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10 Gigabit Ethernet Overview

The ink was hardly dry on the 10Gbase-T (10 gigabit Ethernet over UTP) standard and the industry discussion swung to the next big thing – 40 Gigabit and 100 Gigabit Ethernet. While the latest technology being developed always makes for interesting discussion, it is the deployable technology that exists today that receives the most day-to-day conversation. To that end, we are only just beginning to see 10 gigabit Ethernet actually being deployed in local area network (LAN) environments.

The IEEE standards organization recently ratified the IEEE802.3an-2006 reference standard defining 10GBase-T allowing for 10 gigabits per second data transmission over Category-6a unshielded twisted pair (UTP) cabling at up to 100 meters distance. Since this standard is relatively new and coupled with the fact that the fiber standards and interfaces continue to be refined, I thought it may be beneficial to review some of the different copper and fiber standards and interfaces associated with the different 10GBase standards.

In the table below, you will find the 10GBase standard listed along with the media type and maximum distances supported:

As you can see from the table, the 10GBase-T standard is not supported on Cat 5 or Cat 5e cabling. In fact, it requires Cat 6 or better cabling to be in place to minimize the effects of crosstalk and to provide adequate distances to reach most links within a data center. I found an interesting article discussing the challenges the IEEE overcame in writing the 10GBase-T standard. Even though the 10GBase-T standard was ratified in late 2006, the general market availability of the silicon and associated switches is not expected to arrive until mid-2008. In addition, since most end users are looking at a cabling upgrade when moving to 10G, many are seriously evaluating the potential of fiber optic cabling rather than replacing their Cat 5e with Cat 6a.

As you can see from the table above, the 10GBase-X fiber standards have been around for a few years. These interfaces have been undergoing tremendous change and while they have been pluggable devices from the outset of 10G, they have seen reductions in both size and cost over the last few years.

Most 10Gb fiber deployments in use today utilize the XENPAK modules, however, the most recent deployments have begun using the XFP, a much smaller optical interface approximately 1.5x the size of the current 1000Base-X SFPs generally available on the market today. SFP+ holds the most promise for the future as it will be the same size as a current 1000Base-X SFP, however, the cages that hold the SFPs will not be backward compatible to 1000Base-X. In addition, since some of the electronics contained within the XFP and XENPAK modules is being removed to reduce the form factor, this functionality must be incorporated into the 10Gbase silicon chips. That requires additional lead time for actual switch and/or media converter designs based on SFP+ to reach the market. The advent of the SFP+ is expected to reduce the cost of the optics to a slight premium over the current 1000Base-X pricing on the market today and holds promise for the beginning of mass-deployment of the 10Gbase-X technology. It is good to note that the SFP+ technology is being worked on by a number of transceiver manufacturers, however, it is not an approved industry standard and there is not a complete consensus on the design, even among the vendors with current 10G fiber solutions.

The actual deployment of this latest and fastest Ethernet standard has been slow at best to date, with aggregated switch fiber uplinks being the most common installation. We will see the growth of 10G ports continue to expand exponentially in the coming years with most applications in the data center or vertical risers, however, don’t expect to see 10 gigabit to the desktop any time soon. Once SFP+ becomes an industry standard and the lower per-port pricing that will come along with it, we will start to see the true market acceptance of 10 gigabit Ethernet.

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