10GBASE-T vs SFP + vs DAC: how to choose?

Overview of 10GBASE-T copper module, SFP + optical module and high-speed cable:

What is 10GBASE-T copper cable SFP + transceiver？

10GBASE-T SFP + copper module is specially designed for high-speed communication link of 10Gb Ethernet, which can be transmitted over cat 6A / 7 network cable. It is the first 10g module to provide 10Gb / s speed over Ethernet copper cable and meets sff-8431 and sff-8432 MSA standards.

What is 10GbE SFP + optical module？

The 10GbE SFP + optical module can also be used for 10G network transmission with a maximum transmission distance of 100km. It has many models, such as 10gbase-sr, 10gbase-lr, 10gbase-er, 10gbase-zr, etc.

Compared with the early XFP optical module, the appearance size of the SFP + is reduced by about 30%, which is the same as that of the ordinary 1-4g optical module. SFP + only retains the basic electro-optic and photoelectric conversion functions, and reduces the SerDes, CDR, EDC, MAC and other signal control functions in the original XFP design, thus simplifying the design of 10G Optical module and reducing the power consumption. With the advantages of high density, low power consumption and lower system construction cost, the products are widely used in the 10 Gigabit Ethernet optical fiber data communication field, and are the mainstream products of the 10 Gigabit module.

Advantages of SFP + optical module

1. The size of the SFP + is more compact than that of the X2 and package (the same as the size of the SFP);

2. It can be directly connected with XFP, X2 and xenpak of the same type;

3. The cost is lower than XFP, X2, xenpak products.

4. Cost effective twisted pair copper cabling, lowest cost 10GbE Ethernet deployment

5. With the previous generation of Base-T network automatic negotiation backward compatibility, seamless migration to 10GbE

6. Field twisted pair wiring with familiar RJ-45 connectors

7. Training based on previous generations' basic knowledge and existing professional knowledge

8. Cable lengths of up to 100 meters are sufficient to support almost all data center topologies

9. Extend support for aggregate environments

What is SFP + DAC high-speed cable？

DAC means direct cable. The 10g SFP + DAC high-speed cable is a copper interconnection based on the use of cheap dual core copper cable assembly on the basis of SFP + MSA (multi-source protocol), with both ends of the copper interconnection with the connectors of the SFP + DAC. It has the advantages of low power consumption, low cost and low delay. It is the best choice for the application of short distance high speed 10 Gigabit Ethernet in modern data center. As a result, high-speed SFP + cables are often used for stacked connections to tor switches and short-distance connections between switch ports on servers and storage devices in racks and Ethernet interfaces. The high-speed cable of 10G SFP + DAC adopts silicon chip to improve the performance of the cable. Without chips, cables are considered "passive" cables. DAC high-speed cables shorter than 7 meters are passive, while cables longer than 7 meters are active. High speed cable components can meet and exceed the performance and reliability requirements of Gigabit Ethernet and fibre channel industry standards. It is a high-performance, cost-effective I / O solution for 10Gb Ethernet and 10g fibre channel applications.

What is the difference between 10GBASE-T copper module, SFP + optical module and high-speed cable of SFP + DAC?

Flexibility & backward compatibility

The 10GBASE-T copper module uses interoperable 10GBASE-T technology, which can use RJ45 connector and can automatically negotiate between 10 / 100 / 1000 Mbps and 10g speed. In other words, 10GBASE-T copper modules are backward compatible with standard copper network devices. 10GbE SFP + optical module can be used in 10G Ethernet and 10g fibre channel, but it is not compatible with copper cabling system, but sometimes it can be used in 1g fiber network. As for the SFP + DAC high-speed cable, it is not compatible with the existing Gigabit Ethernet switch, only for the connection of 10G Ethernet switch.

Delay

With the increase of Private Cloud Application utilization, the demand for low latency in large data centers is growing rapidly. Low latency is essential to ensure fast response time and reduce CPU idle cycles, which can improve data center efficiency and ROI. 10GBASE-T copper module adopts PHY standard, and can transmit data on copper cable without error by using block code. The standard defines that the transceiver time of 10GBASE-T copper module is 2.6 microseconds. The SFP + fiber is not encoded by simplified electronic equipment. The delay time of each link is about 300 nanoseconds. As can be seen from the table below, the delay of the SFP + fiber is lower than that of the other two products.

Transmission distance 

The maximum transmission distance of 10GBASE-T copper module on cat6a or cat7 network cable is 100m, and the maximum transmission distance of 10GbE SFP + optical module on single-mode optical fiber is 100km. However, the SFP + DAC high-speed cable can only transmit 10 meters at most, which is more suitable for the wiring connection within and between racks. If the transmission distance is not a factor that must be considered, the high-speed cable of SFP + DAC has lower power consumption and lower delay, so it is an ideal cabling solution for data center.

Cost

10GBASE-T RJ45 modules usually use cat6a or cat7 network cables for wiring, which is cheaper than using optical fiber cabling for 10GbE SFP + optical modules. In the data center, hundreds of cables are usually needed, and the cheap network cable can save a lot of cost. In addition, 10GBASE-T copper module can maximize the use of existing copper cable structure wiring, and also save a lot of expenses. 10g SFP + optical modules need to use relatively expensive single-mode or multi-mode fiber jumper for transmission, and the maintenance cost of optical fiber cabling system is high. SFP + DAC high-speed cable is the lowest price of the three products, the only disadvantage is that the transmission distance is very limited.

The table below shows the basic parameters of 10GBASE-T SFP + copper module, 10GbE SFP + optical module and high-speed cable of SFP + DAC.

In summary, 10GBASE-T copper modules, SFP + optical modules, and SFP + DAC high-speed cables differ in flexibility, backward compatibility, distance, application latency, and cost. You can choose the right products according to your network requirements. It is worth noting that with the popularization of optical fiber cabling system, copper cabling system will gradually withdraw from the market, so 10GBASE-T copper module will gradually withdraw from the market. With the decrease of price and power consumption, 10GbE SFP + optical module will become an ideal solution for data center network.

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