Ethernet is a MAC protocol. It is one way to regulate physical access to network transmission media.



Ethernet is actually a collection of networking standards, some of which are outdated and not used any more. Today there are three versions of Ethernet that you are likely to encounter in a small network, distinguished by their transmission speeds".

  • Standard Ethernet (also known as 10BASE-T): Transfers data at a maximum of 10 megabits per second (abbreviated 10 Mbps). At today's prices, it is possible to set up a simple eight device standard Ethernet LAN for less than $100. This assumes that all of the nodes require expansion boards. If all the nodes have built-in network adapters, then you can get by for about $25. However, today standard Ethernet is largely gone because almost all computers are supplied with faster versions of the standard. Although we will discuss standard Ethernet in this book as a basis for Ethernet operation, it is highly unlikely that you would install it: The next faster version costs no more and,because it is more widely used, occasionally less.
  • Fast Ethernet: transfers data at a maximum of 100 Mbps. At the time this book was written, it was the most common type of Ethernet in use for connecting client workstations.
  • Gigabit Ethernet: transfers data at a maximum of 1 gigabit per second (abbreviated 1 Gbps). At the time this book was written,Gigabit Ethernet hardware was becoming common on client workstations, although its most typical use is to connect servers to the network. If your desktop computers come equipped with Gigabit Ethernet, it is certainly reasonable to use it throughout your network, as prices for network interconnection hardware have dropped to the point where they are affordable for even small networks.
  • 10 Gigabit Ethernet: Transfers data at a maximum of 10 gigabits per second (10 Gbps). Initially designed to run over fiber optic cabling for use in WANs, 10 Gb Ethernet has now migrated to copper wire and can be used within a LAN. Keep in mind,however, that very few individual devices can transmit and receive data at 10 Gbps. Therefore, LAN 10Gb Ethernet is be stsuited for large networks where many devices share the network medium. It is highly unlikely that you would run 10 Gb Ethernet to a single desktop device; such a setup would not be economically efficient.
The next Ethernet speed jump will probably be to 40 Gbps, although there is no official standard for this speed yet. This WAN implementation is intended only for fiber optic cabling. Will there be an even faster version? Never say "never": Some writers are currently talking about 100 Gbps Ethernet, even though as of summer 2007, there wasn't even a committee working on a 40 Gb standard.

When considering Ethernet speeds, keep in mind that the transfer rates associated with each type of Ethernet are maximums. In practice, it is rare to achieve the highest transfer rate. Many factors limit network speed, including the nature of the transmission media, the amount of traffic on the network, and the speeds of the hardware manipulating the network. In addition, an Ethernet that supports between 30 and 60 percent utilization is considered saturated. You will therefore never realize total use of your network media. (However, the introduction of hardware known as switches as a replacement for hubs has significantly increased the utilization.)

Given that Ethernet and the data transmission protocols that run on top of it (TCP/IP, IPX/SPX, and AppleTalk) are independent, when you choose Ethernet over some other form of physical network, you are restricting your hardware choices rather than your software choices. As you will see,the type of Ethernet you choose dictates to some extent what hardware you use. However, your software choices are not limited.

The Speed and Bandwidth Connection

The types of Ethernet are defined in terms of their maximum transmission speeds. Nonetheless, they can in most cases use the same type of wiring.Assume, for example, that standard, Fast, and Gigabit Ethernet are all using the same wire medium. Electrical signals can travel at only one physical speed over the medium. How can this be true if there are multiple Ethernet speeds?

The answer lies in how we actually look at speed. The measures of Ethernet speed are actually what is known as throughput, the number of bits that arrive at a destination per unit time. There are two ways to affect throughput.The first is to speed up the rate at which the bits travel, but this is dictated by the physical properties of the wire. Since we cannot speed up the travel rate of a single bit, the only other choice is to increase the number of bits traveling together. For example, if you can send four bits per unit time,your throughput will be greater than if you can send only one. This is directly analogous to widening a road from two to four lanes but leaving the maximum speed limit the same. Widening the road does not allow an individual car to travel faster, but does allow more cars to cover the same distance in the same period of time.

The number of bits that can travel together at the same time represents the bandwidth of the transmission medium. If we can increase the bandwidth,we can increase the throughput without changing the maximum physical transfer speed of bits down the wire. Fiber optic cabling, for example, is very fast not only because each bit can travel at the speed of light, but because so many tiny glass fibers can be bound together into a single cable to provide a high bandwidth.

Ethernet Standards

The types of Ethernet about which you have just read are defined in a set of standards prepared by the Institute of Electrical and Electronic Engineers(IEEE). The committee in charge of the standards for LANs is known as IEEE LAN 802, and the group within it that handles media access control standards as 802.3. Each 802.3 standard describes a method for media access control and the transmission media that should be supported.

Although the name of the IEEE may not suggest thatthe organization has anything to do with computing, keep in mind that the IEEE predates computers. It has evolved to encompass a wide range of computing standards and applications.

Although in most cases you won't be concerned directly with the specifications themselves and the rather strange numbering scheme that goes along with them, you may find that equipment and cable vendors use the standard numbers to identify the type of Ethernet for which a product is appropriate.You should therefore at least be familiar with the type of Ethernet each standard represents. This book identifies the standards that accompany each type of Ethernet cabling as we explore hardware details in the following chapters.

Ethernet History

Originally, Ethernet was the brainchild of one person: Robert Metcalfe. Int he early 1970s, while working at Xerox PARC on the "office of the future" project, Metcalfe was intrigued by a radio network in Hawaii known as AlohaNet. One problem faced by AlohaNet's media access control was that its maximum efficiency was 17 percent: That is, a maximum of 17 percent of the transmission units sent actually reached their destination.According to Metcalfe, the unreceived portions of the transmissions were"lost in the ether."

Metcalfe developed an alternative media access control method that allowed up to 90 percent of the transmission units to reach their destination. Originally known as "experimental Ethernet," it transferred up to 3 Mbps. He refers to the cabling along with data travel as "the ether," hence the name Ethernet.

The first Ethernet specifications were published in 1980 by a consortium of commercial hardware vendors ~ Digital Equipment Corporation (now a part of Compaq Corp.), Intel, and Xerox (DIX). By that time, the transmission speed had been increased to 10 Mbps.

The IEEE adopted Ethernet as a LAN standard and published its initial specifications as 10BASE5 in 1983. Later, Ethernet was also endorsed as a standard by the ISO. Ethernet is therefore an international standard for one way in which nodes on a LAN can gain access to transmission media.

Throughout its history, Ethernet has moved to faster and faster standards:
  • 1986: The standard for 10BASE2 was approved, still running at 10 Mpbs.
  • 1991: The standard for 10BASE-T was approved. Although still running at 10 Mpbs, it used copper wiring, making it much easier to handle than earlier standards.
  • 1995: The standard for 100 Mpbs Ethernet was approved. This is the slowest speed in general use today.
  • 1998: The standard for 1000 Mbps (Gigabit) Ethernet using fiber optic cable was approved.
  • 1999: The standard for 1000 Mbps Ethernet using copper wire was approved.
  • 2002: The standard for 10,000 Mbps (10 Gigabit) Ethernet was approved. This type of Ethernet is for wide area rather than local area networks.

As of early 2007, standards committees were beginning to explore the possibilities for 40 Gigabit and 100 Gigabit Ethernet, although speeds beyond 1 Gigabit currently aren't designed for use in local area networks.

Ethernet Communications

With the advent of the internet the world is no more divided by invisible boundaries. People from any part of the world can stay connected with the rest of the world with ease. Gone are the times when the snail mails or posts took ages to reach another country or continent. Communications media have grown in leaps and bounds and it takes hardly a second for an email to reach some remote part of the world. From normal postal system and telephones today we have other highly advanced communication systems like internet, wireless communication; mobile communication etc. Internet networks can be broadly classified as local area networks and wide area networks. LANs or local area networks use Ethernet framework for the computer networking.

Using Ethernet hundreds of computers can be connected to one source and the data and work can be shared or transferred with ease thereby saving time. All computers in one area stay connected and thus it is also called local area network. Internet technology has grown thus enabling the best form of communication. The faster mode of communication through the internet depends upon the network used by the operating system. The speed at which the computer connects to the internet is very important as a slow connection might delay the work flow or data transfer. Ethernet works as a base station wherein all the data reaches before being transferred to other computers on the network. It is used effectively these days for commercial purposes to help clients keep connected with their customers and other branch office staffs with ease. It enables fast tracking of the sales of many branch offices or the transaction taking place in all the different branches of the same company. Thus a CEO sitting in Auckland will get immediate and live update of what is happening in Pakistan or Canada.

Many newer versions of Ethernet have been updated regularly as the need for more performance based services becomes imperative. The needs of organisations differ and so does the size of the network. The cost for setting up an Ethernet network depends upon the number of computers that is to be connected on the network. The computers thus connected through the Ethernet network will share a common operating system, security features and unique identification certificates. It uses special routers, switch or modems for this according to the need or necessity. It needs minimal hardware and that is mostly Ethernet cables to connect. It can be used for both wired and wireless interfaces. Even for personal use one can set up the Ethernet connection to connect 2-3 computers within the same home network. Thus it is extremely useful to create a common communication network within an area. Knowing what ethernet communications are can be very useful to all technocrats and even the laymen as everyone is using computers at home and in the office.