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Maximizing 10GBase-T connectivity in data centers (Part 1)

Posted: 11 Apr 2012 ?? ?Print Version ?Bookmark and Share

Keywords:10GBase-T? RJ45 connectors? PHYs?

Ethernet at 10G speeds is now here. The growing importance of cloud computing and the increasing utilization of unified data/storage connectivity and server virtualization by enterprise data centers, have conspired to elevate the importance and popularity of 10Gbps Ethernet. Not long ago considered an exotic connectivity option relegated to high-capacity backhaul, more and more applications are taking advantage of the availability and cost-effectiveness of 10GE links. As was the case with three prior generations of Ethernet, the ubiquity, the ready and familiar management tools, and the compelling cost structure are allowing 10G Ethernet (10GE) to quickly dominate the computer networking scene.

Crehan Research, an industry analyst of data center technologies, claims over 8 million 10GE ports in data center switches for 2011. And in its January, 2011, report, The Linley Group, another industry analyst, predicted robust 10GE growth and estimated that 10GE NIC/LAN-on-motherboard (LOM) shipments alone will surpass 16 million ports in 2014.

Starting in 2002, The Institute of Electrical and Electronics Engineers (IEEE) has created several standards for 10G Ethernet connectivity. The more popular ones include:

???10GBase-SR uses optical modules with 850nm lasers to work over multimode fiber.
???10GBase-LR uses optical modules with 1310nm lasers to work over single-mode fiber.
???10GBase-LRM uses optical modules with 1310nm lasers and works over multimode fiber.
???10GBase-ER uses optical modules with 1550nm lasers and works over single mode fiber with reach up to 40km.
???10GBase-KX4 which operates over four copper backplane lanes with distance up to 1m
???10GBase-KR which operates over a single backplane lane with distance up to 1m
???10GBase-T, which operates over Category 6 (Cat6) and Category 6A (Cat6A) twisted pair copper cabling with distance up to 100m.

In addition, a non-IEEE Standard approach called SFP+ Direct Attach has also gained popularity. This method uses a passive twin-ax cable assembly, which connects directly into a SFP+ module housing. The cable assemblies are ordered in pre-specified lengths and come with the SFP+ module form factor connecters attached. Distances between three and 10m are supported, depending on the coaxial cable thickness used.

The focus of this two-part article is on the 10GBase-T connectivity option. Of all the options available, 10GBase-T, which is also known as IEEE 802.3an, is arguably the most flexible, economical, backwards-compatible, and user-friendly 10GE connectivity option available. It was designed to operate with the familiar unshielded twisted pair cabling technology, which is already pervasive in environments using and can interoperate directly with 1GE. It is capable of covering, with a single cable type, any distance up to 100m and, therefore, reaches 99 percent of the distance requirements in data centers and enterprise environments. In this article, we will explore the basics of 10GBase-T technology, explain the many benefits it brings to the data center, outline the current state of the art, and explore upcoming advances and their implications.

10GBase-T basics
Ratified in June 2006, IEEE 802.3an provided a stable blueprint for chip manufacturers to develop and introduce compliant and interoperable devices allowing for 10Gbps communications over unshielded twisted pair cabling. 10GBase-T is the fourth generation of so-called BASE-T technologies, which all use RJ45 connectors and unshielded twisted pair cabling to provide 10Mbps, 100Mbps, 1Gbps, and 10Gbps data transmission while being backwards-compatible with prior generations. Because BASE-T devices have used an auto-negotiation protocol defined by the IEEE to determine the capabilities supported by the other end of the link, this backward compatibility has meant that upgrades could be performed one end at a time, allowing quick and easy incremental improvement of network speed without either changing the wiring or forklift upgrades of equipment.

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