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10GBASE-T vs SFP+ vs DAC: Which to Choose for 10GbE Data Center Cabling?
Generally, 10GbE network can be achieved by 10GBASE-T copper module, SFP+ fiber optical transceiver and SFP+ direct attach cables. 10GBASE-T vs SFP+ vs DAC: which to choose for 10GbE data center cabling? Reading this article to get a further understanding of these three products.
10GBASE-T Module, SFP+ Module & SFP+ DAC Introduction
The 10GBASE-T SFP+ copper transceiver is specifically designed for high speed communication links that require 10 Gigabit Ethernet over Cat 6a/7 cable. It is the first 10G copper SFP RJ45 module that offers 10Gb/s communication over Ethernet copper cables, which is compliant with SFF-8431 and SFF-8432 MSA standards. Learn more about the 10GBASE-T SFP+ copper module at Understanding of 10GBASE-T SFP+ Copper Transceiver Modules.
10GbE SFP+ fiber optical transceiver is also used for 10G network transmission with a maximum transmission distance of 100km. It has various types, like 10GBASE-SR, 10GBASE-LR, 10GBASE-ER, 10GBASE-ZR and so on. Know more information about the different 10GbE SFP+ module types on Module Guide: 10G SFP+ Types Classification.
As for SFP+ DAC, it uses a copper 10GbE cable that comes as active or passive twinax cable assembly and connects directly into an SFP+ housing with a very short link distance. So the SFP+ direct attach cables are often used for interconnecting a stack of ToR switches and short-distance connections between switch ports and Ethernet interfaces on servers and storage devices in a rack. Read 10G SFP+ Direct Attach Copper Media System-10GSFP+Cu for more information on 10G SFP+ DAC cables.
10GBASE-T vs SFP+ Fiber vs SFP+ DAC: What Are Their Differences?
In this part, the 10GBASE-T module, SFP+ fiber transceiver and SFP+ DAC differences are elaborated in the following descriptions from the points of flexibility, backward compatibility, latency, distance, and cost.
Flexibility & Backward Compatibility
10GBASE-T copper module adopts the interoperable, standards-based 10GBASE-T technology, which uses the legacy RJ45 connection and can auto-negotiate between 10/100/1000Mbps and 10 Gigabit speeds. In other words, 10GBASE-T copper cabling is backward compatible effectively with standard copper network devices. The 10GbE SFP+ modules allow 10G Ethernet and 10G fiber channel applications that cannot be compatible with copper-based cabling systems, and sometimes they can be used on 1G fiber optic networking. As for SFP+ DAC, it is not backward-compatible with existing Gigabit Ethernet switches and only used for 10GbE switches.
Latency
Low latency is paramount to ensure fast response time and reduce CPU idle cycles, which increases data center efficiency and ROI. 10GBASE-T copper modules adopt PHY standard to use block encoding to transport data across the copper cables without error. The PHY standard specifies 2.6 microseconds for the transmit-receive pair, and the size of the block requires that latency to be less that 2 microseconds. SFP+ uses simplified electronics without encoding, and its typical latency is around 300 nanoseconds per link. We can see from the following figure that, SFP+ fiber provides lower latency than the other two products.
| Number of Links | 10GBASE-T SFP+ | SFP+ Fiber | SFP+ DAC |
|---|---|---|---|
| 1 | 2.6 | 0.1 | 0.3 |
| 2 | 5.2 | 0.2 | 0.6 |
| 3 | 7.8 | 0.3 | 0.9 |
| 4 | 10.4 | 0.4 | 1.2 |
| 5 | 13.0 | 0.5 | 1.5 |
| 6 | 15.6 | 0.6 | 1.8 |
Figure 1: 10GBASE-T vs SFP+ Fiber vs SFP+ DAC Latency
Distance
10GBASE-T RJ45 modules can reach up to 100m using Cat6a or Cat7 cables in 10G Ethernet network cabling system. And the 10GbE SFP+ optical transceiver can reach a very long transmission distance of maximum 100km through single mode fiber optic cables. But the SFP+ DAC can only provide a maximum distance of 10 meters (about 33 feet) based on active copper cables, which are much more commonly used in intra-rack and inter-rack connections. If the distance is not a problem, the SFP+ DACs tends to be an optimal option because of lower power consumption and lower latency.
Cost
The 10GBASE-T RJ45 module usually uses Cat6a/7 cable for cabling which are often less expensive than 10GbE SFP+ fiber optic cables. In the data center, with hundreds of required cables, this can turn into big savings. In addition, the 10GBASE-T copper network can maximize the utilization of existing copper structured cabling. This will also save much capital expenditure. 10GbE SFP+ transceivers are much more expensive than 10GBASE-T copper modules by using single mode or multimode fiber optic cables and the maintenance budgets for fiber-cabling systems will be expensive in the future. As for the SFP+ DAC cables, they are the cheapest of these three kinds of products. The only shortcoming is the transmission distance is very limited.
The following table shows the basic parameters of 10GBASE-T SFP+ module, 10GbE SFP+ module and SFP+ DAC.
| Types | 10GBASE-T SFP+ | 10G Fiber SFP+ | SFP+ DAC |
|---|---|---|---|
| Data Rate | 10/100/1000Mpbs; 10Gbps | 1Gbps; 10Gbps | 10Gbps |
| Interface | RJ-45 | LC Duplex; LC Simplex | / |
| Cable Type | Cat6a/Cat7 Cable | MMF/SMF | Twinax Cable |
| Transmission Distance | 100m | 220m/300m/2km/10km/40km/80km/100km | ≤10m |
| Power Consumption | 2-5w | 0.7w | 0.7w |
| DOM Support | No | Yes | Yes |
| Cost | Less Expensive | Most Expensive | Cheapest |
10GBASE-T, SFP+ Module & SFP+ DAC Applications
Though 10GBASE-T copper modules, 10GbE SFP+ transceivers and SFP+ DAC cable can be used for achieving the 10G Ethernet transmission, they can be applied for different application scenarios in the data center and enterprise networks. 10GBASE-T SFP+ copper transceivers are often applied for Top of Rack, Middle of Row, End of Row architectures or intermediate, horizontal and main distributions areas in data center and enterprise networks within 100m. And the 10GbE SFP+ optical transceivers are commonly applied for ToR, MoR, EoR, backbone core networks in data centers with a maximum link distance of 100km. As for the SFP+ direct attach cables, they are usually used for the Top of Rack intra-cabinet connectivity from servers to ToR switches within 10m, such as interconnected with top-of-rack switches and servers, as well as between storage devices in one rack or neighboring racks. The following figures are the typical applications for 10GBASE-T copper modules, SFP+ transceivers and SFP+ DAC cables.
Figure 2: 10GBASE-T SFP+ Copper Module Application With Server/Storage Appliances
Figure 3: 10GbE SFP+ Optical Transceivers Direct Connection
Figure 4: SFP+ DAC Direct Connection
Conclusion
In summary, 10GBASE-T copper modules, SFP+ transceivers and SFP+ DAC cables are different in flexibility, backward compatibility, distance, application latency and cost. You can choose them according to your network requirements. To be noted, with the popularization of fiber optic cabling systems, the copper cables will be gradually dropped out of the market. Therefore, the 10GBASE-T will be gradually stepped out of the industry. And with the decreasing prices and low power consumption, 10GbE SFP+ transceivers will be an ideal solution in the data center network.