Introduction
Category 5 UTP, token ring, twisted pair, hub, switch, gigabit……….What do all these items have in common?  In case you didn’t figure it out right away, all the above listed items are related to Ethernet in some way or another.  During the mid to late 1990’s as prices of commodity PC Hardware began to decline, households began to acquire more than one PC, and networking them together became increasingly popular.  It wasn’t long thereafter that the Internet really gained steam, resulting in explosive growth of companies that produced networking and home networking products.  Most people that own a home network don’t give Ethernet or network cabling too much thought these days.  It’s just a cable that plugs into the network interface card on one end and into a modem/switch on the other, and then things work.  While it is true that DIY (Do-It-Yourself) home networking has simplified immensely over the years, there is still a lot that must go on behind the scenes for a network to work properly.  So, how does Ethernet really work on the technical level and how has it evolved since its invention almost 30 years ago?  Is there really Ether involved?  What’s the difference between a hub and a switch and how these work together with Ethernet?  The purpose of this article serves to answer some of these questions by providing a historical background of Ethernet, an in-depth discussion of how the protocol works, advancements in Ethernet technology, and finally a short discussion of common Ethernet network building blocks, namely hubs and switches. 

It should be noted that this is not meant to be a definitive guide to Ethernet.  It is mainly my intent to provide a more in depth look of how Ethernet works and how the technology has evolved since its inception.  Naturally, given the extensiveness of the subject, I can’t cover every little thing in detail, but I will hit on many of the main points and ideas in the discussion that follows.  Should you need/want more information after reading this article, I ask that you please consult the sources I’m listing at the end of the article.

With that bit of a disclaimer out of the way, let’s get started looking at the history of Ethernet.

Part I:  Beginnings of Ethernet
The original Ethernet topology was invented in the 1970’s by Bob Metcalfe and David Boggs and was called 10base5 or “thick” Ethernet (thick because it used thick coaxial cabling).  What does the notation 10base5 mean?  Well, the 10 represents the maximum bandwidth (in this case 10Mbit/s), base just means that baseband signaling is used, and 5 tells the maximum permissible distance (in this case it is 500m).  A 10base5 Ethernet setup essentially works as follows:  A “tap” or connection is made to the core of the “Ether” (which is really coaxial cable).  This tap actually contained in the transceiver that is fastened around the cable.  A transceiver is really nothing more than a device that can both receive and transmit electrical signals.  Certainly, a device such as this would be critical to have two-way network communication. 

A 10base5 Transceiver

Moving along further now, a cable runs from the transceiver to an appropriate interface, which is part of the PC’s controller expansion card.  The transceiver/controller cable itself can have up to five twisted copper pairs.  Two of these pairs are used for data transfer, two more for control signals, and the last pair may or may not be used to power the transceiver.  Besides being able to send and receive signals, the transceiver is also capable of detecting collisions; however, I will examine this concept more later in this article.  Suffice it to say at this point that this primitive setup by Metcalfe and Boggs was the first successful Ethernet network.  As the matter of fact, their original 10base5 setup ran at a blazing 2.94Mbps with 256 hosts connected over a 1 mile interval.  Quite impressive given the time period.

After 10base5 technology had emerged, a couple other Ethernet technologies were invented as well, and deserve to be mentioned here.  One of these, 10base2 or “thin” Ethernet (due to the fact that is used thin coaxial cable as opposed to 10base5’s thick cabling), has a few key differences.  Most notably is the fact that now simple Bayonet Neill-Concelman (BNC) connections were used to connect to the ether (coaxial cable) as opposed to tapping into the cabling as was done by a transceiver.  The transceiver portion itself was now part of the PC’s controller expansion card.  As you might have picked up on already, the range of 10base2 Ethernet is significantly shorter than 10base5, coming at just under 200m (185m actually to be exact).

While 10base5 and 10base2 Ethernet are similar in that they both allow nodes connected to them to share a common transmission medium, the emergence of 10baseT Ethernet (T meaning twisted pair) brought with it a new device called a hub where data cables would come together  (the details of hubs will be discussed later in this article).  The advantage of such a setup was that if a cable broke, only the machine with the broken cable would be affected instead of having the whole network go down with a shared medium topology like 10base5 or 10base2.  It should also be noted that 10baseT used twisted pair copper cabling from the PC’s controller card to a device called a hub (to be discussed in detail later on), eliminating the need for bulky coaxial cable and BNC connectors.  The figure below shows a common 10baseT hub:

A 10baseT Hub