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Introduction While being, fundamentally, a well established technology, Ethernet continues to develop and evolve. First came 10Mbit/s Thick Ethernet (although actually there was an earlier version), this was followed by Thin Ethernet and Ethernet over (Unshielded Twisted Pair) UTP and fibre. Other developments have taken the technology to 100Mbit/s and 1Gbit/s and more recently 10Gbit/s. This course provides a comprehensive
look at Ethernet technologies from the ground up to where things
are today. Course AgendaThe following is an outline of the sections included in the course:
Course LengthThe course has been designed to be either one or two days with all sections being covered in both versions. Of course, however, the two day version delves into the subjects in somewhat more depth than in the one day version.
1 Introduction to, Overview of and History of Ethernet In this section we look at what LANs are all about, looking at some of the general uses that they are put to. We also look at the background and history of Ethernet. Did you know that it is derived from a ground-based radio system? However, before we get into that, we take a quick and practical look at the ISO seven-layer model.
2 Ethernet frames, MAC addresses, collisions and CSMA/CD There are two basic frame formats commonly used on Ethernet LANs. These include the original format defined in the DIX Ethernet V2 specification and the other defined in IEEE 802.3. A variant on the IEEE 802.3 format is also a format called SNAP or Sub-Network Access Protocol. This section looks at these various frame types with a look at how they may be differentiated between and why and what systems/protocols use each type. We also look at the concepts of collisions in Ethernet and a mechanism that is used to prevent issues of collisions i.e. CSMA/CD – Carrier Sense Multiple Access with Collision Detection.
3 The older Ethernet – 10BASE-5 (Thick Ethernet) and 10BASE-2 (Thin Ethernet) The original form of 10Mbit/s Ethernet ran on a coaxial cable type of 50 ohm impedance. This was named Thick Ethernet. 10BASE2 - Thin Ethernet was developed to offer a cheaper and simpler method of implementing an Ethernet LAN. As with Thick Ethernet, Thin Ethernet operates on coaxial cable. In order to extend a 10BASE-5 and/or a 10BASE-2 Ethernet LAN, a device called a repeater is used. We also cover some of the aspects of operation of an Ethernet repeater.
4 Ethernet on UTP – Unshielded Twisted Pair Most Ethernet networks today operate over Unshielded Twisted Pair (UTP) cable as opposed to the older coaxial cable based Ethernet. This section gives an introduction to UTP as a precursor to looking at its use in various types of Ethernet (i.e. 10Mbit/s, 100Mbit/s etc). We look at some of the key attributes that UTP must have in order to support such high-speed data as Ethernet generates along with the various standards for UTP cable. We cover the operation of a UTP hub, also sometimes called a multi-port repeater. Finally we see how it is possible, in some circumstances, to disable CSMA/CD thus increasing the potential throughput of Ethernet.
5 Ethernet on fibre (fiber) optic cable Copper cable is used extensively in very many networking applications. However, with the increased speed capabilities of Ethernet today, the need for the use of fibre optic cable rather than copper is ever increasing. Standards exist for all speeds of Ethernet operating over fibre, all the way from 10Mbit/s Ethernet to 10Gbit/s Ethernet. In fact, 10Gbit/s Ethernet is defined only to operate on fibre and not copper. This section looks at some of the reasons for using fibre and looks at the standard ways of using it with Ethernet.
In this section, we look at the specifics of 10Mbit/s Ethernet. This includes a look at 10Base-T and 10Base-FL, but also shows the way that 10Mbit/s Ethernet may operate across and between 10BASE-5, 10BASE-2, 10Base-T and 10Base-FL.
7 Fast Ethernet – 100Mbit/s Ethernet For many years, 10Mbit/s Ethernet satisfied the needs of most LAN users. However, during the 1990’s a growth of computing power amongst other things brought around the need for more network capacity. At the same time, Ethernet was up-rated to operate at 100Mbit/s also known as Fast Ethernet.
8 Gigabit Ethernet – 1Gbit/s Ethernet Gigabit Ethernet is the next evolution from 100Mbit/s Fast Ethernet. Essentially it is simply Fast Ethernet yet ten times faster. However, as a consequence of this increased operating speed, a number of issues can result. While these issues are very much implementation dependent, techniques have been built in to Gigabit Ethernet to circumvent them. This section looks at how Gigabit Ethernet works, yet also provides an insight into the potential issues of its use as well as the mechanisms designed to overcome them.
Switched Ethernet is used extensively today as a way to bring improved performance to an Ethernet network along with other capabilities such as the ability to extend a LAN across a WAN infrastructure.
10 Spanning Tree with Ethernet switches When creating a switched Ethernet network environment, it is commonly a requirement to implement resilience through the use of redundant paths. Because of the way that Ethernet switches work, this creates the issue of loops where data frames can potentially loop around indefinitely. The standard mechanism used to overcome this loop issue is to use a protocol known as the Spanning Tree protocol.
11 VLANs – Virtual LANs using Ethernet switches VLANs allow specific stations to participate in a LAN (more specifically defined as a broadcast domain) without necessarily being physically attached to the same LAN. This function can be brought about through the use of Ethernet switches.
12 10 Gigabit Ethernet – 10Gbit/s Ethernet Yet again, Ethernet has grown by another order of magnitude. 10Gbit/s Ethernet is ten times faster than Gigabit Ethernet yet still uses the same frame format. It does, however, have some significant differences to previous Ethernet versions, most notably that it will only operate on optical fibre and will only operate in full-duplex mode (meaning that the collision detection mechanisms are unnecessary. Furthermore, in addition to the normal LAN physical interface, 10 Gbit/s Ethernet also has a WAN physical interface (PHY) defined for use across a WAN.
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