The Developing of Ethernet Technologies

Fibermart
Wednesday 07 August, 2013
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The most mature and common of the network applications is Ethernet. Over the past 25 years, despite stiff competition from more modern network architectures, Ethernet has flourished. In the past 10 years alone, Ethernet has been updated to support speeds of 100Mbps, 1Gbps (about 1000Mbps) and 10Gbps. Currently 40 and 100 Gigabit Ethernet are being standardized in the IEEE 802.3b committee. 40 and 100 Gigabit Ethernet will be deployed over optical fiber for 100 meters or greater, and research is progressing to make it available over UTP for distances up to 10 meters. The knowledge of Ethernet technologies development will be provided in this article.

10Mbps Ethernet Systems

The first Ethernet standard (Ethernet II) worked at a speed of 10 Mbps. Following passages will describe the technology used at this point in time.

10Base-5

The earliest version of Ethernet ran on a rigid coaxial cable that was called Standard Ethernet cable, but was more commonly referred to as thicknet. While thicknet was difficult to work with (because it was not very flexible and was hard to install and connect nodes to), it was reliable and had a usable cable length of 500 meters. 10Base-5 systems can still be found in older installations, typically used as backbone cable, but virtually no reason exists for you to install a new 10Base-5 system today.

10Base-T

10Base-T means 10Mbps Ethernet over unshielded twisted-pair cable. Maximum cable length (network device to network card) is 100 meters. 10Base-T Ethernet is less common today and has been overtaken by 100Base-T. Even though 10Base-T uses only two pairs of a four-pair cable, all eight pins should be connected properly in anticipation of future upgrades or other network architectures.

10Base-F

Specifications for using Ethernet over fiber-optic cable existed back in the early 1980s. Originally, fiber-optic cable was simply used to connect repeaters whose separation exceeded the distance limitations of thicknet cable. The original specification was called Fiber-Optic Inter-Repeater Link (FOIRL), which described linking two repeaters together with fiber-optic cable up to 1,000 meters (3,280´) in length. The cost of fiber-optic repeaters and fiber-optic cabling dropped greatly during the 1980s, and connecting individual computers directly to the hub via fiber-optic cable became more common. Originally, the FOIRL specification was not designed with individual computers in mind, so the IEEE developed a series of fiber-optic media specifications. These specifications are collectively known as 10Base-F. It is uncommon to use optical fiber at these slow speeds today.

10Base-2

10Base-2 is still an excellent way to connect a small number of computers together in a small physical area such as a home office, classroom, or lab. The 10Base-2 Ethernet uses thin coaxial (RG-58/U or RG-58 A/U) to connect computers together. This thin coaxial cable is also called thinnet.

100Mbps Ethernet Systems

The 100Mbps version of 802.3 Ethernet specifies a number of different methods of cabling a Fast Ethernet system, including 100Base-TX, 100Base-T4, and 100Base-FX.

100Base-TX

The 100Base-TX specification uses physical-media specifications developed by ANSI that were originally defined for FDDI (ANSI specification X3T9.5) and adapted for twisted-pair cabling. The 100Base-TX requires Category 5e or better cabling but uses only two of the four pairs. The eight-position modular jack (RJ-45) uses the same pin numbers as 10Base-T Ethernet.

100Base-T4

The 100Base-T4 specification was developed as part of the 100Base-T specification so that existing Category 3–compliant systems could also support Fast Ethernet. The designers accomplish 100Mbps throughput on Category 3 cabling by using all four pairs of wire; 100Base-T4 requires a minimum of Category 3 cable. The requirement can ease the migration path to 100Mbps technology.

100Base-FX

Like its 100Base-TX copper cousin, 100Base-FX uses a physical-media specification developed by ANSI for FDDI. The 100Base-FX specification was developed to allow 100Mbps Ethernet to be used over fiber-optic cable. Although the cabling plant is wired in a star topology, 100Base-FX is a bus architecture.

Gigabit Ethernet (1000Mbps)

1000Mbps Ethernet was supported only on fiber-optic cable. The IEEE 802.3z specification included support for three physical-media options (PHYs), each designed to support different distances and types of communications:

1000Base-SX

Targeted to intra-building backbones and horizontal cabling applications such as to workstations and other network nodes, 1000Base-SX is designed to work with multimode fiber-optic cable at the 850nm wavelength.

1000Base-LX

Designed to support backbone-type cabling such as inter-building campus backbones, 1000Base-LX is for single-mode fiber-optic cable at 1310nm, though multimode fiber can be used for short inter-building backbones and intra-building cabling applications.

1000Base-CX

Designed to support interconnection of equipment clusters, this specification uses 150 ohm STP cabling similar to IBM Type 1 cabling over distances no greater than 25 meters. When cabling for Gigabit Ethernet using fiber, you should follow the ANSI/TIA-568-C standards for 62.5/125 micron or 50/125 micron multimode fiber for horizontal cabling and 8.3/125 micron single-mode fiber for backbone cabling. See Table 6 of Annex D in ANSI/TIA-568-C.0.

1000Base-T

Gigabit Ethernet over Category 5 or better UTP cable where the installation has passed performance tests specified by ANSI/TIA/EIA-568-B. Maximum distance is 100 meters from equipment outlet to switch. The IEEE designed 1000Base-T with the intention of supporting Gigabit Ethernet to the desktop. One of the primary design goals was to support the existing base of Category 5 cabling.

10 Gigabit Ethernet (10,000Mbps)

The IEEE approved the first Gigabit Ethernet specification in June, 2002: IEEE 802.3ae. It defines a version of Ethernet with a nominal data rate of 10 Gbit/s. Over the years the following 802.3 standards relating to 10GbE have been published: 802.3ae-2002 (fiber -SR, -LR, -ER, and -LX4 physical-media-dependent devices[PMDs]), 802.3ak-2004 (-CX4 copper twin-ax InfiniBand type cable), 802.3an-2006 (10GBASE-T copper twisted pair), 802.3ap-2007 (copper backplane -KR and-KX4 PMDs), and 802.3aq-2006 (-LRM over legacy multimode fiber -LRM PMD with electronic dispersion compensation [EDC]). The 802.3ae-2002 and 802.3ak-2004 amendments were consolidated into the IEEE 802.3-2005 standard. IEEE 802.3-2005 and the other amendments have been consolidated into IEEE Standard 802.3-2008. In the premises environment, 10 Gigabit Ethernet is mostly used in data center storage servers,high-performance servers, and in some cases for intra-building backbones. It can be used for connection directly to the desktop.

10GBASE-SR

10GBASE-SR (short range) uses 850nm VCSEL lasers over multimode fibers. Low-bandwidth 62.5/125 micron (OM1) and 50/125 micron (OM2) multimode fiber support limited distances of 33–82 meters. To support 300 meters, the fiber-optics industry developed a higher bandwidth version of 50/125 micron fiber optimized for use at 850nm.

10GBASE-LR

10GBASE-LR (long range) uses 1310nm lasers to transmit over single-mode fiber up to 10 kilometers. Fabry-Pérot lasers are commonly used in 10GBASE-LR optical modules. Fabry-Pérot lasers are more expensive than 850nm VCSELs because they require the precision and tolerances to focus on very small single-mode core diameters (8.3 microns). 10GBASE-LR ports are typically used for long-distance communications.

10GBASE-LX4

10GBASE-LX4 uses coarse wavelength division multiplexing (WDM) to support 300 meters over standard, low-bandwidth 62.5/125 micron (OM1) and 50/125 micron (OM2) multimode fiber cabling. This is achieved through the use of four separate laser sources operating at 3.125Gbps in the range of 1300nm on unique wavelengths. This standard also supports 10 kilometers over single-mode fiber. 10GBASE-LX4 is used to support both standard multimode and single-mode fiber with a single optical module. When used with standard multimode fiber, an expensive mode conditioning patch cord is needed. The mode conditioning patch cord is a short length of single-mode fiber that connects to the multimode in such a way as to move the beam away from the central defect in legacy multimode fiber. Because 10GBASE-LX4 uses four lasers, it is more expensive and larger in size than 10GBASE-LR. To decrease the footprint of 10GBASE-LX4, a new module,10GBASE-LRM, was standardized in 2006.

10GBASE-LRM

10GBASE-LRM (long reach multimode) supports distances up to 220 meters on standard, lowbandwidth 62.5/125 micron (OM1) and 50/125 micron (OM2) using a 1310nm laser. Expensive mode conditioning patch cord may also be needed over standard fibers. 10GBASE-LRM does not reach quite as far as the older 10GBASE-LX4 standard. However, it is hoped that 10GBASE-LRM modules will be lower cost and lower power consumption than 10GBASE-LX4 modules. (It will still be more expensive than 10GBASE-SR.)

10GBASE-T

10GBASE-T supports 10Gbps over Category 6A UTP or Category 7 shielded (per ISO/IEC 11801Ed. 2) twisted-pair cables over distances of 100 meters. Category 5e is supported to much lower distances due to its limited bandwidth. Special care needs to be taken in installing Category 6A cables in order to minimize alien cross-talk on signal performance.

40 and 100 Gigabit Ethernet

100 Gigabit Ethernet (100GbE) and 40 Gigabit Ethernet (40GbE) are groups of computer networking technologies for transmitting Ethernet frames at rates of 100 and 40 gigabits per second, respectively. The technology was first defined by the IEEE 802.3ba-2010 standard. This will be deployed over OM3 50/125 multimode optical fiber for 100–200 meters, and research is progressing to make it available over UTP for distances up to 10 meters. This could be the speed point at which there is mass conversion of copper to fiber-based systems.

Conclusion

Ethernet has become the unifying technology enabling communications via the Internet and other networks using IP. Its popularity has resulted in a complex ecosystem between carrier networks, data centers, enterprise networks, and consumers with a symbiotic relationship between the various parts. While symbiotic in nature, the different applications in the Ethernet ecosystem are growing at different rates: server and computing applications are growing at a slower pace than network aggregation applications. This divergence in growth rates spurred the introduction of two higher rates for the next generation of Ethernet: 40 Gigabit Ethernet for server and computing applications and 100 Gigabit Ethernet for network aggregation applications. This will enable Ethernet with its proven low cost, known reliability, and simplicity, to continue to evolve and be the ubiquitous connection for traffic on the Internet.