What is Ethernet IEEE 802.3

What is Ethernet IEEE 802.3

Ethernet, IEEE 802.3, is one of the most widely used standards for computer networking and general data communications. It is widely used in all forms of data networking from connecting to home Wi-Fi hubs to business data networks and telecommunications networking.

The Ethernet standard has been used for many years, being steadily updated to meet the requirements of growing technology. Data communication speeds have steadily risen and Ethernet, IEEE 802.3 has increased its speeds accordingly.

Although to many, Ethernet is familiar because Ethernet connections are widely used for in the home for wired connections between computers and broadband hubs, but they also provide the essential connectivity for data networking systems used in large enterprises.

Ethernet is probably most widely known because of the short Ethernet patch cables with their RJ45 connectors which are used to connect most desktop computers to data network routers. These make Ethernet connections very easy to make, thereby increasing the ease of use and popularity of Ethernet technology.

Accordingly Ethernet forms the basic technology for connectivity for most local area networks these days. Versions of it have also been devised for larger enterprises. Carrier Ethernet is one example of how the technology has been adapted for use by network operators or carriers.

Ethernet history

The Ethernet standard was first developed by the Xerox Corporation as an experimental coaxial cable based system in the 1970s. Using a Carrier Sense Multiple Access / Collision Detect (CSMA/CD) protocol to allow multiple users it was intended for use with LANs that were likely to experience sporadic use with occasional heavy use.

The success of the original Ethernet project lead to a joint development of a 10 Mbps standard in 1980. This time three companies were involved: Digital Equipment Corporation, Intel and Xerox.

The Ethernet Version 1 specification that arose from this development formed the basis for the first IEEE 802.3 standard that was approved in 1983, and finally published as an official standard in 1985.

Since the first Ethernet standards were written and approved, many updates have been introduced to keep the Ethernet standard it in line with the latest technologies that are becoming available.

Ethernet network elements

The Ethernet IEEE 802.3 LAN can be considered to consist of two main elements:

  • Interconnecting media: The media through which the signals propagate is of great importance within the Ethernet network system. It governs the majority of the properties that determine the speed at which the data may be transmitted. There are a number of options that may be used:
    • Coaxial cable: This was one of the first types of interconnecting media to be used for Ethernet. Typically the characteristic impedance was around 110 ohms and therefore the cables normally used for radio frequency applications were not applicable. This type of cabling is not widely used for Ethernet these days as it is expensive and difficult to install.
    • Twisted Pair Cables Type types of twisted pair may be used: Unshielded Twisted Pair (UTP) or a Shielded Twisted Pair (STP). Generally the shielded types are better as they limit stray pickup more and therefore data errors are reduced. A variety of different cable types are available as the standard are always moving forwards.
    • Fibre optic cable: Fibre optic cable is being used increasingly as it provides very high immunity to pickup and radiation as well as allowing very high data rates to be communicated.
  • Network nodes The network nodes are the points to and from which the communication takes place. Although in years past, terms like DTE, data terminal equipment, and DCE, data communications equipment were used, these are seldom seen these days when looking at Ethernet communications. Instead the types of equipment seen on the Ethernet data network are what are more commonly seen:
    • Computers: Today, most computers come wit the capability for Ethernet connectivity. Most desktop computers are expected to work on a local area network, and this is almost universally Ethernet based. Today the Ethernet capability will be built into the motherboard of the computer, rather than using an optional plug in board. The physical connection is normally provided using an RJ45 style Ethernet connector.

      For laptop computers there is an increasing trend for them to be much thinner. This means that some do not have the dedicated Ethernet ports with an RJ45 connector as there is not the space for them. However they can normally connect to a local area network using Ethernet via an adapter. This will give them reliable wired connectivity if wireless connections are not used.

    • Routers, switches and hubs: The other main elements on local area networks using Ethernet as the interface medium are routers, switches and hubs. These devices enable the data to be routed around the data networks so that they can be sent and reach their relevant destinations. Although similar in some aspects, routers, switches and hubs are distinct types of devices, even if the terms tend to be misused interchangeably.
    • Miscellaneous devices: On any local area network there will be the need for a variety of devices apart from computers, routers, switches, etc. Items like printers, etc will be needed. These can be linked onto the network in a similar way to any computer.
    A variety of different devices can be connected to local area networks using Ethernet technology. Many different types of device intended for use on local area networks will have Ethernet capability.

In addition to the hardware based devices, and physical interconnections that are required for any local area network using Ethernet, software drivers are also needed. Any device with a physical Ethernet connection will have the software needed. In addition to this the popular operating systems like Windows, Apple iOS and Linus, have Ethernet capability incorporated into the basic software.

This means that additional drivers do not need to be loaded in all but the most exceptional circumstances to enable devices to connect to to an Ethernet local area network.

Ethernet network topologies

There are several network topologies that can be used for Ethernet communications. The actual form used will depend upon the requirements.

  • Point to point: This is the simplest configuration as only two network units are used. In this simple structure the cable is known as the network link. Links of this nature are used to transport data from one place to another and where it is convenient to use Ethernet as the transport mechanism.
  • Coaxial bus: This type of Ethernet network is rarely used these days. The systems used a coaxial cable where the network units were located along the length of the cable. The segment lengths were limited to a maximum of 500 metres, and it was possible to place up to 1024 DTEs along its length. Although this form of network topology is not installed these days, a very very few legacy systems might just still be in use. In view of the way in which it operates, with several nodes on the same leg, the CSMA/CD anti-collision scheme is used.
  • Star network: This type of Ethernet network has been the dominant topology since the early 1990s. It consists of a central network unit, which may be what is termed a multi-port repeater or hub, or a network switch.
    All the connections to other nodes radiate out from this and are point to point links. It is this type of network topology that is used and extended. Connections tend to extend out from a central hub using a series of routers or switches to divert the data to the required end node.

Message data collision detection

In the original forms of Ethernet, a form of data collision detection known as CSMA/CD was used. In this the nodes detected if data was being sent and if it was they would back off and resend their data later.

Nowadays, using the extended star topology, the CSMA/CD data collision detection requirement is not needed. Collisions are only possible if station and switch attempt to communicate with each other at the same time, and collisions are limited to the individual link.

Furthermore, the 10BASE-T standard introduced many years ago adopted full duplex techniques and in view of the improvements it provided, this technique became the standard for future developments of the Ethernet standard.

In full duplex, switch and station can send and receive simultaneously, and therefore modern Ethernet data networks are collision free.

How does Ethernet work?

When communicating over a data network, the Ethernet system divides the data into a set of what are termed frames. These frames have a specific format and each one contains the source and destination addresses.

The frame also contains information for error checking so that any data that is corrupted can be detected. If errors are detected then typically the higher layers of the protocol stack for the system will discard the data and request a re-transmission.

Ethernet adopts the OSI model for its protocol stack and in line with this, Ethernet itself provides services up to Layer 3, the data link layer.

Ethernet has adopted the 48 bit MAC address format that has also been used by other IEEE 802 standards and int his way there is commonality across many standards making it much easier for various data networking systems to operate alongside each other.

Metro and Carrier Ethernet

There are versions of Ethernet that are used for higher grade performance associated with large metro or wider area networks. Metro Ethernet and carrier Ethernet are two terms that are often used.

These two terms are often used almost interchangeably, but have some differences.

  • Metro Ethernet: Metro Ethernet generally refers to an Ethernet installation deployed in a metropolitan area - i.e. over a relatively wide area - wider than that of a local area network. Often business use Metropolitan Ethernet to connect multiple locations of the business to a network via an Ethernet private line. This gives some significant advantages over using the public networks in terms of speed, security and cost. Carrier Ethernet is now the over-arching term that is used to describe the type of Ethernet used for Ethernet based lines of this nature.
  • Carrier Ethernet: Carrier Ethernet or Carrier grade Ethernet is typically used to provide communication point to point communication between two points or sites or to provide links for local area networks, etc. Carrier Etthernet has developed to include a number of other services and it enables long-distance data sharing among businesses and other organizations. This considerably reduces costs, whilst also maintaining performance.

Metro Ethernet and Carrier Ethernet are now well established variants used by many carriers and service providers to allow businesses to have high performance interconnections over dedicated or shared high performance Ethernet resources.

Although Ethernet data networking was originally introduced in the 1970s it has undergone a continual process of update. This has enabled the basic concept to be maintained, whilst enabling it to provide the performance levels needed as technology and connectivity requirements increase.

Ethernet technology is used for data networking for everything from home computer networking right up to enterprise data networks where carrier Ethernet is used to carry high levels of data.

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Watch the video: The brief History and the Evolution of Ethernet - IEEE (December 2020).