost of 100G optical link is higher. The 4x25Gbps 100G transceiver originally adopting WDM technology is 250 times that of 10G transceiver. Especially, the cost of 100G single-mode optical link exceeding 10km is even more prohibitive. Although the cost is gradually declining now, the relative price is still high, at least the cost is reduced to 2-3 times of 40G, 5-6 times of 10G, can really enter 100G era. As a result, 40G will become the mainstream trend for Ethernet server ports for at least the next three years. The Ethernet Alliance did technical work on physical-layer media: single-mode fiber, OM3 and OM4 multimode fiber, backplane, copper, and the appropriate interfaces in the 40G and 100G Ethernet Technology Overview, June 2010 Analysis, and gives the corresponding requirements, such as duplex rate, transmission distance, bit error rate, maximum/minimum data frame.

 Direct Attach Cables

The QSFP+ (Quad Small Form-factor Pluggable) interface module of 40G transmission rate arises as the times require, and the QSFP+ pluggable module supports four channels of data transmission up to 40Gbps at the speed of 10Gbps per channel. QSFP+ cable used for high-density, high-speed I/O; multichannel interconnects; storage networking equipment interconnects; and switch routing equipment interconnects. QSFP+ is also regulated by the MSA, compliant protocols IEEE 802.3ba, SFF-8436, QDR InfiniBand.

The 40G QSFP+ to 4x10GSFP+ DAC translates the downstream 40G ports of TOR access layer switches into four 10G channel server ports for use in server cabinets. The 40G QSFP+ DAC is used for the backbone link from the data center access layer network to the core network. However, the maximum transmission distance of the 40G QSFP+ DAC is no more than 7 meters. For the data center backbone link, the length of DAC is more difficult to apply. Because of the cost advantage of the 40G QSFP+ DAC , it can be used in high-speed stacking of container-type data centers and equipment. For the backbone link In the current state of the art, more will be required to support parallel multimode optical fiber links over longer distances.

Development Trend

 10G SFP+ and 40G QSFP+ turn 4x10G SFP+ DAC has been large-scale deployment between the access layer network and the server. Third-party market research firm forecasts that by 2015, direct-to-copper market share of 10G and above DACs will increase from 28 million U.S. dollars in 2010 to 1.5 billion U.S. dollars. Direct Attach Cables will show significant growth in the next 2-3 years with about 30-40% market share in the future 10GbE port applications. The 40G QSFP+ DAC Direct Attach Cable, due to distance limitations, will be used in specific data centers or in equipment stacks and in the industrial arena, and data center trunks will still be dominated by optical fibers for longer periods in the future. TIA and ISO standards organizations are already developing 100-meter solutions based on 40G copper cables and we still have to wait for the standardization of 40G copper cables. For 10G networks, the DAC cable will be a 10G cabling solution that we can not ignore.

Huizhou C-FLINK Technology Co.,Ltd. has long time focused on the data center industry network interface technology development, with the progress and development of technology, the market situation will also have new changes. As a professional data connectivity solutions provider, we can provide the appropriate interconnect solutions and services.

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