Miscellaneous

10 Gigabit Ethernet, 10GE IEEE 802.3ae

10 Gigabit Ethernet, 10GE IEEE 802.3ae

10 Gigabit Ethernet is an Ethernet standard that can carry data at a rate of 10 gigabits per second.

10 Gigabit Ethernet can be a little long to write and so it is often shortened to 10GbE, 10GE or 10G Ethernet - any of these abbreviations refers to the same standard.

Although initial use was in core networks and then in large data networks, the standard is now gaining acceptance local area networks and even in some more commonplace areas where cost may have been prohibitive before.

Need for 10 gigabit Ethernet

When the 10 gigabit Ethernet standard was published in 2002 it took some years before it started to gain traction on the wider community as a result of cost. Some of the components required to build 10 Gb Ethernet interfaces were very costly and this limited its use. Accordingly the min use for many years was in the core networks for large scale providers where performance issues meant costs could be justified.

Now with the costs of the components and hence the interfaces for 10 Gb Ethernet falling, its use has entered many other areas of data networking, down to even small local area networks.

As the name of the standard implies, it provides a ten fold increase in data speed over that of 1 gigabit Ethernet. It can transfer 1 gigabit per second and this equates to 1 250 MB per second.

Many ordinary computers would struggle to cope, and 1 GE is more than fast enough. However, some local area networks using video applications may benefit from it where sharing of very large data files might be needed. Also with technology moving forwards and faster Internet and other connections being needed, 10GE will eventually become the standard.

For now there are several areas where 10 Gb Ethernet is a real benefit, specialist video applications aside.

With more services like cloud services being used and more computers are using more data intensive applications, and this means that far higher levels of data are being transferred. As a result 10 GE may be a necessity even now. Take the example of a business network where there are 10 computers on communicating with the same server. All these computers need to share the bandwidth, effectively giving each computer a throughput of 100Mbit/s using 1 GE. As the number of computers increases, so the bandwidth available falls and Gigabit Ethernet cannot really meet the speed requirements, and 10Gbit Ethernet starts to look far more viable, or even essential.

Also 10 gigabit Ethernet is used for data network backbones. Using the older 1 GE, it is quite likely that data bottlenecks will occur in the local area network. Installing 10 GE will make a significant improvement.

In addition to this, 10 Gb Ethernet is also used for long distance fibre links where it provides very significant speed improvements over what was previously available. It is in areas like these that 10 Gb Ethernet has been in use for many years.

10 Gigabit Ethernet basics

10 gigabit Ethernet is used in a number of areas. In view of its extreme speed, it is used in the more demanding areas that require fast data delivery.

10 gigabit Ethernet only supports full duplex mode. The CSMA/CD anti-collision technique used to gain access to the physical medium, and supported in previous versions is not supported in 802.3ae. In reality CSMA/CD was used less as many links were point to point and not the multiple stations on a coax line and therefore CSMA/CD was used less anyway.

The main specification for 10 gigabit Ethernet is IEEE 802.11ae. This was released in 2002 and covers the fibre based technologies. The specification applies to a variety of different fibre types, different descriptors being used according to the fibre type, mode, etc.

Then in 2004 a version of 10GE was released for twin-axial cables. This was released in 2004 under IEEE 802.3ak. This version of 10GE was developed to use four twin-axial cables, but using copper as opposed to fibre the distances that could be supported for these high data rates and the resulting signal frequencies meant the distance was limited and the applications aimed at linking switches and storage devices in data-centres, etc.

One important facet of using 10GE is that the data frame format remains the same as for the other versions of Ethernet. This enables seamless integration of 10 gigabit Ethernet into existing networks.

As full duplex operation is the only form of duplex that is used, the link distance does not affect the MAC frame size. The minimum MAC frame size will be made equal to 64 octets as specified in the previous Ethernet standards.

10 gigabit Ethernet fibre details

When 10 gigabit Ethernet was first launched, it was only available as a fibre based standard. Although a another version of 10GE is available for twin-axial cables, fibre is still the main focus.

The basic concept for an optical fibre is that laser generated light is passed along the fibre and detected at the remote end. As the light beam is modulated, this modulation is used to carry the data.

When using fibre, there are two forms of cable that are used:

  • Multimode fibre, MMF: Multimode fibre cable typically has a diameter of 50 or 62.5µm. When travelling along this form of optical fibre, the light follows a multitude of different paths giving rise to the name multimode fibre. The multiple paths give rise to what is termed differential mode delay and as a result the distances that can be covered are often limited to a maximum of around 300m. The advantage of MMF is that low cost lasers and terminations can be used, enabling this form of fibre to be used in areas where cost is more critical. Accordingly MMF is only used for 10GE where short runs are required.
  • Single mode fibre, SMF: When single mode fibre is used, the light from the laser travels along the fibre using a single path. To achieve the single path, this form of optical fibre is much narrower, typically 8.3µm and this requires that more precise components are needed for the lasers, detectors, terminations and connections. This means that the use of SMF is more costly, but very much longer distances can be achieved. SMF is used for 10 gigabit Ethernet links of distances sometimes up to 40 km.

As an example, the 802.3 standard makes reference to FDDI-grade MMF fibre. This has a core with a diameter of 62.5 µm and it possesses a minimum bandwidth of around 160 MHz·km with an 850 nm laser source.

To distinguish SMF from MMF cables, SMF cables are usually yellow, while MMF cables are orange or aqua.

10 Gigabit Ethernet versions and details

There are several versions of 10 GE that are defined according to the medium over which the data will be sent.

Although the standard for Ethernet versions normally uses the speed in Mbps as the starting number, for 10 gigabit Ethernet, this number is replaced by 10G as the number of zeros gets rather long. In other words 10GBASE-nnn is used rather than 10000BASE-nnn.

The various versions are detailed in the table below.

10 gigabit Ethernet Versions and Details
10GE VersionDetails

10GE over copper wire iEEE 802.11ak
10GBASE-CX410G Ethernet over twinax cables as defined in IEEE 802.3ak. Maximum distance is normally 15 metres. The standard Cat 6 STP or UTP cables are able to carry this.

10GE over Fibre IEEE 802.3ae
10GBASE-ERThis uses single mode fibre with a laser wavelength of 1550 nm to cover distances up to 40 km. The ER in the designator stands for Extended Reach.
10GBASE-LRThis version of 10GE uses a single mode fibre with a laser wavelength of 1310 nm to provide communications up to 10 km. The LR in the version number represents Long Reach.
10GBASE-LRM (850nm)This is a version of 10GE that uses multimode fibre and a laser light wavelength of 1850nm. When used with this light wavelength a distance of 260 metres can be achieved.
10GBASE-LRM (1310nm)10GBASE-LRM, or Long Reach Multimode is a version of 10GE that uses multimode fibre and a laser light wavelength of 1310nm. When used with this light wavelength a distance of 260 metres can be achieved.
10GBASE-LX4This uses single mode fibre with a laser wavelength of 1310 nm to cover distances up to 10 km.
10GBASE-SRThis uses multimode 850 nm fibre and provides a maximum distance of 65 metres.
10GBASE-ZRThis is a non-standard variant of 10GE that uses a single mode fibre with a laser light wavelength of 1550 nm and it is able to provide data communications over distances up to 80 km.

10GE over SONET Network IEEE 802.3ae
10GBASE-EWThis version of 10GE uses 1550 nm single mode optical fibre and provides distances of up to 40 km.
10GBASE-LWThis version of 10GE uses 1310 nm single mode optical fibre and provides distances of up to 10 km.
10GBASE-SWThis uses 850nm multimode fibre and provides distances of up to 65 metres.

Upgrading to 10 gigabit Ethernet

As the data speeds required to run businesses is increasing, so more companies will turn to 10 gigabit Ethernet for their local area networks and equipment.

When upgrading there are several items that will need upgrading:

  • 10G core switches
  • Access switches with 10G uplinks
  • 10G network interface cards for servers and storage devices.

Prices for these components are falling all the time and although they are still considerably more expensive than standard 1 GE components, they are now becoming viable for most businesses. For example the cost of an item like a 10 gigabit ethernet switch is now manageable.

Typical costs for items using 10GE is about $100 per Ethernet port. This makes an upgrade feasible for many business. They will see an improvement in speed which can relate to improved performance and profits.

10 gigabit Ethernet gives a significant increase in data transfer speed over the previous Ethernet standards, providing a ten fold increase over any other forms. Although the initial take-up was slow in some sectors, with costs falling, many more are upgrading their systems to both fibre and twinax versions of 10GE. Products like 10 gigabit ethernet switches are widely available, as are the interfaces for servers, and computers, etc.

All of this will enable businesses, even even some homes to upgrade their systems and see a noticeable improvement in speed.

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Watch the video: Understanding How Optical Fiber Type Affects Speed and Distance (December 2021).