Understanding Ethernet LANs
Training Course

HN Networks - We are based in Maidenhead, UK and offer training in ATM, Frame Relay, IP, voice and speech technologies, Ethernet, Voice over IP - VoIP and other telecommunications & datacommunications technologies. This training course is in Understanding Ethernet LANs.

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 as well as into the realms of switching.

This course provides a comprehensive look at Ethernet technologies from the ground up to where things are today. We offer two versions of the course: a one day version giving more of an overview yet still covering the key aspects in reasonable detail, and a two day course where we go into somewhat more depth to most of the subjects.

Course Agenda

The following is an outline of the sections included in the course:

1. Introduction to, Overview of and History of Ethernet
2. Frame Formats - Ethernet V2 and IEEE 802.3
3. CSMA/CD - Carrier Sense Multiple Access / Collision Detection
4. Common Protocols used on Ethernet
5. The AUI Interface
6. 10BASE5 - Thick Ethernet
7. 10BASE2 - Thin Ethernet
8. The Ethernet Repeater
9. 10BASE-T - 10Mbit/s Ethernet over Twisted Pair
10. 10BASE-FX - 10Mbit/s Ethernet over Fibre
11. System Design Considerations for 10Mbit/s Ethernet
12. 100BASE-X - 100Mbit/s Ethernet
13. Bridging
14. Switched Ethernet
15. Routing
16. Using an Ethernet Traffic Monitor and Protocol Analyser
17. Gigabit Ethernet

Course Length

The 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?

• What are LANs and what are they used for?
• The backgound to Ethernet - ALOHA - Xerox, DEC, Intel and Xerox (DIX) and IEEE 802.3

2 Frame Formats - Ethernet V2 and IEEE 802.3

There are two 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. This section looks at both frame types with a look at how the two may be differentiated between and why and what systems/protocols use each type.

• The frame format defined in Ethernet V2 specification
• The frame format defined in IEEE 802.3
• The MAC address - Physical/Unicast, Multicast and Broadcast
• Some general packet related terms - Runt/Fragment, Jabber, Jam, Inter-Packet Gap, Slot-time etc...

3 CSMA/CD - Carrier Sense Multiple Access / Collision Detection

Because Ethernet is fundamentally a shared medium, there is a need to provide a mechanism to arbitrate between different devices accessing the medium. The method used is known as CSMA/CD where a device will listen on the LAN before transmitting and while transmitting, monitors for a collision just in case another device transmits at the same time.

• How CSMA/CD works
• Various causes of collisions

4 Common Protocols used on Ethernet

There are many different protocols that are used on Ethernet LANs. Some are more common than others and some are really quite old and are diminishing in use. This section looks at how different protocols are carried and looks at some of the more common ones including IP (and associated protocols such as TCP and UDP) and IPX (Novell).

• The ISO 7 layer model and how this really relates to LANs
• The Novell suite of protocols - IPX, SPX, NCP and SAP
• The IP suite of protocols - IP, UDP, TCP, ARP and RARP

5 The AUI Interface

The AUI interface is a common type of media-independent interface that can be used to connect to Ethernet LANs. It was the original type used to connect from a Thick Ethernet transceiver to the user device such as PC of fileserver. It is also a common type of interface used today on all kinds of transceiver device including 10BASE5, 10BASE2, 10BASE-T and 10BASE-F.

• The signals used on the AUI interface
• The rules for using AUI

6 10BASE-5 - Thick Ethernet

The original form of 10Mbit/s Ethernet ran on a coaxial cable type of 50 ohm impedance. This was named Thick Ethernet and while not being used to a great extent today still warrants being looked at.

• Encoding on Thick Ethernet - Manchester encoding
• Rules about the use of Thick Ethernet
• How collisions work on Thick Ethernet

7 10BASE2 - Thin Ethernet

10BASE2 - Thin Ethernet used to be a very popular method of implementing an Ethernet LAN. Today it still has its place, although has largely been superceded by UTP cabling.
Encoding on Thin Ethernet.

• Rules about the use of Thin Ethernet
• How collisions work on Thin Ethernet
• Various configurations for Thin Ethernet

8 The Ethernet Repeater

There are various restrictions that limit the physical size of an Ethernet network. These are dependent upon two main factors including delay and attenuation on the media used. In order to increase the size of an Ethernet LAN, some form of active device is necessary. We shall look at other devices including switches, bridges and routers later, however a repeater allows a LAN to be enlarged within what is known as a collision domain.

• What is meant by the term "collision domain"?
• A look at the various functions of a repeater
• Various types of repeaters - 2 port, multi port, modular repeater etc..

9 10BASE-T: 10Mbit/s Ethernet over Twisted Pair

Most Ethernet networks today operate over Unshielded Twisted Pair (UTP) cable. This provides a significant number of benefits over the use of other media types such as coaxial cable. This section looks at how 10BASE-T operates looking at devices known as hubs (basically multi-port repeaters) as well as the way the networks are cabled. We also provide an overview of the performance parameters that the cabling system must meet in order to support Ethernet successfully.

• Introduction to "structured wiring "
• The UTP hub
• The RJ45 interface connector and pins used for Ethernet
• Various UTP cable types - Category 5, 4 and 3. - Standards: ISO 11801, EIA/TIA 568A and TIA TSB-67
• Full duplex operation of 10BASE-T

10 10BASE-FX: 10Mbit/s Ethernet over Fibre

Today there are more and more people considering the use of fibre within the LAN due to its benefits compared with using copper based cable. This section looks at the benefits associated with the use of fibre (and the down-sides) and looks at the standard ways of using it with Ethernet.

• Introduction to fibre - Multi-mode and Single/Mono-mode
• The differences between using fibre and copper based media
• How Ethernet operates on fibre

11 System Design Considerations for 10Mbit/s Ethernet

Very key to a reliable Ethernet network is its design. In order to function correctly, there are various rules that must be followed. Many networks today fail to meet the rules, and while some appear to work most of the time, when they do go wrong (which is usually quite often), those in charge often don't know where to start in order to fix it. Start with a conforming network and things are so much easier! In fact, your LAN probably won't go wrong so often.

• What are the basic criteria for assessing a network design?
• Two rules defined by IEEE 802.3: Rule 1 and Rule 2
• A detailed look at Rule 1 - The 5 - 4 - 3 rule: 5 Segments, 4 repeaters and 3 active segments

12 100BASE-X: 100Mbit/s Ethernet

Network users today are often finding that a 10Mbit/s network is simply not enough to satisfy their demand for bandwidth. There are many issues behind the need for more bandwidth and many ways to solve the problem including such techniques as network segmentation through the use of switches or other devices including bridges and routers. This section, however looks at 100Mbit/s Ethernet also called Fast Ethernet.

• The driving factors for Fast Ethernet
• Fast Ethernet repeaters
• The Media Independent Interface (MII): The 100Mbit/s equivalent of AUI
• 100Mbit/s physical level encoding
• Fast Ethernet design considerations
• A summary of the differences between Fast Ethernet and 10Mbit/s Ethernet
• Full duplex operation of Fast Ethernet

13 Bridging

One of the methods that can be used to segment a LAN is through the use of bridges. There are various types of bridges and methods used to build large bridges networks. This section looks at what bridges are, how they work and some of the issues involved in their use.

• Why bridge?
• What is a bridge?
• How a bridge works
• How Spanning Tree works and why it is used

14 Switched Ethernet

Becoming very popular today is a method known as Ethernet switching. Fundamentally the same as bridging, it works very much faster. This section looks at the benefits behind why you would use switching and looks at various switching techniques.

• Why switch?
• How a switch works
• Cut-through switches
• Interim cut-through switches
• Store and forward switches

15 Routing

Bridging and switching does not always solve the problems behind needing to segment a network. This section discusses the need for routing and looks at how routers work along with providing an understanding of routing protocols.

• Why route?
• Routing protocols - RIP, RIP2, OSPF, IGRP

16 Using an Ethernet Traffic Monitor and Protocol Analyser

If a network doesn't work correctly, it is important to understand why, so that the problem can be fixed. This section takes a hands-on approach to looking at the function of an Ethernet traffic monitor and network analyser. If possible, we will attach our monitor/analyser to your own network and use that as a platform for demonstrating what a monitor/analyser does and how you might use it. Of course, traffic monitors and protocol analysers don't only need to be used during fault situations, they can also be used as proactive network management tools.

• The operation of a traffic monitor
• The operation of a protocol analyser
• How the tool would be used to fault find
• Baselining your network

17 Gigabit Ethernet

We hear a lot today about the need for even more bandwidth and even faster networks. Gigabit Ethernet provides a method for delivering a solution to this need (although, so does 100Mbit/s Ethernet, today). However, it does have its issues. This section looks at how Gigabit Ethernet works, yet also provides an insight into the issues that it creates and also aims to overcome.

• Why Gigabit Ethernet?
• How it works - A look at IEEE 802.3z
• Do we need really need Gigabit Ethernet? - A look at alternatives