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10GBASE-T Cabling vs 10G SFP+ DAC, which one is better?

10GBASE-T vs SFP+ DAC

01
Mar

Some recent advances in information and data center technology are helping to drive demand for 10GbE architectures, including virtualization and server clustering, network convergence, and advanced storage architectures. The Internet is also a major factor, the new forms of Internet-based information delivery and the explosive growth of digital and social media content. For a variety of reasons, 10GbE has become a flexible unified data center architecture.

For 10Gb Ethernet (10GE) switches and NICs, SFP+ transceivers and DAC cables connected to them have been widely used. Compared with 10GBase-T, SFP+ DAC has certain advantages: lower delay, lower power consumption, lower cost, and the technology is now available and stable. 10GBase-T offers a range of different benefits – familiarity, longer reach, and use of structured cabling and patch panels. So, in the end, choose 10G SFP+ DAC or 10GBASE-T for network cabling? This article will discuss this topic.

There are three options for 10GbE interconnect for specific intended uses:

  1.  SFP+ DAC Cable: These connections are ideal for deployment of blade chassis or 10GbE in racks over short distances.
  2.  Fiber cabling: Fiber optic connections are ideal for high traffic aggregate areas such as network backbones.
  3. 10GBase-T: 10GBase-T cabling is the third choice for top-of-rack switches or end-of-row usage models.

About 10GBASE-T

In the early days of Ethernet, there were several PHY standards, including various forms of coaxial cable, but Ethernet was widely adopted only after running on twisted-pair cables and as a point-to-point rather than an unstructured loop. It is practical to connect an Ethernet cable to each desktop next to the telephone line and set all connections in a wire cabinet. The connector for a twisted pair is an RJ45 connector. When Ethernet speed increases to 100 Mbps and then increases to gigabit speed, the same method is still maintained. Although cable requirements continue to evolve to maintain 100-meter distance standards, the basic method of using twisted-pair and RJ45 connectors remains the de facto standard.

10GBase-T requires a newer Cat 7 or Cat 6A up to 100 meters but can work on shorter distance Cat 6, Cat 5E or Cat 5 cables. 10GBASE-T cabling is backward compatible with 1G ports and these ports will still be used for IPMI and other low bandwidth devices. You can get a 10GBASE-T switch and connect everything you have. Used with 10G SFP+ DAC, it is difficult to find two ports that are adequate for all 10G and 1G devices.

Comparing cost

The SFP+ DAC is a lower cost alternative to fiber, but it can only reach 10 meters. It requires the purchase of an adapter card and requires a new top of rack (ToR) switch topology. DAC Cables are much more expensive than structured copper channels and cannot be field terminated. This makes the DAC more expensive than 10GBASE-T. Many networks now have Cat 6 or Cat 6a cabling installed, so they are ready for 10GBase-T. Any existing fiber can be reused for 10GbE. The new Cat 6 or Cat 6a cable can be added at a lower cost than direct-attached dual-axis copper or fiber multi-mode connections. Finally, training and knowledge transfer costs can be reduced because IT personnel are already familiar with Ethernet technology and RJ-45 connectors. Because SFP+ DAC does not have the flexibility and longer distance of 10GBASE-T, it only applies to 10GbE short-distance cabling.

Comparing Latency

The 10GBase-T PHY standard uses block coding to enable data to pass through the cable without error. The block encoding requires reading the data block into the transmitter PHY, running a mathematical function on the data, and sending the encoded data over the link. The opposite happens at the receiving end. The standard specifies 2.6 microseconds for the transmit-receive pair, and the size of the data block indicates that the wait time cannot be improved by approximately 2.0 microseconds per link. The SFP+ DAC cable uses simpler electronics without the need for code blocks. Typical latency is about 300 nanoseconds per link.

By comparison, we find that SFP+ DAC provides lower latency, but 10GBASE-T and SFP+ fiber cabling provides higher latency

Comparing Distance

Use the latest Cat 6A or Cat 7 cable, 10GBase-T up to 100 meters. The standard has been designed to allow patch panels and jumper cables. The SFP+ DAC provides a maximum distance of 10 meters (about 33 feet) based on passive copper cable. There are no patch panels used with DACs.

Comparing Flexibility

SFP+ DAC is not backward-compatible with existing GbE switches and only used for 10GbE switch.

Where rose, 10GBASE-T SFP+ is backward compatible with existing 1 GbE networks. Therefore, 10GBASE-T cabling offers the most flexibility and the lowest cost media.

Conclusion

From the comparison, we know that both 10GBASE-T cabling and 10G SFP+ DAC have their own advantages. SFP+ copper cable cabling is more suitable for use in data centers application, 10GBASE-T cabling will be better for wiring closets because of its flexibility and cost.

Original Article Source https://www.optcore.net/10gbase-t-cabling-vs-10g-sfp-dac/