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C O U R S E

5 6 5

Networking Technologies
Volume 1

This document should only be used by a Novell-certified instructor.
Ifyouthinkthisdocumentwaspirated,call1-800-PIRATESor1-801-861-7101.
Networking Technologies Instructor Guide (Volume 1)

Education

INSTRUCTOR GUIDE

100-004273-001
Revision 1.0

Proprietary Statement
Copyright © Novell, Inc. 1994, 1997, 1998. All rights reserved.
No part of this publication may be reproduced, photocopied, stored on a retrieval system, or transmitted without the express prior consent of the publisher. This manual, and any portion thereof, may not be copied without the express written permission of Novell, Inc.
Novell, Inc.
1555 North Technology Way
Orem, Utah 84097-2399

Disclaimer
Novell, Inc. makes no representations or warranties with respect to the contents or use of this manual, and specifically disclaims any express or implied warranties of merchantability or fitness for any particular purpose.
Further, Novell, Inc. reserves the right to revise this publication and to make changes in its content at any time, without obligation to notify any person or entity of such revisions or changes.
Further, Novell, Inc. makes no representations or warranties with respect to any
NetWare software, and specifically disclaims any express or implied warranties of merchantability or fitness for any particular purpose.
Further, Novell, Inc. reserves the right to make changes to any and all parts of
NetWare software at any time, without obligation to notify any person or entity of such changes. This Novell Training Manual is published solely to instruct students in the use of
Novell networking software. Although third-party application software packages are used in Novell training courses, this is for demonstration purposes only and shall not constitute an endorsement of any of these software applications.
Further, Novell, Inc. does not represent itself as having any particular expertise in these application software packages and any use by students of the same shall be done at the students’ own risk.

Software Piracy
Throughout the world, unauthorized duplication of software is subject to both criminal and civil penalties.
If you know of illegal copying of software, contact your local Software Antipiracy
Hotline.
For the Hotline number for your area, access Novell’s World Wide Web page at http://www.novell.com and look for the piracy page under “Programs.”
Or, contact Novell’s anti-piracy headquarters in the U.S. at 800-PIRATES (747-2837) or 801-861-7101.

Trademarks
Novell, Inc. has attempted to supply trademark information about company names, products, and services mentioned in this manual. The following list of trademarks was derived from various sources.

Novell, Inc. intraNetWare, NetWare, the N-Design, and Novell are registered trademarks of
Novell, Inc. in the United States and other countries. The NetWare Logotype (teeth logo) is a trademark of Novell, Inc.
CNA and CNI are service marks of Novell, Inc.
CNE is a registered service mark of Novell, Inc. in the United States and other countries. intraNetWare Client is a trademark of Novell, Inc.
NetWare 4 is a trademark of Novell, Inc.
NetWare 5 is a trademark of Novell, Inc.
Novell Application Launcher is a trademark of Novell, Inc.
Novell Authorized Education Center and NAEC are service marks of Novell, Inc.
Novell Directory Services and NDS are trademarks of Novell, Inc.
Novell Distributed Print Services and NDPS are trademarks of Novell, Inc.

Other Trademarks
Adobe is a registered trademark of Adobe Systems Incorporated. Acrobat is a trademark of Adobe Systems Incorporated.
Apple and AppleTalk are registered trademarks of Apple Computer, Inc.
DATASHOW is a registered trademark of Sayett Technology, Inc.
DynaText is a registered trademark of Electronic Book Technologies, Inc.
IBM is a registered trademark of International Business Machines Corporation.
Intel is a registered trademark of Intel Corporation.
Java is a registered trademark of Sun Microsystems Inc. in the United States and other countries.
Macintosh is a registered trademark of Apple Computer, Inc.
Microsoft is a registered trademark of Microsoft Corporation.
OS/2 is a registered trademark of International Business Machines Corporation.
Pentium is a registered trademark of Intel Corporation.
Persuasion is a registered trademark of Adobe Systems Incorporated.
PhoneNet is a registered trademark of Farallon Computing, Inc.
PostScript is a registered trademark of Adobe Systems Incorporated.
UNIX is a registered trademark of X/Open Company, Ltd.
Windows and Windows NT are registered trademarks of Microsoft Corporation.
Windows 95 is a trademark of Microsoft Corporation.
All other products not listed are the property of their respective owners.

Contents

Contents
Preparation and Setup
Audience..................................................................................... IG Prep-1
Prerequisites............................................................................... IG Prep-1
Agenda ....................................................................................... IG Prep-1
Classroom Requirements ........................................................... IG Prep-3
Classroom Setup Instructions..................................................... IG Prep-3
Using Presentation Graphics ...................................................... IG Prep-3
Displaying the Graphics ........................................................ IG Prep-4
Using Acrobat Reader ........................................................... IG Prep-4
Printing the Graphics ............................................................. IG Prep-5
Using Classroom Animations ..................................................... IG Prep-6

Introduction
Introduction ..................................................................................IG Intro-3
Audience......................................................................................IG Intro-3
Prerequisites................................................................................IG Intro-3
Certification Tests ........................................................................IG Intro-3
Relationship to Other Courses in the Curriculum ........................IG Intro-5
Course Overview .........................................................................IG Intro-7

Section 1

Introducing Computer Networking

Introducing Computer Networking .................................................... IG 1-3
Objectives ......................................................................................... IG 1-3
What Is Networking? ........................................................................ IG 1-5
Computing Models and Network Development ................................ IG 1-5
Centralized Computing ................................................................ IG 1-5
Distributed Computing ................................................................. IG 1-7
Collaborative Computing ............................................................. IG 1-7
Client/Server Computing ............................................................. IG 1-9
Client/Network Computing........................................................... IG 1-9
Today’s Computer Networks .......................................................... IG 1-11
Local Area Network ................................................................... IG 1-13
Wide Area Network ................................................................... IG 1-13

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IG TOC-v

Networking Technologies Instructor Guide (Volume 1)

Required Network Elements ........................................................... IG 1-17
Network Services ...................................................................... IG 1-21
Transmission Media .................................................................. IG 1-23
Protocols ................................................................................... IG 1-25
Written Exercise 1-1: Computer Networking Review...................... IG 1-27
Summary ........................................................................................ IG 1-29

Section 2

Network Services

Network Services.............................................................................. IG 2-3
Objectives ......................................................................................... IG 2-3
Common Network Services .............................................................. IG 2-5
File Services ..................................................................................... IG 2-7
File Transfer ................................................................................ IG 2-9
File Storage and Data Migration.................................................. IG 2-9
File Update Synchronization ..................................................... IG 2-13
Written Exercise 2-1: File Services Review .................................... IG 2-17
Print Services ................................................................................. IG 2-19
Providing Multiple Access from Limited Interfaces .................... IG 2-21
Handling Simultaneous Requests (Queuing) ............................ IG 2-23
Distributed Print Services .......................................................... IG 2-25
Sharing Specialized Equipment ................................................ IG 2-25
Written Exercise 2-2: Print Services Review .................................. IG 2-27
Message Services .......................................................................... IG 2-29
Electronic Mail ........................................................................... IG 2-31
Integrated Mail Services ............................................................ IG 2-31
Workgroup Applications ............................................................ IG 2-31
Written Exercise 2-3: Message Services Review ........................... IG 2-33
Application Services ....................................................................... IG 2-35
Specialization of Servers ........................................................... IG 2-37
Scalability and Growth............................................................... IG 2-37
Written Exercise 2-4: Application Services Review ........................ IG 2-39
Database Services ......................................................................... IG 2-41
Distributed Data......................................................................... IG 2-41
Replication................................................................................. IG 2-43
Written Exercise 2-5: Database Services Review .......................... IG 2-47

IG TOC-vi

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Contents

Centralized versus Distributed Network Services........................... IG 2-49
Control of Resources................................................................. IG 2-49
Server Specialization................................................................. IG 2-51
Choice of Network Operating Systems ..................................... IG 2-51
Written Exercise 2-6: Designing Network Services ........................ IG 2-53
Summary ........................................................................................ IG 2-57

Section 3

Transmission Media

Transmission Media ......................................................................... IG 3-3
Objectives ......................................................................................... IG 3-3
Introducing Transmission Media....................................................... IG 3-5
Common Computer Network Transmission Media ........................... IG 3-9
Cost and Ease of Installation....................................................... IG 3-9
Capacity .................................................................................... IG 3-11
Attenuation ................................................................................ IG 3-11
Interference and Signal Capture ............................................... IG 3-13
Cable Media .............................................................................. IG 3-13
Written Exercise 3-1: Implementing Cable Media .......................... IG 3-49
Cable Transmission Media Comparison ................................... IG 3-53
Wireless Media .......................................................................... IG 3-55
Written Exercise 3-2: Implementing Wireless Media ...................... IG 3-93
Wireless Transmission Media Comparison ............................... IG 3-97
Written Exercise 3-3: Transmission Media Review ........................ IG 3-99
Summary ...................................................................................... IG 3-103

Section 4

Connectivity Devices

Connectivity Devices ........................................................................ IG 4-3
Objectives ......................................................................................... IG 4-3
Network Connectivity Devices .......................................................... IG 4-5
Transmission Media Connectors ................................................. IG 4-7
Network Interface Boards ............................................................ IG 4-9
Modems..................................................................................... IG 4-15
Repeaters .................................................................................. IG 4-19
Hubs .......................................................................................... IG 4-23
Bridges ...................................................................................... IG 4-27
Multiplexers ............................................................................... IG 4-31

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Networking Technologies Instructor Guide (Volume 1)

Internetwork Connectivity Hardware............................................... IG 4-33
Routers ...................................................................................... IG 4-35
Brouters ..................................................................................... IG 4-39
Channel Service Unit/Digital Service Unit ................................. IG 4-39
Written Exercise 4-1: Connectivity Device Review ......................... IG 4-41
Summary ........................................................................................ IG 4-47

Section 5

Network Protocols and Models

Network Protocols and Models ......................................................... IG 5-3
Objectives ......................................................................................... IG 5-3
Need for Rules.................................................................................. IG 5-5
The OSI Reference Model ................................................................ IG 5-7
Layers.......................................................................................... IG 5-7
Layer Interaction within the Same Stack ..................................... IG 5-9
Layer Interaction between Different Stacks............................... IG 5-11
Layer Data Units........................................................................ IG 5-13
The OSI Model and Protocols ........................................................ IG 5-15
Written Exercise 5-1: Network Protocols and Models Review........ IG 5-17
Summary ........................................................................................ IG 5-19

Section 6

The OSI Physical Layer

The OSI Physical Layer .................................................................... IG 6-3
Objectives ......................................................................................... IG 6-3
OSI Physical Layer ........................................................................... IG 6-5
Connection Types............................................................................. IG 6-9
Point-to-Point Connections........................................................ IG 6-11
Multipoint Connections .............................................................. IG 6-13
Physical Topology .......................................................................... IG 6-15
Bus Topology ............................................................................ IG 6-19
Ring Topology ........................................................................... IG 6-25
Star Topology ............................................................................ IG 6-31
Mesh Topology .......................................................................... IG 6-35
Cellular Topology ...................................................................... IG 6-41
Signaling ......................................................................................... IG 6-47
Signal Encoding ........................................................................ IG 6-47
Digital Signaling .............................................................................. IG 6-49
Measuring a Digital Signal......................................................... IG 6-51

IG TOC-viii

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Contents

Analog Signaling............................................................................. IG 6-53
Amplitude .................................................................................. IG 6-55
Frequency ................................................................................. IG 6-57
Phase ........................................................................................ IG 6-57
Current State Analog Encoding ................................................. IG 6-59
State Transition Analog Encoding ............................................. IG 6-61
Bit Synchronization ......................................................................... IG 6-63
Asynchronous............................................................................ IG 6-65
Synchronous ............................................................................. IG 6-65
Bandwidth Use ............................................................................... IG 6-69
Baseband .................................................................................. IG 6-71
Broadband ................................................................................. IG 6-71
Multiplexing ............................................................................... IG 6-73
Written Exercise 6-1: OSI Physical Layer Review .......................... IG 6-83
Summary ........................................................................................ IG 6-85

Section 7

The OSI Data Link Layer

The OSI Data Link Layer .................................................................. IG 7-3
Objectives ......................................................................................... IG 7-3
OSI Data Link Layer ......................................................................... IG 7-5
Media Access Control ................................................................. IG 7-9
Logical Link Control ..................................................................... IG 7-9
Logical Topology ............................................................................ IG 7-11
Media Access ................................................................................. IG 7-15
Contention ................................................................................. IG 7-19
Token-Passing Systems............................................................ IG 7-23
Polling........................................................................................ IG 7-27
Addressing...................................................................................... IG 7-31
Transmission Synchronization........................................................ IG 7-35
Asynchronous Transmission ..................................................... IG 7-37
Synchronous Transmission ....................................................... IG 7-41
Isochronous Transmission ........................................................ IG 7-45
Connection Services....................................................................... IG 7-47
LLC-Level Flow Control ............................................................. IG 7-49
Error Control .............................................................................. IG 7-53
Written Exercise 7-1: OSI Data Link Layer Review ........................ IG 7-55
Summary ........................................................................................ IG 7-57

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IG TOC-ix

Networking Technologies Instructor Guide (Volume 1)

Section 8

The OSI Network Layer

The OSI Network Layer .................................................................... IG 8-3
Objectives ......................................................................................... IG 8-3
OSI Network Layer ........................................................................... IG 8-5
Addressing........................................................................................ IG 8-9
Logical Network Address........................................................... IG 8-11
Service Address ........................................................................ IG 8-11
Switching ........................................................................................ IG 8-15
Circuit Switching ........................................................................ IG 8-17
Message Switching ................................................................... IG 8-19
Packet Switching ....................................................................... IG 8-23
Route Discovery ............................................................................. IG 8-29
Distance Vector Method ............................................................ IG 8-31
Link-State Method ..................................................................... IG 8-33
Route Selection .............................................................................. IG 8-35
Dynamic Route Selection .......................................................... IG 8-37
Static Route Selection ............................................................... IG 8-37
Connection Services....................................................................... IG 8-39
Network Layer Flow Control ...................................................... IG 8-43
Network Layer Error Control...................................................... IG 8-45
Network Layer Packet Sequence Control ................................. IG 8-45
Gateway Services........................................................................... IG 8-47
Written Exercise 8-1: OSI Network Layer Review .......................... IG 8-49
Summary ........................................................................................ IG 8-51

Section 9

The OSI Transport Layer

The OSI Transport Layer .................................................................. IG 9-3
Objectives ......................................................................................... IG 9-3
OSI Transport Layer ......................................................................... IG 9-5
Address/Name Resolution ................................................................ IG 9-9
Service Requester-Initiated Method .......................................... IG 9-11
Service Provider-Initiated Method ............................................. IG 9-11
Addressing Methods ....................................................................... IG 9-13
Connection Identifier ................................................................. IG 9-15
Transaction Identifier ................................................................. IG 9-15
Segment Development ................................................................... IG 9-17

IG TOC-x

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Contents

Connection Services....................................................................... IG 9-19
End-to-End Flow Control ........................................................... IG 9-21
End-to-End Error Control........................................................... IG 9-21
Segment Sequencing ................................................................ IG 9-23
Written Exercise 9-1: OSI Transport Layer Review ........................ IG 9-25
Summary ........................................................................................ IG 9-27

Section 10

The OSI Session Layer

The OSI Session Layer .................................................................. IG 10-3
Objectives ....................................................................................... IG 10-3
OSI Session Layer.......................................................................... IG 10-5
Dialog Control ................................................................................. IG 10-7
Simplex Dialog .......................................................................... IG 10-9
Half-Duplex Dialog .................................................................. IG 10-11
Full-Duplex Dialog ................................................................... IG 10-13
Session Administration ................................................................. IG 10-15
Connection Establishment....................................................... IG 10-17
Data Transfer .......................................................................... IG 10-17
Connection Release ................................................................ IG 10-17
Written Exercise 10-1: OSI Session Layer Review ...................... IG 10-19
Summary ...................................................................................... IG 10-21

Section 11

The OSI Presentation Layer

The OSI Presentation Layer ........................................................... IG 11-3
Objectives ....................................................................................... IG 11-3
OSI Presentation Layer .................................................................. IG 11-5
Translation ...................................................................................... IG 11-7
Bit Order Translation ................................................................. IG 11-9
Byte Order Translation .............................................................. IG 11-9
Character Code Translation .................................................... IG 11-11
File Syntax Translation ............................................................ IG 11-15
Encryption..................................................................................... IG 11-17
Private Key .............................................................................. IG 11-19
Public Keys.............................................................................. IG 11-19
Written Exercise 11-1: OSI Presentation Layer Review ............... IG 11-21
Summary ...................................................................................... IG 11-23

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IG TOC-xi

Networking Technologies Instructor Guide (Volume 1)

Section 12

The OSI Application Layer

The OSI Application Layer.............................................................. IG 12-3
Objectives ....................................................................................... IG 12-3
OSI Application Layer ..................................................................... IG 12-5
Service Advertisement.................................................................... IG 12-9
Active Service Advertisement.................................................. IG 12-11
Passive Service Advertisement ............................................... IG 12-11
Service Use Methods ................................................................... IG 12-13
OS Call Interception ................................................................ IG 12-15
Remote Operation ................................................................... IG 12-15
Collaborative Computing ......................................................... IG 12-15
Written Exercise 12-1: OSI Application Layer Review.................. IG 12-17
Summary ...................................................................................... IG 12-19

Appendix A
Answers to Section Exercises .............................................................. A-1

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Preparation and Setup

Preparation and Setup
Use this section to help you prepare for and set up the course.

Audience
This course is for anyone who needs a basic understanding of how computer networks operate. It is a beginning technical course for CNE® candidates. It does not provide detailed information on the technical aspects of installing or conﬁguring a network.

Prerequisites
Prerequisite knowledge for this course is a basic understanding of computers. Agenda
This is a 2-day course.

Day 1
Section
Introduction

00:10

Section 1: Introducing Computer
Networking

00:20

Section 2: Network Services

02:00

Section 3: Transmission Media

02:45

Section 4: Connectivity Devices

Revision 1.0

Duration (hrs: mins)

01:15

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IG Prep-1

Networking Technologies Instructor Guide (Volume 1)

Day 2
Section
Section 5: Network Protocols and
Models

00:15

Section 6: The OSI Physical Layer

01:45

Section 7: The OSI Data Link
Layer

01:30

Section 8: The OSI Network Layer

01:00

Section 9: The OSI Transport
Layer

00:30

Section 10: The OSI Session
Layer

00:30

Section 11: The OSI Presentation
Layer

00:20

Section 12: The OSI Application
Layer

IG Prep-2

Duration (hrs: mins)

00:10

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Preparation and Setup

Classroom
Requirements
The following table identiﬁes the basic hardware and software needs for this course. Instructions for classroom setup follow.
Setup

Requirements

Classroom

Level 1 Novell® classroom (see http:// education.novell.com/chaninfo/classreq.pdf) NetWare® Server

No servers are required

Workstations

1 workstation for instructor

Hardware

A Pentium computer with 32 MB RAM

s

Software

s

Connection to a large-screen monitor or other projection device at the front of the classroom s

Windows 95™ or Windows NT®
Workstation operating system

s

Software required for large screen monitor or projection device

s

Software and drivers required for presentation graphics and animations
(detailed later in this section)

Table Prep-1: Classroom Requirements

Classroom Setup
Instructions
Set up your classroom by copying the contents of the instructor’s CD to your workstation’s hard disk.

Using Presentation
Graphics
Each section has corresponding presentation graphics in Adobe®
Acrobat™ PDF format. These graphics can be s Displayed from the instructor’s workstation

s

Printed on laser-quality transparency sheets for use with an overhead projector

The graphics are on the instructor’s CD.

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Networking Technologies Instructor Guide (Volume 1)

Displaying the Graphics
To display the graphics from the instructor workstation, use Adobe
Acrobat Reader and an external display device, such as DATASHOW®.

Using Acrobat Reader
1. Install Acrobat Reader on the workstation. Use one of the following installation ﬁles in the CD’s ACROBAT directory: r For DOS, use ACRODOS.EXE.

r

For Windows 3.1, use ACROREAD.EXE.

r

For Windows 95, use ACRORD32.EXE.

You can also download the Installation ﬁles from the Adobe home page at http://www.adobe.com.
2. After installing the Reader, read the README.TXT ﬁle for instructions on using your version.
3. For best results, set your monitor’s resolution to 800 x 600 pixels.
Otherwise, some colors and text will not be displayed clearly.
4. To display the graphics, r From Windows. To display a PDF ﬁle, double-click the ﬁlename.
This starts Acrobat and the ﬁrst graphic for the section appears in full-screen view.

r

From Acrobat. In the main menu, select File | Open and then browse for and select the ﬁle.

5. To move between graphics, r Scroll through the graphics by pressing Enter and the Up-, Down-,
Right-, or Left-arrow keys.
Use the Up- and Right-arrow keys to scroll forward; use the Downand Left-arrow keys to scroll backward.

r

To go to a speciﬁc graphic, press Ctrl+5, type the graphic number, and press Enter.
Do not use F5 in place of the 5 key.
For example, if you are displaying the PDF ﬁle for Section 5 and you want to display the third graphic, press Ctrl+5, type 3, and press
Enter.

6. Close a PDF ﬁle by pressing Esc.

IG Prep-4

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Preparation and Setup

Printing the Graphics
You must have the following: s s

A PostScript® printer with at least 2 MB RAM.
A PostScript driver. (Windows® 95 comes with a PostScript driver.
PostScript drivers can be downloaded from http://www.adobe.com.)

Printing from Windows
1. Open the CD directory and highlight the PDF ﬁle for a course section.
2. To ensure that the graphics print completely on 8.5” x 11” output, scale the print size to 95% (or smaller if necessary).
3. In the menu, select File | Print.
You can print graphics by page number or you can print all graphics in the ﬁle.
4. For each section you want to print, repeat Steps 1, 2, and 3.

Printing from Acrobat Reader
1. From an open PDF ﬁle, press to reduce the display to normal view. The Acrobat menu bar appears at the top of the screen.
2. To ensure that the graphics print completely on 8.5” x 11” output, scale the print size to 95% (or smaller if necessary).
3. In the menu, select File | Print.
You can print the graphics by page number or you can print all graphics in the ﬁle.

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Networking Technologies Instructor Guide (Volume 1)

Using Classroom
Animations
The animations supplied with this course require a 486/50 PC that can display a minimum of 256 colors. To use the animations, do the following:
1. Launch the animation.
The Novell logo appears.
2. Choose from the following: r To move to the title screen, click the mouse.

r

To advance to the animation menu, from the title screen click the mouse. r

To view an animation, click a menu item.
After the animation loads, it pauses to allow you to explain what occurs during the animation.

r

Control the animation by using the standard control bar, shown in
(ﬁg):
To begin an animation, click Play.
To rewind an animation, click Rewind.
To pause an animation, click Pause.
To return to the main menu, click Menu.

3. Exit the animation from the main menu screen by clicking Exit.

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1

Introduction
0

Introduction

Introduction
Duration

Revision 1.0

00:15

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Networking Technologies Instructor Guide (Volume 1)
0
0

Introduction
This course introduces the basic concepts, processes, and rules used in designing and implementing large and small computer networks.

Audience
Networking Technologies, Volume 1, is for anyone who needs a basic understanding of how computer networks operate. It is designed as a beginning technical course for CNE® candidates preparing for Volume 2 of this course. It is not intended to provide detailed information on the technical aspects of installing or conﬁguring a network.

Prerequisites
Prerequisite knowledge for this course is a basic understanding of computers. Certiﬁcation Tests
This course helps you prepare for the following certiﬁcation tests: s CNE 050-632

s

CNI 050-832

Arrange to take the certiﬁcation test for this course within six weeks of acquiring the course materials. Thereafter, the test can be replaced by one based on an updated version of the course.

Intro-1

IG Intro-2

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Introduction

Notes

Presentation

Introduction

Introduction

u

Introduce yourself and the students. u

Explain how you like to handle questions and comments (during sections or after).

s

Explain the location of bathrooms, drinking fountains, etc.

s

Remind students to turn off their cell phones, pagers, etc. s

Familiarize students with their surroundings and their materials. Determine if students have hearing, vision, or other problems. s

u

s

Point out the Reader Comments form at the back of the student manual (and instructor guide).

Introduce the course.

Audience

u

Describe the audience.

Find out what students expect from the course.

Prerequisites

u

Explain the prerequisites.

Assess the knowledge of the students regarding the information to be covered.

Certification Tests

u

Revision 1.0

Mention the tests related to this course.
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Networking Technologies Instructor Guide (Volume 1)
0
0

Relationship to Other
Courses in the
Curriculum
This course is one of ﬁve courses in the NetWare 5TM curriculum. These courses teach network administrator responsibilities. The following table provides brief descriptions of each course in the NetWare 5 curriculum.
Course

Responsibilities
Description

529 NetWare 4.11 to
NetWare 5 Update

Upgrade and migrate to NetWare 5.
Manage the NetWare server using Java® utilities.
Set up DHCP, DNS, and Web servers.
Manage client workstations by managing the workstations remotely, conﬁguring NDS for the Novell Application LauncherTM, and conﬁguring workstations with Workstation Manager.
Manage Novell Distributed Print ServicesTM.

560 NetWare 5
Administration

Manage, protect, organize ﬁle system.
Set up and manage basic network services: create users, set up security, manage printing, and manage workstations.
Install NetWare 5.

565 Networking
Technologies, Volumes
1 and 2

Understand the basic operation of computer networks.
Understand the Open Systems Interconnection (OSI) reference model and how it relates to NetWare.
Understand networking protocols such as TCP/IP and IPX/SPXTM.

570 NetWare 5
Advanced
Administration

Upgrade to NetWare 5.
Conﬁgure the server, NDSTM, and the ﬁle system.
Manage the NDS database, manage a diverse network, and tune the server.
Set up and manage TCP/IP portions of the network such as Web servers,
DHCP, and DNS.

575 NDS Design and
Implementation

Work as a design project team on a case company. Create a design document for NDS and create an implementation schedule for the case company.
Implement the NDS design.

580 Service and
Support

Install and maintain network hardware, including network boards, cables, and storage devices.
Troubleshoot problems with the server, workstations, network, and printing.
Table Intro-1: NetWare 5 Course Descriptions

Intro-2

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Presentation

Notes
Introduction

Relationship to Other Courses in the Curriculum

u

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Explain the relationship of the course to the curriculum.

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Course Overview
Upon completion of this course, students should be able to do the following: 1. Identify the characteristics of the common computing models, the types and functions of the entities required to implement them, and the way network services are delivered in computer networks.
2. List the services that can be implemented on a network.
3. List transmission media and describe their strengths and their weaknesses. 4. List network and internetwork connectivity devices.
5. Describe the need for rules and explain how the OSI reference model can be used to categorize networking concepts.
6. Describe the OSI Physical layer and its purpose.
7. Describe the OSI Data Link layer and its purpose.
8. Describe the OSI Network layer and its purpose.
9. Describe the OSI Transport layer and its purpose.
10. Describe the OSI Session layer and its purpose.
11. Describe the OSI Presentation layer and its purpose.
12. Describe the OSI Application layer and its purpose.

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Introduction

Presentation

Notes
Introduction

Course Overview

u

Briefly describe what is covered in the course.

u

Provide a course agenda.

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Indicate daily starting time, breaks, lunch time, etc.

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Notes

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Introducing Computer Networking
0

SECTION 1

Introducing Computer Networking

Duration

00:30

Computer
Networking

Preparation
Divide students into groups.

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SECTION 1

Introducing Computer Networking
This section introduces concepts associated with computer networks.
The basic terms and concepts deﬁned in this section are used throughout this course.

Objectives
Upon completing this section, you should be able to
1. Deﬁne computer networking.
2. Contrast the features of the computing models.
3. Compare local area network (LAN) and wide area network (WAN).
4. Identify the three basic networking elements, and describe the roles of clients, servers, peers, transmission media, and protocols in delivering network services.

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Notes

Presentation

Introducing Computer
Networking

Introduce the section.

u

(Optional) Organize the class into small workgroups using the business scenario company names used throughout this course.

Computer
Networking

u

The companies include s First Street Fabrics

s

ABC Chemical Corporation

s

Modern Information Services

s

Downtown Fast Foods

Objectives

u

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What Is Networking?
Networking is the sharing of information and services. Computer networking provides the communication tools to allow computers to share information and abilities.

Computing Models and
Network Development
Computer networking technologies are based on the following computing models: s Centralized computing

s

Distributed computing

s

Collaborative computing

In addition, the following computing models are used to categorize the way networking services are provided: s Client/server

s

Client/network

Centralized Computing
In the centralized computing model, large centralized computers, called mainframes, were used to store and organize data. People entered data on mainframes using “local” devices called terminals.
A terminal incorporated an input device, such as a keyboard, with some communication hardware so that a single mainframe could service requests from multiple remote terminals.
In centralized computing, the mainframe provides all the data storage and computational abilities; the terminal is simply a remote input/output device. Computer networks were created when organizations began to require that mainframes share information and services with other mainframes.

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Presentation

Notes

What Is Networking?

Ask the students to define networking. Begin with a generalization, then narrow the definition to computer networking.

u

Define networking.

Networking is the sharing of information and services.

Computing Models and
Network Development

u

Introduce the computing models: s

Centralized

s

Distributed

s

Collaborative

Centralized Computing

u

Describe the centralized computing model: s s

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Mainframe
Terminals

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Computer
Networking

u

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0

Distributed Computing
In distributed computing, personal computers (PCs) have their own processing capabilities.
In the distributed computing model, the application is divided into tasks, and each task is assigned to a computer for processing. The results of the processing can be sent as data to other computers.
For example, in a distributed computing environment, a client accesses a database via the user interface (UI) running on the workstation. The database engine, running on the server, produces the requested reports.

Collaborative Computing
Collaborative computing (also called cooperative processing) is a type of distributed computing using networked computers that “collaborate” by sharing processing abilities.
In the collaborative computing model, two or more computers can share the same task. Collaborative computing allows computers to request processing resources from other computers as needed.

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Notes

Presentation

Distributed Computing

u

Describe the distributed computing model.

The distributed computing model involves
Using multiple computers with processing capabilities s

Splitting tasks between independent computers

s

Collaborative computing is a form of distributed computing. s

Both use networked computers with processing capabilities. Both divide applications into tasks.

s

Distributed computing assigns each task to a single computer. s

Collaborative computing allows tasks to be shared by computers as needed.

Collaborative Computing

u

Describe the collaborative computing model.

u

Stress the distinction between distributed and collaborative computing.

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Computer
Networking

s

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Client/Server Computing
In the client/server computing model, several clients (PCs) are connected to a server (PC). In the client/server model s Processing capabilities are distributed across multiple machines.

s

Clients request services from servers.

s

The server performs some of the processing for the client.

Applications used in a client/server network can be split into a front end that runs on the client and a back end that runs on the server.
In the client/server model, the following can be used: s s

A database application that provides a client interface for requests and a search engine on the server that locates records stored on one or more servers

s

x

Standalone (non-networked) applications such as a spreadsheet program or a word processing program that runs on the client, but saves its data on the server

Programs, such as an email system, that use the server to share information The ﬁve computing models are used to describe how network computing can be accomplished. Many applications are implemented as hybrids, using features of more than one model to accomplish their tasks.

Client/Network Computing
In the client/network computing model, users log in to a network and connect to a set of services rather than to a speciﬁc server. These services can be provided through a directory services approach such as
Novell Directory ServicesTM (NDSTM).

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Introducing Computer Networking

Presentation

Notes

Client/Server Computing

u

Describe the client/server model. Computer
Networking

Client/Network Computing

u

Revision 1.0

Describe the client/network model. Briefly describe the role of NDS in a client/network computing environment.

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Today’s Computer
Networks
Computer networks include computers and computer operating systems associated with all the computing models. A typical network includes mainframes, personal computers, and a variety of other computers and communication devices.
Computer networks are often classiﬁed by size, distance covered, the type of media used, or structure. Even though the distinctions are rapidly fading, the following network classiﬁcations are commonly used: s Local area network (LAN)

s

Wide area network (WAN)

LAN

WAN

Figure 1-1: Computer Network Classiﬁcations

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Presentation

Notes

Today’s Computer Networks

d

1-1 (Figure 1-1: Computer
Network Classifications)

Explain that today’s computer networks typically involve elements of all computing models.

u

Computer
Networking

u

Ask the students what type of networks their companies operate.16 Revision 1.0

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Local Area Network
A local area network (LAN) refers to a relatively small group of connected computers. LANs normally do not exceed tens of kilometers in size and provide data transmission services for a single entity, such as a company, a department, or a university.
A LAN is normally contained within a building or campus and typically uses communication links that are owned and maintained by the group whose data the LAN carries. LAN transmission speeds are often measured in megabits per second (mbps).

Wide Area Network
A wide area network (WAN) comprises multiple LANs.
WANs interconnect LANs which may be at opposite sides of a country or located around the world. WANs often use telephone or satellite communications. Access to WAN links is often leased from a WAN services vendor who is responsible for maintaining the communication equipment. For most WAN links, the transmission speed attainable over the available bandwidth is measured in kilobits per second (kbps).
A special designation has also been given to two speciﬁc WAN categories: enterprise and global.
An enterprise network connects all LANs of a single organization. The term is normally used for networks connecting extremely large organizations, or for networks that cross regional or international boundaries. 1-6

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Presentation

Notes

Local Area Network

u

Describe LANs.

Computer
Networking

Wide Area Network

u

Describe WANs.

u

Define enterprise network.

Revision 1.0

An enterprise network is a WAN that connects all of a single organization’s LANs.

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A global network is one that spans the earth. Global networks might not cover the entire globe, but they cross multiple national boundaries and can include the networks of several organizations. The Internet is a good example of a global network.

Figure 1-2: Enterprise and Global Networks

1-7

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Presentation

Notes

Wide Area Network (continued)

d

Revision 1.0

Define global network.

A global network is a type of WAN that spans the globe
(or crosses multiple national boundaries) and may include the networks of several organizations.

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Computer
Networking

u

1-2 (Figure 1-2: Enterprise and Global Networks)

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0

Required Network
Elements
All networks require the following elements: s s

A method or pathway for contacting each other

s

x

Individuals who need to share something

Communication rules so that two or more individuals can communicate The distinction between having a contact or communication pathway and communicating is an important one. When you have a pathway to contact another individual, you might be heard but not understood. When you communicate with other people, you reach a mutual understanding.

Volume 1 of this course covers the following basic elements of computer networks (see Figure 1-3): s Something to share–Network Services (Section 2)

s

A pathway for contacting others–Transmission Media (Sections 3 and 4)

s

The rules for communication–Protocols (Sections 5 through 12)

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Presentation

Notes

Required Network Elements

u

Identify the three basic elements of networking:

s

Pathway for contact

s

Revision 1.0

Something to share

Communication rules

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s

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These three elements are used throughout this course to group networking technologies and concepts. They are brieﬂy described in this section and used again in Sections 2, 3, and 5.

Section 1

Section 2

Connectivity Devices

Section 5

Network Protocols and Models

Section 6

The OSI Physical Layer

Section 7

The OSI Data Link Layer

Section 8

The OSI Network Layer

Section 9

Presentation

Transmission Media

Section 4

A

Network Services

Section 3

Application

Introducing Computer Networking

The OSI Transport Layer

Section 10

The OSI Session Layer

Section 11

The OSI Presentation Layer

Section 12

The OSI Application Layer

Session
Transport
Network
Data Link
Physical

Figure 1-3: Course Map

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Introducing Computer Networking

Presentation

Notes

Required Network Elements
(continued)

d

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Computer
Networking

u

1-3 (Figure 1-3: Course Map)

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Network Services
Network services are the capabilities that networked computers share.
Network services are provided by numerous combinations of computer hardware and software. Depending upon the task, network services require data, input/output resources, and processing power to accomplish their goals.
In this course, the term service provider refers to the hardware and software combination that fulﬁlls a speciﬁc service role. Computers and other network devices can provide different services or ﬁll multiple roles simultaneously. A service provider is not a computer; it is a subset of the computer’s software and hardware.
You might understand computer networking better if you view a service provider–made up of software and hardware–as an individual that performs a task or role for service requesters.
In the computer industry, a distinction is often made between the following three types of service providers and requesters: s Servers are classiﬁed as service providers. They only provide services. s

Clients are classiﬁed as service requesters. They only request services. s

Peers can be classiﬁed as both a service requester or provider. They provide and request services.

Depending on what software is running, a single computer can simultaneously act as a client, a server, and a peer. Software determines the computer’s limitations and therefore its role as a client, server, or peer. However, most computers ﬁll only one role at a time.
Computer networks are often classiﬁed as one of the following types: s Peer-to-peer

s

Server-centric

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Presentation

Notes

Network Services

Define network services.

u

Point out that a single computer can act as a server, client, and peer simultaneously. Revision 1.0

Network services and computers or nodes do not always exhibit a one-to-one relationship.

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Peer-to-Peer Networks
Peer-to-peer networks allow any entity to both request and provide network services. Peer-to-peer network software is designed so that peers perform the same or similar functions for each other.

Server-Centric Networks
Server-centric networks involve strictly deﬁned roles. By deﬁnition, a server-centric network places restrictions upon which entity can make requests or service them.

x

The speciﬁc services that are offered by network service providers will be discussed in Section 2, “Network Services.”

Transmission Media
Transmission media is the pathway networked entities use to contact each other.

Microwave

Ring

Bus

Star

Figure 1-4: Pathway for Communication

Computer transmission media includes cable and wireless technologies that allow networked devices to contact one another. Transmission media cannot guarantee that other network devices will understand a message. It can, however, guarantee a message delivery path.

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Presentation

Notes

Peer-to-Peer Networks

u

Define peer-to-peer networks. Peer-to-peer networks allow any entity to both request and provide network services.
Computer
Networking

Server-Centric Networks

u

Define server-centric networks. u

Point out that Novell
NetWare is a server-centric network operating system.

Server-centric networks restrict workstations to the role of service provider or requester.

Transmission Media

d

1-4 (Figure 1-4: Pathway for
Communication)

u

Define transmission media.

u

Emphasize the following: s s

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Protocols
Protocols are the rules required to help entities communicate with or understand each other.
A protocol can be one rule or a complete set of rules and standards that allow different devices to hold conversations.

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Presentation

Notes

Protocols

u

Define protocols.

Protocols are the rules required to help entities communicate or understand each other.
Computer
Networking

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Written Exercise 1-1:
Computer Networking
Review
Answer the following questions.
1. What are the three basic elements in networking?

2. Match the following terms with the description by placing the letter of the description in front of the appropriate term.
Term

Description

Centralized Computing

A. Multiple computers are dispersed throughout an organization to perform individual computations and data storage tasks.

Distributed Computing

B. Computers access network services without logging in to a speciﬁc service provider.

Collaborative
Computing

C. Applications are divided into a front end for user input and a back end for providing the requested service.

Client/Server
Computing

D. Multiple computers cooperate to perform the same task.

Client/Network
Computing

E. A mainframe provides all the data storage and computational abilities.

3. Compare LANs and WANs.

4. Deﬁne the term protocol. How are protocols used in computer networks? 1-13

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Presentation

Notes

Written Exercise 1-1:
Computer Networking Review

u

u

Computer
Networking

a

:10

Introduce the exercise.

Have students complete
Exercise 1-1.

Review the answers to
Exercise 1-1.

Answers:
1. First, at least two individuals who have something to share. Second, a pathway for one individual to contact another. Third, rules so that two or more individuals can communicate. 2. Centralized = E
Distributed = A
Collaborative = D
Client/Server = C
Client/Network = B
3. A LAN is normally contained within a building or campus. Transmission speeds are measured in
Mbps, and LAN hardware is maintained in-house.
A WAN interconnects LANs. It covers a large geographic distance, often requires the use of service providers who maintain the hardware, and typically uses transmission speeds measured in kbps. 4. Protocols are the rules required to help entities communicate with or understand each other. To communicate, networked computers must use the same or compatible protocols, or they must use a device that translates their disparate protocols.

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Summary
Computer networking has become increasingly important in today’s global marketplace. Today LANs and WANs are common informationsharing tools that help people communicate using their computers.
Computer networks require the following: s At least two individuals who have something to share

s

A method or pathway (transmission media) for contacting each other

s

Rules (protocols) so that two or more individuals can communicate

Acting as clients, servers, and peers, computers can provide the information and service exchange required by their users.

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Introducing Computer Networking

Presentation

Notes

Summary

u

Summarize the section.

Review the objectives and answer questions.
Objectives:

2. Contrast the features of the computing models.
3. Compare local area network (LAN) and wide area network (WAN).
4. Identify the three basic networking elements, and describe the roles of clients, servers, peers, transmission media, and protocols in delivering network services.

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Computer
Networking

1. Define computer networking.

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Notes

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2

Network Services
0

SECTION 2

Network Services

Duration

02:00

Preparation
None

Network Services

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SECTION 2

Network Services
In this section, you learn about the following network service topics: s Common network services (ﬁle, print, message, application, and database) s

Centralized and distributed network services

Objectives
Upon completing this section, you should be able to
1. Identify the functions and features of the ﬁve basic network services.
2. Determine when network ﬁle services should be implemented.
3. Determine when network print services should be implemented.
4. Determine when network message services should be implemented.
5. Determine when network application services should be implemented. 6. Determine when and how network database services should be implemented. 7. Identify how the delivery of individual network services is affected by centralized and distributed network architectures.

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Network Services

Presentation

Notes

Network Services

u

Introduce the section.

Objectives

u

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Common Network
Services
Computer applications require some combination of data, processing power, and input/output resources to accomplish their tasks. Network services allow computers to share these resources using special network applications.
Many of the applications that provide network services are combined into a single network operating system (NOS). Network operating systems are speciﬁcally designed to coordinate and provide multiple network services to other computer applications.

x

Local or desktop operating systems (OS) are the computer code that manages the computer’s resources (CPU, memory, peripherals, and so on). DOS, Windows 95, OS/2™, and UNIX™ are all examples of local operating systems.
A network operating system (NOS) is a specialized operating system that performs resource management tasks for multiple service requesters by coordinating the sharing of services on the network.
An OS typically resides on a single computer; a NOS can be distributed throughout many computers on the network. Novell NetWare™ is the most widely used LAN NOS.

This subsection deﬁnes the following common network services: s File services

s

Print services

s

Message services

s

Application services

s

Database services

Each subsection provides a basic deﬁnition of each service and presents the functions and other aspects associated with the service.

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Network Services

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Notes

Common Network Services

u

Describe network applications and operating systems as the providers of network services.

u

Emphasize the following points about network services: s

s

u

Network services are provided by special applications invisible to the computer user.
These applications are usually part of a network operating system.
NOSs (and network applications) perform their tasks as background processes. List several network services discussed in this section: s

Print services

s

Message services

s

Application services

s

Revision 1.0

File services

s

u

Network Services

s

Database services

Introduce the section activity. Upon completion of this section, students will be required to present solutions to various scenarios as part of their business group.

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File Services
File services include network applications designed to store, retrieve, or move data ﬁles. File services perform the following: read, write, access control, and data management.
Network ﬁle services help you s Rapidly move ﬁles from place to place

s

Back up critical data

s

Use storage hardware efﬁciently

s

Manage multiple copies of the same ﬁle

The functions included with network ﬁle services deﬁne actions and tasks associated with this particular service.
Network ﬁle service functions include s File transfer

s

File storage and data migration

s

File update synchronization

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Notes

File Services

Define file services.

u

Describe the user benefits of network file services.

u

Mention that file services is one of the most common network services.

u

List the file service functions that will be discussed. s s

s

Revision 1.0

Network Services

u

File transfer
File storage and data migration File update synchronization This document should only be used by a Novell-certified instructor.
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File Transfer
File transfer refers to any service that saves, retrieves, or moves ﬁles for a network client. This service allows you to handle data much more efﬁciently. For example, suppose that your organization owns several buildings located in different parts of your city. If you were to personally transport a ﬁle, on a ﬂoppy diskette, from one building to another, it might take you hours. You could save some time and money using a postal service, but the delay involved in shipping storage media is still relatively high. A network ﬁle service, however, can move that same ﬁle electronically to multiple recipients across a computer network in a matter of seconds.
File transfers can be performed with relative ease regardless of file size, distance, and often even the local operating system.

File Storage and Data
Migration
Computers store data on a variety of magnetic and optic disks, diskettes, and tapes. Each storage medium exhibits characteristics that make it suitable for a speciﬁc use: s Online storage media, such as hard disks, are immediately available to the computer.

s

Nearline storage media, such as tape carousels, CD-ROM jukeboxes, and so on, are not immediately available to the computer, but do not require human intervention.

s

Ofﬂine storage media, such as removable tape cartridges, require human intervention before they become available to the computer.

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Network Services

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Notes

File Transfer

u

Describe the file transfer function. File Storage and Data Migration

Revision 1.0

Discuss the storage media and their specific uses.

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u

IG 2-9

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Online Storage
(For Example, “Hard Disk”)

Nearline Storage
(For Example, “Tape Jukebox”)

A

Offline Storage
(For Example,
“Removable Storage”)

Figure 2-1: Online, Nearline, and Ofﬂine Storage Media

Because the efﬁcient use of each storage device requires continuous management of multiple devices, network applications are well suited to control data storage activities on different storage systems.
Using ﬁle storage and data migration functions, all networked computers can take advantage of the data storage device that is appropriate for their access time, reliability, and longevity needs.
As data ages and becomes less used, it can be moved from expensive online hard disk drives to less expensive and longer-life ofﬂine storage media. This is called ﬁle archiving or backup.

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Network Services

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Notes

File Storage and Data Migration
(continued)

d

2-1 (Figure 2-1: Online,
Nearline, and Offline Storage
Media)

Describe the file archiving function. u

Mention the data storage and migration features of
Novell NetWare.

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u

IG 2-11

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File Update Synchronization
The business workplace is increasingly dependent on mobile computing devices such as laptop computers and hand-held personal productivity devices. If you need access to a ﬁle that is stored on a network server, you can save a copy of the ﬁle to your computer’s hard disk to ensure that it will be accessible when the connection is not available.
Since the ﬁle now exists in two places, someone else might access and change the original ﬁle. If this occurs, your copy becomes out-of-date.
Similarly, if you modify your copy, the original on the network ﬁle server is outdated.
A ﬁle service called ﬁle update synchronization is one way to identify changes and manage the process of updating the ﬁle to ensure its integrity. File update synchronization compares the time and date corresponding ﬁles were saved to determine which is most current. It can also keep track of who has a speciﬁc ﬁle and if intermediary changes have been made. File Server

File A
Date: 12/10/98

Newer file found. Update?

Laptop
File A
Date: 12/08/98
Figure 2-2: File Update Synchronization

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Notes

File Update Synchronization

u

d

Revision 1.0

When mobile computing devices duplicate files, they need to coordinate file checkout, to recognize when changes have occurred, and to take the appropriate action. 2-2 (Figure 2-2: File Update
Synchronization)
Network Services

u

Describe the need for file update synchronization.

Define file update synchronization. This document should only be used by a Novell-certified instructor.
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Most ﬁle update synchronization software monitors speciﬁc ﬁles and compares the time and date the different copies of the ﬁles were saved to determine which is most current.

x

What if two copies were changed? File update synchronization should be able to read the information contained in similar ﬁles and intelligently combine the changes. However, current ﬁle update synchronization schemes can only notify you of potential conﬂicts.
If you want to save changes from both ﬁles, you need to combine the ﬁles yourself. The network ﬁle service only tells you that two different versions exist. 2-7

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Network Services

Presentation

Notes

File-Update Synchronization
(continued)

u

Point out the note on the student page.

Network Services

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Written Exercise 2-1:
File Services Review
Answer the following questions.
1. Deﬁne ﬁle services.

2. Which two functions are considered part of ﬁle services? (Choose two.) a. File transfer
b. Nomadic storage
c. Backup
d. Data centralization
3. Describe ﬁle transfer.

4. Describe ﬁle update synchronization.

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Network Services

Presentation

Notes

Written Exercise 2-1:
File Services Review

u

a

:10

u

Introduce the exercise.

Have the students complete
Exercise 2-1.

Answers:
1. File services include all network applications designed to efﬁciently store, retrieve, or move data ﬁles by providing read, write, access control, and data management functionality.
2. a and c
3. Moving data from one storage medium or location to another. 4. A service that compares time and date of corresponding files and automatically updates all file locations with the latest version.

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Network Services

Review the answers to
Exercise 2-1.

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Print Services
Print services are network applications that control and manage access to printers, fax machines, and copy equipment. Print services accept print job requests, interpret print job formats and printer conﬁgurations, manage print queues, and interact with networkable printers and fax equipment for network clients.
Network print services help you s Reduce the number of printers in your organization

s

Place printers for the convenience of your users

s

Store print jobs to reduce the time your computer spends sending a print job

s

Share specialized printers efﬁciently

s

Automate the transmission and reception of fax images

The functions included with network print services deﬁne actions and tasks associated with this particular service.
Network print service functions include s Providing multiple access from limited interfaces

s

Handling simultaneous requests and queuing those requests

s

Distributing print services

s

Sharing specialized equipment

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Network Services

Presentation

Notes

Print Services

Define print services.

u

Describe the user benefits of network print services.

u

List the print service functions that will be discussed: s

s

s

s

Revision 1.0

Print services are network applications that control and manage access to printers and fax equipment.

Network Services

u

Providing multiple access
Handling simultaneous requests Distributing print services
Sharing specialized equipment This document should only be used by a Novell-certified instructor.
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Providing Multiple Access from Limited Interfaces
Typically, only two or three computers can be directly connected to each printer. On the other hand, network print services allow numerous clients to be serviced by a single printer.

Figure 2-3: Network Printing

Reducing the total number of printers can save your organization a substantial amount of money. Having fewer printers reduces the number of devices to buy, maintain, and manage.

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Notes

Providing Multiple Access from
Limited Interfaces

d

2-3 (Figure 2-3: Network
Printing)

Identify aspects of network print services.

u

Emphasize the following: s s

Revision 1.0

Network Services

u

Most modern printers provide a relatively small number of interface ports.

Print services provide multiple access to limited printer interfaces.
Reducing the number of peripheral devices reduces acquisition and maintenance costs.

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Handling Simultaneous
Requests (Queuing)
When two user applications try to send data to a printer at the same time, both applications compete for the printer’s limited ability to accept and store print requests.

Queuing solves this bottleneck problem. A print queue captures and stores computer print jobs. Depending upon each implementation’s speciﬁc features, print queues can hold, prioritize, and manage print jobs. WS1
Print
XYZ.DB

WS4
Print
AZI.Doc

Print Queue
4) ABC.Doc
3) AZI.Doc
2) XYZ.DB
1) EFG.Txt

WS3
Print
EFG.Txt

WS2
Print
ABC.Doc

Printer

Figure 2-4: Print Queuing

When printing with network print services, your application sends print requests and data to what appears to be a printer. These requests are actually routed to a print queue. The print requests remain in the queue until the printer is available.
Network print service providers (print servers) often perform queuing.

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Network Services

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Notes

Handling Simultaneous Requests
(Queuing)

u

d

Revision 1.0

2-4 (Figure 2-4: Print
Queuing)
Network Services

u

Mention that traditional printers can only accept one print job at a time.

Describe queuing.

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Distributed Print Services
Distributed print services offers important improvements over queue-based print services. These improvements include s A centralized, simpliﬁed, single point of administration

s

Information exchange between client and printer

s

Integration with directory services

s

Automatic printer driver download and installation

Because of these improvements, distributed print services helps you get the most out of your printing resources, whether you’re in a small workgroup or an enterprise-wide system.

x

Novell Distributed Print ServicesTM (NDPS) is one implementation of this service. For detailed information regarding NDPS, refer to Course 560,
NetWare 5 Administration.

Sharing Specialized
Equipment
Some printers are designed for speciﬁc use, such as high-speed output, large format paper, or color printing. Specialized equipment can be expensive or infrequently used. By networking each device with numerous clients, you can reduce the effective cost per user and optimize printer use.
Another type of specialized equipment is the network fax. Network fax service allows service requesters to send and receive faxes using a shared fax device.
Network fax devices accept digital input from the network, eliminating the hard copy document scanning required by traditional fax machines.
Advanced network fax devices can route incoming faxes to your computer. You can then view the fax and decide whether to print it.

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Network Services

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Notes

Distributed Print Services

u

Discuss the features of distributed print services.

Sharing Specialized Equipment

Discuss various types of specialized equipment used for printing.

u

Describe network fax service. Revision 1.0

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Network Services

u

IG 2-25

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Written Exercise 2-2:
Print Services Review
Answer the following questions.
1. What are print services?

2. What are the beneﬁts of queue-based network printing services?

3. What are the beneﬁts of distributed printing services?

4. Describe how a network fax service can make faxing documents more efﬁcient. 2-13

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Network Services

Presentation

Notes

Written Exercise 2-2: Print
Services Review

u

a

:10

u

Introduce the exercise.

Have the students complete
Exercise 2-2.

Answers:
1. Print services are network applications that control and manage access to printers and fax equipment.
2. Benefits include the following: r Users share printers.

r

A user does not have to wait for his or her job to print before the application is released to perform other tasks.

r

Fewer printers are required.

3. The same benefits as queue-based printing apply to distributed printing services. Additional benefits include: r

Centralized and simplified administration

r

Bidirectional feedback and control

r

Integration with directory services

r

Automatic printer driver download and installation

4. Network fax devices remove the unnecessary paper-based steps.

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IG 2-27

Network Services

Review answers to
Exercise 2-2.

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Message Services
Message services include storing, accessing, and delivering text, binary, graphic, digitized video, and audio data. Message services deal with communication between computer users, user applications, network applications, and documents.

R,
Q

Text

,,
,,
Graphic

Video

Audio

Figure 2-5: Network Message Services

Network message services help you s Exchange computer-generated notes and ﬁles

s

Integrate electronic mail with voice mail systems

s

Route and share data using workﬂow and linked-object document applications s

Organize and maintain user and device information directories

This subsection describes the following types of message-enabled applications: s

Electronic mail

s

Integrated electronic mail and voice mail

s

Workgroup applications

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Network Services

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Notes

Message Services

d

2-5 (Figure 2-5: Network
Message Services)

Define message services.

u

List the message-enabled applications that will be discussed: s

s

s

Revision 1.0

Network Services

u

Electronic mail
Integrated electronic mail and voice mail
Workgroup applications

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Electronic Mail
Electronic mail, or email, refers to the electronic transfer of message data between two or more networked computers.
Email messages often include a variety of digital text, graphic, video, and audio data. Modern email software must provide the transportation and presentation tools to accommodate the wide variety of data formats.
Contemporary network message services can make independent email routing and delivery decisions when servicing portable clients or responding to network conﬁguration changes.

Integrated Mail Services
Network management systems can be combined with either Email or pager services to alert network administrators when speciﬁc conditions exist on networks or networked devices.
Message services that integrate email and voice mail are also available.
Because voice mail systems are simply specialized computers, they can be incorporated into computer networks.

Workgroup Applications
Message services have also been used to create a new class of applications called workgroup applications. One common type of workgroup application is workﬂow management.
Workﬂow management applications intelligently route forms, notices, and documents among network clients. These service providers handle multiuser, distributed business processes.
Message services are ultimately responsible for making workﬂow routing and delivery decisions.

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Network Services

Presentation

Notes

Electronic Mail

u

Describe electronic mail.

Integrated Mail Services

u

Network Services

Describe how computerized mail services can be integrated. Workgroup Applications

u

Explain that a workgroup application uses message services. u

Describe workflow management and its relationship to message services. Revision 1.0

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IG 2-31

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Written Exercise 2-3:
Message Services
Review
Answer the following questions.
1. List three examples of message-enabled applications.

2. How are message services used with workgroup applications?

3. Describe four beneﬁts that message services provide.

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Network Services

Presentation

Notes

Written Exercise 2-3: Message
Services Review

u

a

:10

u

Introduce the exercise.

Have the students complete
Exercise 2-3.

Answers:
1. Three examples of message-related applications are r Electronic mail

r

Integrated electronic mail and voice mail

r

Workgroup applications

2. Message services are ultimately responsible for making workflow routing and delivery decisions.
3. Network message services help you r r

Integrate electronic mail with voice mail systems.

r

Operate object-oriented software with objects distributed throughout the network.

r

Route and share data using workflow and linked-object document applications.

r

Revision 1.0

Pass computer-generated notes and files between users.

Organize and maintain user and device information directories.

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IG 2-33

Network Services

Review answers to
Exercise 2-3.

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Application Services
Application services are network services that run software for network clients. They are different from ﬁle services because they allow computers to share processing power, not just share data.
Network application services s Coordinate hardware and software to run utilities (or software applications) on the most appropriate platform

s

Increase the capabilities of key hardware without upgrading every computer on the network

Network application service functions include s Specialization of servers

s

Scalability and growth

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Network Services

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Notes

Application Services

Define application services.

u

Describe the user benefits of network application services. u

List the application service aspects that will be discussed: s

u

Revision 1.0

Specialization of server

s

Application services are network services which run software for network clients.

Network Services

u

Scalability and growth

Point out that database services are described later in this section as a specific type of application services.

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Specialization of Servers
Application servers employ specialized equipment and software to increase speed, data integrity, and security.
Typically, application servers have more computing power than user workstations and often use special operating systems that have been optimized to perform a speciﬁc operation.
A client-server database system is one example of an application server.
It is discussed later in this section.
The private branch exchange (PBX) is a specialized computer that provides telephone switching services. Most large organizations have used PBXs to run their telephone systems for years.

Scalability and Growth
Network application services provide organizations with relatively inexpensive upgrade paths. If more computing power is required, only the network application server is upgraded.
For example, assume that you use an extremely complex modeling application and that the application server software currently runs on a minicomputer. As your company grows, the minicomputer becomes overworked and response time gets worse and worse. To improve response times, you simply move the application software to a faster computer, or add another server.
You can improve the processing power of the computer while leaving other client and server computers totally unaffected.

x

The beneﬁts of scalability and growth depend on the ability to use the same operating system on the new computer or the same application on a new operating system.

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Network Services

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Notes

Specialization of Servers

u

Point out that application servers can employ specialized equipment to increase speed, data integrity, and security.

u

Provide examples of server specialization: s

Network Services

s

Client-server database systems are discussed in the next subsection.

Client-server database system Private branch exchange
(PBX)

Scalability and Growth

u

Describe the application services aspects of scalability and growth.

u

Emphasize that application services provide organizations with relatively inexpensive upgrade paths.

u

Point out the note in the student manual.

Revision 1.0

Only the server needs to be upgraded for more computing power.

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IG 2-37

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Written Exercise 2-4:
Application Services
Review
Answer the following questions.
1. What are application services?

2. Which of the two aspects listed below are functions of application services? (Choose two.)
a. Scalability
b. Multiuser documents
c. Server specialization
d. Object-oriented programming
3. A private branch exchange (PBX) on a computer network is an example of what?

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Network Services

Presentation

Notes

Written Exercise 2-4:
Application Services Review

u

a

:10

u

Introduce the exercise.

Have the students complete
Exercise 2-4.

Answers:
1. Application services are network services that run software for network clients.
2. a and c
3. A specialized application server

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IG 2-39

Network Services

Review answers to
Exercise 2-4.

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Database Services
Network database services provide server-based database (data or information) storage and retrieval that allow network clients to control, manipulate, and present data. Database applications that allow clients to request data from these specialized servers are called client-server databases. Client-server database applications divide and optimize the tasks involved in requesting and providing data.
Depending on the design goal (increased transactions per second, reduced network trafﬁc, and so on), the client is given a portion of the tasks involved in formulating the request and processing the response, while database servers typically evaluate incoming requests and return data. Network database services s Optimize the computers that store, search, and retrieve database records s

Control where data is stored geographically

s

Organize data logically between organizational departments

s

Provide data security

s

Reduce database-client access time

The following aspects of network database services are discussed here: s Distributed data

s

Replication

Distributed Data
Network database services use distributed data to achieve seamless data sharing. Control over the pieces of the database is divided among the various departments’ computer systems. This process actually divides the database into smaller parts that can be managed by the department that owns the data.
The database management system is responsible for making the database appear as one logical unit while coordinating changes that occur on various (and often different) computer systems.

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Notes

Database Services

Define database services.

Network database services provide server-based database storage and retrieval functions.

u

Define client-server databases. Client-server database applications divide and optimize the tasks involved in requesting and providing data.

u

Point out that the client is given a portion of the tasks involved in formulating the request and processing the response. u

Point out that database servers typically evaluate incoming requests and return data.

u

Describe the user benefits of network database services. Network Services

u

Distributed Data

u

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For example, users can generate reports that contain data from departments other than their own. Reports might include data that is owned by the Sales department.

Replication
Data can typically be retrieved much more rapidly from local databases than from remote databases. Therefore, it is often more efﬁcient for users to work on a local copy of the data. Replication creates and synchronizes multiple copies of a database over the network.
Replication provides fault tolerance (the ability to recover from component failure). If one replica of a database becomes unavailable because of hardware or software failure, the data can be retrieved from another replica.
However, when more than one copy of a database exists, organizations run the risk of making decisions based on out-of-date or incorrect information. Consequently most database software that allows data replication also includes a method of synchronizing the replicas.
Replica

Replica
Local
DB

Replica

2
2

1

1

Local
DB

Change

Master
1

Change

Local
DB

Figure 2-6: Distributed Database Replication Methods

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Notes

Distributed Data (continued)

u

Emphasize how network database services achieve seamless data sharing.

They divide control over the pieces of the database among various computer systems.

Replication

Describe the aspects of replication. u

Network Services

u

Emphasize that replication is used to create and synchronize multiple copies of a database over the network. d

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2-6 (Figure 2-6: Distributed
Database Replication
Methods)

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Currently, most database software uses two different methods to synchronize replicated data. These methods are described below: s Master Database Replication
The master database is the repository of all additions and changes.
The database management system is responsible for making sure that the changes recorded in the master are sent to all copies of the database. Some implementations only allow changes to be made to the master, limiting users to read-only access to other replicas.
Even if users are allowed to make changes to the data in a replica, those changes are ﬁrst sent to the master, which then distributes the changes to the other replicas.

s

Local Database Replication
This method gives several local databases responsibility for recording adds and changes. In addition, the local portion of the management system must then coordinate adds and changes with all the other copies.
This replication method requires all replicas to maintain communication with all other replicas.

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Replication (continued)

u

Continue to describe the aspects of replication.

Network Services

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Written Exercise 2-5:
Database Services
Review
Answer the following questions.
1. Deﬁne network database services.

2. Which two allow multiple copies of all or part of a database to exist?
(Choose two.)
a. Distribution
b. Replication
c. Specialization
d. Multimedia
3. Describe client-server database applications.

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Notes

Written Exercise 2-5:
Database Services Review

u

a

:10

u

Introduce the exercise.

Have the students complete
Exercise 2-5.

Answers:
1. Network database services provide server-based database storage and retrieval functions.
2. a and b
3. Client-server database applications divide and optimize the tasks involved in requesting and providing data.

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Network Services

Review answers to
Exercise 2-5.

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Centralized versus
Distributed Network
Services
When you decide to implement a computer network, you must decide whether network services should be centralized, distributed, or some mixture of both.
Conceptually, distinct computers provide different network services. In reality, network services can be combined on a single computer or small group of computers (using a server-centric NOS) or distributed to all the computers on the network (using a peer-to-peer NOS).
The following issues are involved in making service distribution decisions: s

Control of resources

s

Server specialization

s

Choice of network operating systems

Control of Resources
Because computers fail and computer users ignore security standards, you should consider how network resources can be monitored and controlled. The easiest control strategy involves centralizing all the hardware and software required to service the network into one dedicated group that can be monitored by management applications.
By centralizing the resources, you protect the services offered and determine which computer will support a particular network service.
In contrast, when you distribute control, you allow many different computers to provide multiple services. When a service operates incorrectly in a distributed architecture, tracking down the offending party can be difﬁcult.

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Notes

Centralized versus Distributed
Network Services

Introduce centralized versus distributed network services. u

Emphasize that in centralized networks, network services can be combined on one or more computers. u

Emphasize that in distributed networks, network services are distributed to all network computers (using a peer-to-peer NOS).

u

List the centralized versus distributed issues that will be discussed: s Control of resources

s

Combined netowrk services can operate on a single computer or on a small group of computers (using a server-centric NOS).
Network Services

u

Server specialization

s

Network operating system choice

Control of Resources

u

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Describe the issue of control of resources.

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Server Specialization
Server specialization simply means assigning network service roles to speciﬁc computers that have been optimized to ﬁll that role. If you explicitly assign dedicated resources, you are making at least a partial commitment to centralized services.

Choice of Network Operating
Systems
Although an organization can implement a speciﬁc subset of network services and organize them in a centralized or distributed manner, network architectures are often determined by available network operating systems (NOSs).
A server-centric network operating system provides centralized network services from dedicated servers. Server-centric network operating systems include s NetWare and intraNetWare

s

Banyan® Vines

s

Open VMS

A peer-to-peer network operating system provides distributed network services using peers. Peer-to-peer network operating systems include s Windows NT® Server

s

Windows NT Workstation

s

Windows 95TM

s

Windows for Workgroups

s

Apple Computer® AppleTalk®

The line between server-centric and peer-to-peer network operating systems is often ill-deﬁned. For example, because you can use a
Windows NT server as a workstation (service requester), Windows NT is a peer-to-peer network operating system.
However, a Windows NT server can function in either a server-centric or a peer-to-peer environment and typically is implemented as a dedicated server, with its workstation capabilities reserved for network or server management tasks.
In addition, modern networks often use several network operating systems. You should consider interoperability between NOSs when designing and managing LANs and WANs.

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Notes

Server Specialization

u

Review server specialization. u

Emphasize that the explicit assignment of specialized, dedicated resources implies at least partial commitment to centralized services.

Refer to the “Application Services” subsection.

Network Services

Choice of Network Operating
Systems

u

Introduce network operating system choice.

u

Emphasize that network architectures are often determined by available network operating systems.

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Written Exercise 2-6:
Designing Network
Services
In this exercise, each group is assigned a scenario. Each group should s Discuss the assigned scenario within the group.

s

Identify the organizational needs and match a network service to each need.

s

Be sure to represent the role you have been assigned by the instructor. s

After your discussion, present your conclusions and justiﬁcations to the class, and summarize the functions and other aspects of every service you recommend.

1. First Street Fabrics employs 23 administrative personnel in its corporate headquarters. Last year the company purchased personal computers for each of the administrative employees.
Currently, each computer is operated separately, and the computer users share ﬁles and print documents by handing ﬂoppy diskettes back and forth. The staff feels that they can be more effective if a computer network is installed.
2. ABC Chemical Corporation wants to use its LAN to disseminate human resources information, company data, and product information to internal users. In addition, the payroll department wants to automate the process of securing managers’ approval for time cards. 3. Modern Information Services has decided to enter an extremely competitive investment market. To do so, the company must relocate approximately 10 investment traders, 40 administrative staff, and 5 management staff to an ofﬁce in the ﬁnancial district.
The entire company is devoted to maintaining rapid customer service through effective communications. To do so, every employee must be available to clients through a variety of communication channels and must share client data openly with all other company employees. 2-26

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Notes

Written Exercise 2-6:
Designing Network Services

u

Prepare the students to complete the exercise: s a

:15

Tell the students that their responses should include specific services.

Network Services

s

Split up the business scenarios between the previously organized groups. Have the students complete
Exercise 2-6.

u

Allow each group to present its assigned scenario and justify its conclusions.

u

Review answers to
Exercise 2-6.

Answers:
1. The preferred response is file and print services.
2. The preferred response is workflow application services. 3. The preferred response is message services, especially email, integrated email and voice mail, and database services.

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4. Downtown Fast Foods, a local chain of fast food restaurants, needs to centralize their inventory monitoring functions and the process by which individual store managers request shipments of frozen food.
Currently, each manager sends his or her daily sales ﬁgures and weekly food orders via email. The shipping department then sends the frozen food by truck to the individual stores.
The central warehouse must keep a great deal of food in inventory because there is no way to accurately predict weekly sales.

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Network Services

Presentation

Notes

Written Exercise 2-6:
Designing Network Services
(continued)

u

Continue discussing the answers: Answers (continued):
4. The preferred response is application services, and distributed and replicated (for fault tolerance) database services tied directly into the cash registers of each store.

Network Services

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Summary
Computer networks are valuable because of the services that they provide or manage. Among the many possibilities are the following common network services: s File Services. Includes ﬁle transfer, data storage, ﬁle update synchronization, and archiving.

s

Print Services. Provides increased access to printers, eliminates distance constraints, handles simultaneous requests, and shares specialized equipment.

s

Message Services. Facilitates email, integrated email and voice mail, object-oriented applications, workgroup applications, and directory services.

s

Application Services. Allows specialization of servers as well as improved scalability.

s

Database Services. Involves the coordination of distributed data and replication. When an organization implements a computer network, decisions must be made on whether to centralize or distribute network services. Among the many different factors that must be considered are the following: s Control of resources

s

Server specialization

s

Choice of network operating systems

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Network Services

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Notes

Summary

u

Summarize the section.

u

Review the objectives and answer questions.

Objectives:
1. Identify the functions and features of the five basic network services.
2. Determine when network file services should be implemented. 4. Determine when network message services should be implemented.
5. Determine when network application services should be implemented.
6. Determine when and how network database services should be implemented.
7. Identify how the delivery of individual network services is affected by centralized and distributed network architectures.

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Network Services

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Transmission Media
0

SECTION 3

Transmission Media

Duration

02:45

Preparation
Prepare the computer to display animations and/or transparencies.
Organize cable samples for distribution during the appropriate discussion. Transmission Media

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SECTION 3

Transmission Media
In this section, you learn about transmission media, the second basic element of computer networks.

Objectives
Upon completing this section, you should be able to
1. Deﬁne the term transmission media as it relates to computer networks. 2. Identify the appropriate transmission media to meet a stated business need. 3-1

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Transmission Media

Presentation

Notes

Transmission Media

u

Introduce the section.

Objectives

u

Present the section objectives. Transmission Media

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Introducing
Transmission Media
Before a network service can be shared, network computers must have a pathway to contact other computers. Computers use electric currents, radiowaves, microwaves, or light spectrum energy from the electromagnetic (EM) spectrum to transmit signals to each other. (See
Figure 3-1.)
Computers use electronic voltage pulses or electromagnetic waves to send signals.
The physical path through which the electrical voltages and EM waves travel is called transmission media. It is through the transmission media that networked computers signal each other.
Computer networks rely upon the ability of a transmission medium to accommodate a range of electric voltages or EM waves. For many portions of the EM spectrum, a number of transmission media types exist. This section describes the characteristics of some common transmission media.

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Transmission Media

Presentation

Notes

Introducing Transmission
Media

u

Describe signaling as it relates to computer networks. u

Define transmission media.

Transmission Media

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Frequency in Hertz
(Cycles per
1 Second)
3
10
Hertz
30
100
300
1
3
10 Kilohertz
30
100
300
1
3
10 Megahertz
30
100
300
1
3
10 Gigahertz
30
100
300
1
Terahertz
3
10
30
0V
1

Audio Frequency
Power and Telephone

Extremely
Low Frequency (ELF)
Voice Frequency (VF)
Very Low Frequency (VLF)

Radio Waves

Low Frequency (LF)
Medium Frequency (MF)
High Frequency (HF)
Very High Frequency (VHF)
Ultra High Frequency (UHF)
Microwaves

Extremely High
Frequency (EHF)
Submillimeter Waves

0.4mm
0.6
mm

Far Infrared

0.5 mm Visible Spectrum
Intermediate Infrared
Near Infrared

Ultraviolet

Visible Light

Vacuum Ultraviolet

100 kev 1

Soft X-Rays
X-Rays

10
100
Mev
1

0.7mm

Infrared

Near Ultraviolet
10

Response of the Eye

Super High
Frequency (SHF)

Photon
Energy
in
Hertz
Volts (ev)

Hard X-Rays
Soft Gamma Rays

Gamma Rays

Hard Gamma Rays

10

Secondary
Cosmic Rays
(Gamma Rays
Produced by
Cosmic Rays)

100
Gev
1
10

Figure 3-1: Electromagnetic Spectrum

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Transmission Media

Presentation

Notes

Introducing Transmission
Media (continued)

d u 3-1 (Figure 3-1:
Electromagnetic Spectrum)

Briefly introduce the electromagnetic spectrum, referencing recognizable uses of the EM ranges.

Transmission Media

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Common Computer
Network Transmission
Media
Transmission media can be classiﬁed as cable or wireless. Cable media provide a conductor for the electromagnetic signal, while wireless media do not.
You would typically use a single cable media if you are installing a small local area network. You would also use special-purpose cable, or a combination of cable and wireless media, to link more distant stations such as those in a WAN.
Wireless media are essential to networks with mobile computers and are widespread in enterprise and global networks.
Each media type has certain characteristics. You should be aware of their possible beneﬁts and considerations as they relate to the following factors: s

Cost

s

Ease of installation

s

Capacity (bandwidth and throughput)

s

Attenuation

s

Immunity from interference and signal capture

Cost and Ease of Installation
Because absolute cost and ease of installation data are difﬁcult to provide without referring to speciﬁc implementations, you can make relative judgments by comparing each medium to the others.

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Transmission Media

Presentation

Notes

Common Computer Network
Transmission Media u Introduce categories of transmission media (cable and wireless).

u

Emphasize that cable media provide a conductor for the electromagnetic signal, while wireless media do not.

Cost and Ease of Installation

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Transmission Media

u

Explain that cost and ease of installation will not be discussed in detail.

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Capacity
The capacity of a particular transmission medium is often stated as bandwidth. Bandwidth is the range of cycle frequencies, measured in hertz (Hz) or cycles per second, that a transmission medium can physically accommodate.
Bandwidth measurements vary with changes in distance and the signaling techniques used.
You should primarily be interested in throughput, which measures how much binary data can be reliably transmitted within the medium’s usable bandwidth. Throughput is a measurement of the amount of data transmitted within a speciﬁed time period, and is usually measured in bits per second (bps).

Attenuation
Attenuation refers to the tendency of electromagnetic waves to weaken or become distorted during transmission. As a wave passes through a medium, some of its energy is absorbed or scattered by the medium’s physical properties.
While attenuation can be described in very exacting terms, this section makes general performance comparisons. Effective distances, using current techniques, are also provided.

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Transmission Media

Presentation

Notes

Capacity

u

Discuss the difference between bandwidth and throughput, if needed.

Attenuation

u

Discuss attenuation.

Transmission Media

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Interference and Signal
Capture
Finally, transmission media might constrain or guide voltage pulses and electromagnetic waves, but no medium can totally control the entire spectrum. Interference occurs when undesirable electromagnetic waves affect the desired signal. Interference can be caused by many factors, including s Electromagnetic Interference (EMI). EMI is caused by sources such as large electromagnets used in industrial machinery.

s

Radio Frequency Interference (RFI). RFI is caused by transmission sources such as radio stations.

Some emitted electromagnetic waves can be easily intercepted, allowing the transmission to be copied or diverted from its destination. This is called signal capture.
Because data and transmission security is important, you need to know how well the various transmission media resist interference and signal capture. Cable Media
Cable media are wires or ﬁbers that conduct electricity or light. The following examples are covered in this section: s Twisted pair cable

s

Coaxial cable

s

Fiber optic cable

Cable

Signal

Figure 3-2: Cable Media

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Transmission Media

Presentation

Notes

Interference and Signal Capture

u

Discuss interference and signal capture.

Cable Media

d

3-2 (Figure 3-2: Cable Media)

Repeat the definition of cable media.

u

List the cable media that will be discussed. s Coaxial cable

s

Revision 1.0

Twisted pair cable

s

Transmission Media

u

Fiber optic cable

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Twisted Pair Cable

Twisted pair (TP) cable uses copper wire as telecommunication cable.
Because copper is such a good conductor of electrons, copper wires do not constrain electromagnetic signals well.
When two copper wires conduct electric signals in close proximity, a certain amount of electromagnetic interference occurs. This type of interference is called crosstalk.
In addition, because of the electromagnetic range used, TP transmits and receives unwanted signals from other sources. Twisting the copper wires reduces crosstalk and signal emissions. Each intertwined strand conducts a current whose emitted waves are cancelled out by the other wire’s emissions.

Insulation

Copper Wire
Conductor

Figure 3-3: Twisted Pair

Twisted pairs are formed by two insulated 22 to 26 gauge copper wires that are twisted around each other. When one or more twisted pairs are combined within a common jacket, they form a twisted pair cable. The two types of TP cable are s Unshielded

s

Shielded

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Transmission Media

Presentation

Notes

Twisted Pair Cable

d u 3-3 (Figure 3-3: Twisted Pair)

Describe twisted pair cable.

Throughout Section 3, you will be discussing generic transmission media. Avoid protocol or specification details. Do not discuss specifications such as 10BASE-T or IBM
Token-Ring. This section is designed to discuss the transmission media in general terms. Do no present the current specifications for its use.

Transmission Media

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Unshielded Twisted Pair Cable

Unshielded twisted pair (UTP) cable is composed of a set of twisted pairs with a simple plastic encasement.

Plastic
Encasement

Color-Coded
Insulation

Copper Wire
Conductor

Figure 3-4: Unshielded Twisted Pair Cable

UTP is commonly used in telephone systems. It is widely available and has been largely standardized. The Electrical Industries Association
(EIA) popularized a category labeling scheme for ﬁve different qualities of twisted pair cable: s Category 1 and 2–Voice and low-speed data (≤4 Mbps)

s

Category 3–Data (typically 10-16 Mbps, although 100 Mbps is possible) s

Category 4–Data (≤20 Mbps)

s

Category 5–High-speed data (≤100 Mbps)

Category 3 and Category 5 UTP are commonly used in computer networking. Category 3 is suitable for most contemporary computer networks. Category 5 includes some enhancements (such as more twists per foot and a higher grade insulator) to improve the transmission media performance. Category 5 installations also require compatible equipment and more exacting installation techniques.

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Transmission Media

Presentation

Notes

Unshielded Twisted Pair Cable

d

3-4 (Figure 3-4: Unshielded
Twisted Pair Cable)

u

Describe unshielded twisted pair cable.

u

Show a small sample of
UTP.

u

Identify the prescribed uses of the different UTP categories as needed.
Transmission Media

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Drop Cable

Patch Cable

Punch-Down
Block

Wall Jack

Patch panel

Hub
Patch Cable

Figure 3-5: A Common Unshielded Twisted Pair Installation

Computer network UTP is often installed in the same manner as most telephone UTP installations. A user device contains a port which accommodates a modular RJ-45 (4-pair) or RJ-11 (2-pair) telephone connector. These connectors are attached to both ends of a patch cable. One end of the patch cable is inserted into the device’s port and the opposite end is inserted into a wall jack.
The wall jack connects the UTP cable drop (the drop is a length of cable that extends to the user’s location) to one side of a punch-down block.
The opposite side of the punch-down block is wired to a patch panel.
This patch panel provides multiple ports, which use patch cables to connect to other user devices or to the connectivity devices described in
Section 4, “Connectivity Devices.”

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Unshielded Twisted Pair Cable
(continued)

d u 3-5 (Figure 3-5: A Common
Unshielded Twisted Pair
Installation)

Describe how UTP cable is installed. UTP can be installed

As a twisted pair bus with terminators and drop cables (similar to PhoneNet™ used with Apple®
Macintoshes®)

Briefly mention other installation possibilities.

Theoretically, spare voice UTP pairs can be used for computer networks. However, this practice is not recommended by many network installers.
Interference (crosstalk) from the voice wires can be significant. To combine voice and data pairs in the same cable, use a hybrid UTP/STP cable that provides some shielding between the two.

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Transmission Media

Using just long drop cables between the computer and the hub

s

Recommend that voice grade or spare voice pairs not be used.

With other types of punch-down blocks

s

u

Using cross-connects (wiring that spans punch-down block pins) instead of a patch panel

s

u

s

Networking Technologies Instructor Guide (Volume 1)
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0

While RJ-45 connectors are the most commonly used connectors, multipin RS-232 and RS-449 connectors can also be used.
The advantages and disadvantages of UTP are described below: s Cost. The cost of UTP is extremely low compared to other transmission media. It continues to be mass-produced for telecommunications and has become a popular computer network medium. Some network integrators use existing spare wires from telephone cables to signiﬁcantly reduce the already low implementation costs.
However, we do not recommended this practice if the existing UTP cable is lower than Category 3, if the cable drops exceed 100 meters, or if signiﬁcant crosstalk is already present between the voice wires.

s

Ease of Installation. UTP installation equipment is inexpensive, easy to use, and widely available. Installation techniques are so simple that the cable can be adequately installed with very little training. Because voice telecommunication connection techniques have been optimized for easy moves, adds, and changes, UTP is easily managed and reconﬁgured.

s

Capacity. UTP can support data transfer rates from 1 Megabit per second (Mbps) to 1 Gigabit per second (Gbps) at distances up to
100m. Ten Mbps and 100 Mbps are the most common transmission rates in use today.

s

Attenuation. All copper wire suffers from rapid attenuation when used as a communications medium. Current technology restricts the effective range of UTP to hundreds of meters.

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Unshielded Twisted Pair Cable
(continued)

u

Discuss the cost characteristics. u

Discuss the ease-of-installation characteristics.

u

Discuss the capacity characteristics. u

Discuss the attenuation characteristics. Transmission Media

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s

Immunity from interference and signal capture. The copper cable used in UTP is very susceptible to interference. Although the twists greatly reduce crosstalk, a certain amount of interference exists between pairs of wires.
Also, signals on the pairs are easily inﬂuenced by outside emitters of electromagnetic waves (like electric motors). External devices can also be used to intercept signals that are emitted from the pairs, breaching the security of a network.
Beneﬁts

Considerations

Relatively inexpensive.

Relatively high rate of attenuation. Easily installed, managed, and reconﬁgured. Current technology restricts the effective range of UTP to hundreds of meters.

Basic technology and standards are mature and stable. Susceptible to interference and signal capture.

Table 3-1: Unshielded Twisted Pair (UTP) Beneﬁts and Considerations

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Unshielded Twisted Pair Cable
(continued)

u

Discuss the medium’s resistance to interference and signal capture.

u

Review the UTP benefits and considerations table.

Transmission Media

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Shielded Twisted Pair Cable
Today, most TP cable is unshielded, but some forms of shielded twisted pair (STP) still exist.
Plastic
Encasement

Shielding

Color-Coded
Insulation

Copper
Conductor

Figure 3-6: Shielded Twisted Pair

STP is insulated cable that includes bundled pairs wrapped in a foil shielding. Various transmission media speciﬁcations from Apple®
Computer and IBM® use STP cable.
For example, IBM employs a type speciﬁcation for different qualities and conﬁgurations of STP. Networks conforming to each vendor’s speciﬁcations have their own unique installation requirements, including connectors and length restrictions.

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Shielded Twisted Pair Cable

d

3-6 (Figure 3-6: Shielded
Twisted Pair)

u

Describe shielded twisted pair cable.

u

Show a small sample of
STP.

Transmission Media

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IBM Data Connector
(Token Ring)

Shielded Twisted
Pair Cable

Shielded Twisted
Pair Cable

Apple LocalTalk
Connector

Figure 3-7: Common Shielded Twisted Pair Cables

The advantages and disadvantages of STP cable are described below: s Cost. Bulk STP is moderately expensive. It currently costs more than UTP but is less expensive than thick coaxial or ﬁber optic cable.

s

Ease of Installation. Unlike UTP, both STP and coaxial cable require an electric ground, which makes the manufacture of cables more complex.
However, the connectors used in common STP implementations are more complex than those used in coaxial cable implementations.
If you use standardized and preconﬁgured cables, there is little difference between UTP, STP, and coaxial cable in ease of installation. 3-13

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Shielded Twisted Pair Cable
(continued)

d

3-7 (Figure 3-7: Common
Shielded Twisted Pair Cables)

u

Describe the STP cables shown in Figure 3-7.

u

Discuss the cost characteristics. u

Discuss the ease of installation characteristics.
Transmission Media

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s

Capacity. Theoretically, with the reduction of outside interference,
STP can use higher frequencies and more bandwidth-efﬁcient signaling techniques.
It is capable of greater transmission speeds (up to 500 Mbps at
100m), but it has not been widely implemented at data rates higher than 155 Mbps. The most common transmission rate in use today is
16 Mbps.

s

Attenuation. STP suffers from attenuation at a rate similar to UTP.
Current technology restricts the effective range of STP to hundreds of meters.

s

Immunity from interference and signal capture. The biggest difference between UTP and STP is the reduction of interference and EMI emissions provided by STP’s shielding. However, STP still suffers from relatively low immunity from interference.
Beneﬁts

Considerations

Technology and standards are fairly mature and stable.

More expensive and harder to install (when connectors are not preinstalled) than UTP and coaxial cable.

Higher bandwidth available.

Relatively high rate of attenuation (similar to UTP).
Susceptible to interference and signal capture, although less so than UTP.

Table 3-2: Shielded Twisted Pair (STP) Beneﬁts and Considerations

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Shielded Twisted Pair Cable
(continued)

u

Discuss the capacity characteristics. u

Discuss the attenuation characteristics. u

Discuss the medium’s resistance to interference and signal capture.

u

Review the STP benefits and considerations table.
Transmission Media

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Coaxial Cable

Coaxial cable (commonly called “coax”) is made of two conductors that share a common axis, hence the name (“co,” “axis”). Typically, the center of the cable is a relatively stiff solid copper wire or stranded wire encased in insulating plastic foam.
The foam is surrounded by the second conductor, a wire mesh tube
(some include conductive foil wrap), which serves as a shield from interference and signal capture.
A tough, insulating plastic tube forms the cover of the cable.
Plastic
Encasement

Outer
Conductor

Insulation

Inner
Conductor

Figure 3-8: Coaxial Cable

Several coaxial cable standards are used in computer networking. The most common types meet one of the following ohm and size standards
(ohms are a measurement of the cable’s resistance to direct or alternating electric currents): s 50 ohm RG-8 and RG-11 (used in thick Ethernet speciﬁcations discussed later)

s

50 ohm RG-58 (used in thin Ethernet speciﬁcations described later)

s

75 ohm RG-59 (used for cable TV)

s

93 ohm RG-62 (used for ARCnet speciﬁcations)

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Coaxial Cable

d

3-8 (Figure 3-8: Coaxial
Cable)

u

Describe coaxial cable.

u

Show a small sample of solid core and/or stranded core coaxial cable.

u

Describe the prescribed uses of the different types of coax as needed.
Transmission Media

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Coaxial
Cable
Terminator

Tap

T-Connector

Figure 3-9: Common Coaxial Cable Installation

Coaxial cable is most often installed between devices. At each user location a connector is attached to provide a user interface.
The interface can be attached by cutting the cable and installing a
T-connector to both ends or by applying special clamp-like devices called taps.
Taps are mechanical devices that use conducting teeth to penetrate the insulation and attach directly to the wire conductor.
To maintain the correct electrical properties of the wire, you must ground and terminate the cable. An electrical ground completes the required electrical circuit, while a terminator dampens signal reﬂections (wave reﬂection will be discussed later).

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Coaxial Cable (continued)

d u 3-9 (Figure 3-9: Common
Coaxial Cable Installation)

Describe how coaxial cable is installed.

Transmission Media

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The advantages and disadvantages of coaxial cable are described below: s

Cost. The cost of coaxial cable increases with the diameter and composition of the conductors.
The cost of thin coaxial cable is relatively low (less than STP or
Category 5 UTP). Thick coaxial cable is moderately expensive (more than STP or Category 5 UTP).
Both are more expensive than Category 3 UTP (all comparisons are made in reference to bulk cable with no connectors).

s

Ease of Installation. The initial installation of coaxial cable is relatively simple. However, current installation techniques usually use a single strand of cable, which can be difﬁcult to manage and reconﬁgure. Local drops can be connected to the base cable to make device connections easier.

s

Capacity. Using current technologies, coax supports data transfer rates between twisted pair and ﬁber optic cable, although the typical data rate in use today is 10 Mbps.
Much greater data rates are available. However, these higher rates are only infrequently used in computer networking. Coaxial cable’s bandwidth potential increases with the diameter of the inner conductor. s

Attenuation. As a copper wire media, coaxial cable suffers from high attenuation, but at a much lower rate than either variety of twisted pair. Using current LAN technology, the effective range of coaxial cable is in the low thousands of meters.

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Coaxial Cable (continued)

u

Discuss the cost characteristics. u

Discuss the ease of installation characteristics.

u

Discuss the capacity characteristics. u

Discuss the attenuation characteristics. Transmission Media

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s

Immunity from interference and signal capture. While copper wire generally is a poor resistor to interference, the shielding used in coaxial cable provides some protection.
Beneﬁts

Considerations

Relatively simple to install.

More expensive than Category
3 UTP.

Supports higher bandwidths than TP although not commonly used in LANs at rates faster than 10 Mbps.

Some installation techniques make coaxial cable hard to manage and reconﬁgure.

Resists interference better than twisted pair.

Moderately high attenuation
(less than TP).

Relatively sturdy.

Moderately susceptible to interference (under extreme conditions). Table 3-3: Coaxial Cable Beneﬁts and Considerations

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Notes

Coaxial Cable (continued)

u

Discuss the medium’s resistance to interference and signal capture.

u

Review the coaxial cable benefits and considerations table. Transmission Media

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Fiber Optic Cable

Fiber optic cable is made of a light-conducting glass or plastic core surrounded by more glass, called cladding, and a tough outer sheath.
The center core provides the light path or waveguide while the cladding is composed of varying layers of reﬂective glass. The glass cladding is designed to refract light back into the core. Each core and cladding strand is surrounded by a tight or loose sheath.
In tight conﬁgurations, the strand is completely surrounded by the outer plastic sheath. Loose conﬁgurations use a liquid gel or other material between the strand and the protective sheath.
In both cases, the sheath provides the necessary cable strength to protect the ﬁber from excessive temperature changes, bending, stretching, or breaking.
Plastic
Encasement

Glass or Plastic
Fiber

Loose
Configuration
Liquid Gel
Tight
Configuration

Plastic
Encasement

Strength
Wires

Plastic
Sheath

Glass or Plastic
Fiber

Figure 3-10: Fiber Optic Cable

Fiber optic cables can be composed of a single jacketed strand, but often multiple strands are bundled together in the center of a cable.
Some ﬁber optic cables will also provide an additional metallic, kevlar™, or ﬁberglass wire to increase cable strength, but this is not required.

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Notes

Fiber Optic Cable

d u 3-10 (Figure 3-10: Fiber Optic
Cable)

Describe fiber optic cable.

Transmission Media

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Optical ﬁbers are much smaller and more lightweight than copper wires.
Therefore, large ﬁber optic cables can carry more conductors than similarly sized copper cables, which makes them ideal for limited space environments. Optical ﬁbers can be multimode or single mode in nature. Single-mode ﬁber has been optimized to allow only one light path; multimode ﬁber allows various light paths.
The physical characteristics of the multimode ﬁber’s layers control the speed of the various modes. By bending the light at different rates, the signal’s parts arrive simultaneously and appear to be a single pulse to the receiver.
Single-mode ﬁber has a higher capacity but costs more to produce and use than multimode ﬁber.
Cladding

Core

Single-Mode

Multimode
Figure 3-11: Single-Mode and Multimode Propagation

The types of ﬁber optic cable are differentiated by mode, composition
(glass or plastic), and core/cladding size. The size and purity of the core determines the amount of light that can be transmitted.

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Fiber Optic Cable (continued)

u

d u Show a small sample of fiber optic cable.

3-11 (Figure 3-11:
Single-Mode and Multimode
Propagation)

Explain that fiber optic cable can be single-mode or multimode. The mode often dictates the type of interface used.
Single-mode fibers are most often used with laser optics that can provide purer light. Multimode fibers are used with the cheaper LED light sources.
This difference can affect cost, ease of installation, capacity, and attenuation.

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Transmission Media

Laser devices are more expensive, harder to install, provide much greater capacity, and their signals attenuate less rapidly.

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Common types of ﬁber optic cables include s 8.3 micron core/125 micron cladding single-mode

s

62.5 micron core/125 micron cladding multimode

s

50 micron core/125 micron cladding multimode

s

100 micron core/140 micron cladding multimode

A common LAN installation of ﬁber optic cable starts at a user device that contains two optical interfaces (incoming and outgoing). The interface is connected directly to ﬁber optic cables, which have been terminated with biconic or other mechanical connectors.
Connection
(Splice) Center

Hub
(Connectivity Device)

Mechanical
Splice (Using ST
Connectors)

Figure 3-12: A Common Fiber Optic Cable Installation

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Fiber Optic Cable (continued)

u

List the common types of fiber optic cable.

u

Describe a common fiber optic cable installation.

d

3-12 (Figure 3-12: A Common
Fiber Optic Cable Installation)

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Multiple lengths of ﬁber optic cable, when necessary, are spliced together using electric fusion, a chemical epoxy process, or mechanical connectors. The opposite ends of the cables are attached to a connection (splice) center or one of the connectivity devices discussed later in this course.
Optical interface devices convert computer signals and light pulses to and from the optical ﬁbers. The light pulses are generated by light emitting diodes (LEDs) on multimode ﬁber or injection laser diodes
(ILDs) on single-mode ﬁber. They are reconverted to electric signals by
P intrinsic N diodes or avalanche photodiodes. s Cost. Historically, bulk fiber and connectors have been relatively expensive compared to copper wire, but these costs are falling rapidly. However, the extreme cost of installation far exceeds the cost of materials.

s

Ease Of Installation. The nature of fiber optic cable poses installation problems. Every ﬁber junction, splice, or connection must be made with extreme care to ensure that the light path is unobstructed. Installers must also be careful not to excessively stretch or bend the ﬁber.

s

Capacity. Optical fibers support extremely high bandwidths because they are limited by the high-frequency photon properties of light rather than by lower-frequency properties of electrical systems.
Current technologies allow data rates from 100 Mbps to over 2 Gbps
(at distances from 2 to 25 km).
The data rate of a given ﬁber optic system is dependent upon the ﬁber composition (glass or plastic), the mode, and the wavelength
(and therefore the frequency) of the light transmitted.

s

Attenuation. Fiber optic cables have extremely low attenuation rates. The amount of attenuation varies depending upon the operating wavelength, but effective ranges are usually measured in kilometers. Therefore, ﬁber optic cable attenuates much less than any copper wire transmission medium.

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Fiber Optic Cable (continued)

u

Discuss the cost characteristics. u

Discuss the ease of installation characteristics.

u

Discuss the capacity characteristics. u

Discuss the attenuation characteristics. Transmission Media

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s

Immunity from interference and signal capture. Due to the use of the light spectrum, ﬁber optic cables do not leak signals and are immune to electromagnetic interference and eavesdropping.
Beneﬁts

Considerations

Supports very high bandwidths–depending upon the mode and distance–from
100 Mbps to >2 Gbps.

Relatively expensive cable and hardware. Low attenuation rates possible
(measured in kilometers).

Connections require high-precision manufacturing and complex installation.

Immune to interference or eavesdropping from outside the cable. Relatively complex to conﬁgure and install.

Table 3-4: Fiber Optic Cable Beneﬁts and Considerations

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Presentation

Notes

Fiber Optic Cable (continued)

u

Discuss the medium’s resistance to interference and signal capture.

u

Review the fiber optic cable benefits and considerations table. Transmission Media

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Written Exercise 3-1:
Implementing Cable
Media
In this exercise, you and your group select the transmission media or combination of media that is most appropriate for the following business scenarios. During your group discussions, play the role you were assigned by the instructor. Be prepared to defend the solution offered by your group.
1. First Street Fabrics currently houses 23 administrative personnel in an old 4,000 square foot ofﬁce that has been used for over 50 years with very few improvements.
Last year the company purchased personal computers for each of the administrative employees. Currently, each computer is operated separately, and the computer users share ﬁles and print documents by handing ﬂoppy diskettes back and forth.
The staff feels that they can be more effective if a computer network is installed. The president has agreed to fund a pilot computer networking project, but is not convinced that it can be cost effective.
The cable system must be easily re-conﬁgured due to a large number of ongoing moves, add items, and changes.
2. ABC Chemical Corporation is committed to automating a large manufacturing facility. The facility currently houses thousands of highly technical workers, volatile chemicals, and complex equipment.
Management would like to link all administrative ofﬁces to computer-operated manufacturing stations.
A primary management goal is to install a cable system that will provide a minimum of 100Mb/sec bandwidth while completely eliminating the possibility of data “eavesdropping” by unsavory competitors. 3-24

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Written Exercise 3-1:
Implementing Cable Media

u

a

:30

u

Introduce the exercise.

Have the students complete
Exercise 3-1.

Remind the student to discuss the following: s Cost

s

Reconfiguration

s

Capacity

s

u

Transmission Media

s

Immunity from interference Data security

Review the answers to
Exercise 3-1.

Preferred answers:
1. UTP is the most appropriate cable transmission media solution for this business scenario. r r

Probably does not exceed 300 feet (or 100 meters) in any direction. Older building probably does not use Category 3 or higher UTP.

r

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Low number of stations implies low capacity needs. Tendency to reorganize the office space makes ease of reconfiguration a consideration.

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3. Modern Information Services has decided to enter an extremely competitive investment market. To do so, the company must relocate approximately 10 investment traders, 40 administrative staff, and 5 management staff to an ofﬁce in the ﬁnancial district.
This new venture is constrained by tight budgets, but the Vice
President of Operations is very involved in the facility planning. He has organized the ofﬁce space into small workgroup areas.
He is also intrigued with sophisticated technical equipment and has already ordered 8 pair of Category 5 UTP cable, high-output ﬂuorescent lights, and modular walls for each worksite.
He now seeks help in implementing and maintaining the computer network. 4. Downtown Fast Foods has decided to centralize its inventory monitoring functions and the process by which store managers request shipments of frozen food.
The stores, located within 50 miles of each other, need to be networked so that every sale is recorded in the local inventory database. The facilities are newly constructed, with no interference problems at all. Cost is an important consideration.

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Written Exercise 3-1:
Implementing Cable Media
(continued)

u

Continue reviewing the answers .

2. Fiber optic cable is the most appropriate cable solution for this business scenario. r High capacity is required.

r

A large manufacturing facility probably exceeds hundreds of meters in some direction.

r

Volatile chemicals and processes can be sensitive to electric shock and static.

r

The concerns regarding eavesdropping eliminate the use of copper cabling.

3. STP and fiber optic (on stations sensitive to eavesdropping) are the most appropriate solution.
Existing Category 5 UTP should be tested for suitability and replaced if necessary.
Fluorescent lights are EMI emitters.

r

Information used by the traders is sensitive.
Eavesdropping would be a concern.

r

Modular walls imply a tendency to move offices and equipment.

4. UTP is the most appropriate transmission media solution for this business scenario. r r

Revision 1.0

No problems would exist with interference.
Cost is important.

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Cable Transmission Media
Comparison
Table 3-5 summarizes the material in the previous pages. Costs are relative and are presented for comparison purposes only.
Media

Cost

Ease of
Installation

Capacity
Range

Attenuation

Immunity from
Interference
and Signal
Capture

Unshielded twisted pair

Extremely low

Very simple

1 to 100 Mbps
(multiple
wires);
10 Mbps is most common

High; maximum effective range in 100s of meters Low

Shielded twisted pair

Moderate

Simple to moderate 1 to 155 Mbps
(multiple
wires);
16 Mbps is most common

High; maximum effective range in 100s of meters Moderately low

Coaxial cable

Low to moderate Simple

Varies by size and composition between 1 Mbps and more than
1 Gbps; 10
Mbps is most common Moderate; maximum effective range in low kilometers Moderate

Fiber optic cable Moderate to high Difﬁcult

10 Mbps to more than
2 Gbps;
100 Mbps is most common

Low; maximum High effective range in 10s of kilometers Table 3-5: Cable Transmission Media Comparison

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Transmission Media

Presentation

Notes

Cable Transmission Media
Comparison

u

Introduce the table.

Transmission Media

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Wireless Media
Wireless media transmit and receive electromagnetic signals without an electrical or optical conductor. Technically, the earth’s atmosphere provides the physical data path for most wireless transmissions.
However, because various forms of electromagnetic waves are used to carry signals, the EM waves are often referred to as media. The following wireless media are discussed in this subsection: s Radiowave

s

Microwave

s

Infrared light

The LAN and WAN implementations of each medium differ slightly.
Because their characteristics are similar, they are discussed together.

Radio Frequency
The portion of the electromagnetic spectrum which is usually considered radio frequency (RF) resides between 10 KHz and 1 GHz. This range of radio frequencies includes broadcast bands commonly called s s

Very high frequency (VHF) television and FM radio

s

x

Shortwave radio

Ultra-high frequency (UHF) radio and television

A band is a contiguous group of frequencies which, because of convenience or technical details, are used for a single purpose (or treated like a single frequency).

Radio frequencies have been divided between regulated and unregulated bandwidths.

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Transmission Media

Presentation

Notes

Wireless Media

u

Repeat the definition of wireless media.

u

List the wireless media that will be discussed.

Radio Frequency

Describe Radio Frequency
(RF).

u

Define the term band as needed. Revision 1.0

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Users of regulated frequencies must get a license from the regulatory bodies who have jurisdiction over the desired operating area (the FCC in the United States, the CDC in Canada, and so on).
The licensing process can be difﬁcult, but licensed frequencies guarantee clear transmissions within a speciﬁc area.
The drawbacks of this process include relatively long implementation delays, increased cost, and lack of ﬂexibility in moving equipment to new locations. Frequency in Hertz
(Cycles per
Second)
Very Low Frequency (VLF)

10
30 Kilohertz
100
300
1
3
10 Megahertz
30
100
300
1
3
10 Gigahertz
30
100
300

Radio Waves
Low Frequency (LF)
Medium Frequency (MF)
High Frequency (HF)
Very High Frequency (VHF)
Ultra High Frequency (UHF)
Microwaves

Super High
Frequency (SHF)
Extremely High
Frequency (EHF)
Submillimeter Waves

Figure 3-13: Radio Frequencies

Error-free transmissions are impossible to guarantee in uncontrolled frequency bands. However, the equipment used in unregulated bands must operate at regulated power levels (under one watt in the U.S.) to minimize interference with other signals.
The lower the device power, the smaller its effective area. Multiuser interference is limited to a relatively small area.
Radio frequency waves can be broadcast omnidirectionally, or ﬁne tuned for directional emissions from a variety of transmitting antennas. The type of antenna and transceiver determine the frequency and power of the RF signal.

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Transmission Media

Presentation

Notes

Radio Frequency (continued)

u

d

Use the commercial radio example as needed.

Commercial radio stations often refer to the band of frequencies they are using as a single frequency.
However, typical radio transmissions actually cover a range of frequencies and wavelengths.
Because most tuning equipment is designed to address the entire bandwidth at the kilohertz or megahertz level, the distinction between one frequency and a band is overlooked. 3-13 (Figure 3-13: Radio
Frequencies)

Discuss the capacities and frequencies of radio transmission. u

Describe radio frequency transmissions. Revision 1.0

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Global systems use shortwave, which propagates beyond the horizon, and local systems use nearly line-of-sight VHF or UHF. Each of the designated ranges has characteristics that affect their use in computer networks. Attenuation
Attenuation found in wireless media transmissions takes on different characteristics than the attenuation experienced on cable media.
Attenuation pertaining to RF transmissions is described as a transmission loss of a radio circuit consisting of a transmitting antenna, a receiving antenna, and the intervening propagation medium. Attenuation is usually expressed in decibels.
Attenuation of all RF ranges are dependent upon the frequency and power of the signal (the higher the frequency and power level, the less rapidly the signal attenuates).
Transmission through the clear atmosphere is subject to attenuation by molecular oxygen and water vapor. This is referred to as atmospheric attenuation. Included in this category is attenuation introduced due to rain and snow, clouds and fog, and (at some frequencies) by electrons in the ionosphere.
Rain has the most signiﬁcant effect on wireless transmissions, and can cause attenuation in frequencies below 10 GHz. However, it is of more importance in frequencies above 10 GHz.
Attenuation due to rain depends on both the liquid-water content
(drop-size) and the velocity of the fall of the drops. At frequencies above
40 GHz, the speciﬁc attenuation depends primarily on the concentration of small drops.
For most drop sizes, the attenuation rate does not increase appreciably for frequencies above 100 GHz. Calculating attenuation also requires allowances for the effective path length through the rain.
Very small water droplets suspended as clouds or fog can also cause serious attenuation. Transmissions below 2 GHz are affected more seriously by heavy clouds than by heavy rainfall.

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Transmission Media

Presentation

Notes

Attenuation

u

Emphasize the main causes of attenuation on wireless media. A complete discussion of attenuation is beyond the scope of this course. Discuss the main atmospheric issues. Transmission Media

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Types of Radio Transmission
This section examines three classes of RF transmissions: s Low-power, single-frequency

s

High-power, single-frequency

s

Spread spectrum

Low-Power, Single-Frequency Radio
Single-frequency transceivers operate at only one frequency. Low-power devices are often used in short-distance, open environments. Although the relatively long waves of low frequencies can pass through some materials, their low power restricts them to short or unobstructed paths.
Low frequencies and power levels do not sustain very high transmission rates. Typical rates start at less than 1 Mbps.
Single-frequency systems might offer transmission speeds that approach the speed of copper-wired networks, but they are costly and transmission distance remains limited. s Frequency Range. Low-power, single-frequency systems can operate within the entire RF range. Computer networks typically use the higher GHz ranges because they offer higher transmission rates.

s

Cost. Depending on the combination of transceiver and antenna used, low-power, single-frequency systems are moderately priced compared to other wireless media.

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Transmission Media

Presentation

Notes

Types of Radio Transmission

u

List the classes of RF transmissions that will be discussed: s

s

s

u

Low-power, single-frequency High-power, single-frequency Spread spectrum

Qualify the terms low-power, high-power, and single-frequency as needed.

Low-Power, Single-Frequency
Radio

u

Describe low-power, single-frequency radio.

u

Provide a common example. u

Discuss the frequency range characteristics.

u

Discuss the cost characteristics. Revision 1.0

Use a garage door opener or some other hand-held low-power and single-frequency radio remote control as an example.

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Transmission Media

The terms low-power, high-power, and single-frequency were created for use in this class. Similar terms have not been standardized by the industry. However, using the definitions provided, most transmissions and devices can be categorized as one or the other. Spread spectrum is an industry term.

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s

Ease of Installation. Ease of installation depends on the combination of transceiver and antenna used. Most systems are easily installed with preconﬁgured antenna and other equipment.
Others require installation and tuning by skilled technicians.

s

Capacity. Transmission rates start at less than 1 Mbps and approach 10 Mbps.

s

Attenuation. Because these devices operate at very low poser levels, effects of attenuation are relatively high.

s

Immunity from interference and signal capture. Single-frequency signals have extremely low immunity from interference. They are also extremely vulnerable to signal capture when the signal power is high enough to extend the signal beyond exterior walls.
Most low-power LAN devices operate with signal strengths of less than 1 watt. The weak waves they produce do not typically pass through solid objects or extend for more than a few tens of meters; eavesdropping must occur in their immediate area.

Table 3-6 shows the low-power, single-frequency beneﬁts and considerations. Beneﬁts

Considerations

Moderately priced (increases with higher data rates).

May require frequency licensing and approved equipment.

Relatively simple installation.

Only low bandwidths are possible
(1 to 10 Mbps).

Signals are partially or fully constrained to intended area by walls and other objects.

Highly susceptible to interference.

Stations can be stationary or mobile. Susceptible to signal capture.

Table 3-6: Low-Power, Single-Frequency RF Beneﬁts and Considerations

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Transmission Media

Presentation

Notes

Low-Power, Single-Frequency
Radio (continued)

Discuss the ease-of-installation characteristics.

u

Discuss the capacity characteristics. u

Discuss the attenuation characteristics. u

Discuss the medium’s resistance to interference and signal capture.

u

Review the low-power, single-frequency benefits and considerations table.

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High-Power, Single-Frequency Radio
High-power devices can cover long distances and pas through dense materials. These devices are often used in long-distance outdoor environments. Some frequencies operate on unobstructed line-of-sight paths; other frequencies can be bounced off the earth’s atmosphere.
The ﬂexibility of the signal path makes high-power, single-frequency systems ideal for mobile transmissions. High-power, single-frequency systems offer data rates similar to their low-power counterparts, but at much longer distances and at a much higher cost. s Frequency Range. High-power, single-frequency systems can operate within the entire RF range. Computer networks typically use the higher GHz ranges because they offer higher data rates.

s

Cost. Although radio transceivers are relatively inexpensive, expensive antenna towers, repeaters, or high-output transceivers can make high-power, single-frequency systems moderately expensive. s

Ease of Installation. High-power system installations are complex.
They often involve dangerously high voltages and require precise tuning by skilled technicians.

s

Capacity. Transmission rates start at less than 1 Mbps and approach 10 Mbps.

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Transmission Media

Presentation

Notes

High-Power Single-Frequency
Radio

Describe high-power, single-frequency radio.

u

Provide a common example. u

Discuss the frequency range characteristics.

u

Discuss the cost characteristics. u

Discuss the ease-of-installation characteristics.

u

Discuss the capacity characteristics. Revision 1.0

Use amateur radio (HAM) as an example.

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s

Attenuation. The high power levels sustain the signal and resist attenuation much better than low-power devices. Because these devices operate at very high power levels, effects of attenuation are relatively low.

s

Immunity from interference and signal capture. Single-frequency signals have extremely low immunity from interference.
High-power signals are just as vulnerable to eavesdropping as low-power signals, but because high-power signals span a much larger area, the signals can be intercepted much more easily.

Table 3-7 shows the high-power, single-frequency beneﬁts and considerations. Beneﬁts

Considerations

Relatively low attenuation.

May require frequency licensing and approved equipment.

Signals can reach long distances.

Moderately expensive.

Accessible to users throughout the world.

Must be installed carefully with complex tuning equipment.

Stations can be stationary or mobile, even on aircraft or marine vessels. Only low bandwidths are possible
(1 to 10 Mbps).
Highly susceptible to interference.
Susceptible to signal capture.

Table 3-7: High-Power, Single-Frequency RF Beneﬁts and Considerations

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Transmission Media

Presentation

Notes

High-Power, Single-Frequency
Radio (continued)

u

Discuss the attenuation characteristics. u

Discuss the medium’s resistance to interference and signal capture.

u

Review the high-power, single-frequency benefits and considerations table.

Transmission Media

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Spread Spectrum Radio
Although spread spectrum relies upon similar frequencies as other RF transmissions, it uses multiple frequencies simultaneously. The following are two common spread spectrum modulation schemes: s Direct sequence modulation

s

Frequency hopping

Direct sequence modulation spreads encoded data, called chips, across a subset of radio frequencies. In addition to the required data, the chips can include spurious signals.
The intended receiver knows which speciﬁc frequencies are valid and deciphers the signal by collecting valid signals and ignoring the spurious signals. The valid signals are then used to reassemble the data.
Because multiple subsets can be used within any frequency range, direct sequence signals can coexist with other signals. Unwanted signals are simply ignored or treated as a spurious signal or noise.
0

0
1

1
1

1

0
1

1

1
0

0

1

0 1 1 0 1 1 1 1 0 0 0 1 1
Figure 3-14: Direct Sequence Spread Spectrum

Although direct sequence signals can be intercepted almost as easily as other RF signals, eavesdropping is ineffective because it is quite difﬁcult to determine which speciﬁc frequencies to monitor, retrieve all the chips, identify valid data, and interpret the signal.

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Transmission Media

Presentation

Notes

Spread Spectrum Radio

u

d e u

Describe spread spectrum radio. 3-14 (Figure 3-14: Direct
Sequence Spread Spectrum)

Run the Direct Sequence
Spread Spectrum animation. Describe direct sequence modulation. Transmission Media

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0
0

0 0 1 0

1
1 1 1 0
1 1 0 1

0 1 1 0 1 1 1 1 0 0 0 1 1
Figure 3-15: Frequency Hopping Spread Spectrum

Frequency hopping quickly switches between predetermined frequencies. Both the transmitter and receiver must follow the same pattern and maintain complex timing intervals.
Additional bandwidth is available by simultaneously hopping between multiple bands, whereby all the frequencies in the band may be used for transmitting data. s Frequency Range. Spread spectrum systems can use the entire
RF range; however, they typically operate in unlicensed ranges.

s

Cost. Depending on the combination of transceiver and antenna used, spread spectrum systems are moderately priced compared to other wireless media.

s

Ease of Installation. Most spread spectrum systems are purchased as a preconﬁgured set of devices and antenna. Depending on the complexity of this equipment, installation ranges from simple to moderately complex.

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Transmission Media

Presentation

Notes

Spread Spectrum Radio (continued)

d e 3-15 (Figure 3-15: Frequency
Hopping Spread Spectrum)

Run the Frequency Hopping
Spread Spectrum animation. Describe frequency hopping. u

Provide a common example. u

Discuss the frequency range characteristics.

u

Discuss the cost characteristics. u

Discuss the ease-of-installation characteristics.

Revision 1.0

Use military equipment as an example.

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s

Capacity. Typical transmission rates range from 2 to 6 Mbps.
However, use of gigahertz frequencies and wider ranges will lead to a rapid increase in transmission rates.

s

Attenuation. Because these devices normally operate at very low power, they usually suffer from relatively high attenuation.

s

Immunity from interference and signal capture. As with all RF radio, the EM waves used by spread spectrum resist interference fairly poorly. However, spread spectrum resists signal capture.
Potential eavesdroppers must know which group of frequencies to access. The sequences are kept secret, and added security can be attained by introducing “dummy” signals to confuse eavesdroppers.

Table 3-8 shows spread spectrum beneﬁts and considerations.
Beneﬁts

Considerations

Easily installable preconﬁgured systems available.

May require frequency licensing and approved equipment.

Bandwidth is restricted only by frequency availability.

Moderately expensive.

High immunity from signal capture. Relatively high attenuation from typical low-power devices.

Stations can be stationary or mobile. Somewhat susceptible to interference. Table 3-8: Spread Spectrum RF Beneﬁts and Considerations

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Transmission Media

Presentation

Notes

Spread Spectrum Radio (continued)

u

Discuss the capacity characteristics. u

Discuss the attenuation characteristics. u

Discuss the medium’s resistance to interference and signal capture.

u

Review the spread spectrum benefits and considerations table.
Transmission Media

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Microwave
Microwave data communication systems exist in two forms: s Terrestrial (earth-based) systems

s

Satellite systems

Functionally, they each use the same frequencies and are similar, but the capabilities of each are somewhat different.
Frequency
in Hertz
(Cycles per
Second)
Ultra High Frequency (UHF)

1
3
10 Gigahertz
30
100
300

Microwaves

Super High
Frequency (SHF)
Extremely High
Frequency (EHF)
Submillimeter Waves

Figure 3-16: Microwave Frequencies

Terrestrial Microwave

Terrestrial microwave typically uses directional parabolic antennas that require an unobstructed path or line-of-sight to other units. Terrestrial microwave signals, commonly in the low GHz frequency range, are generated by a transceiver.
Microwave links are often used to link separate buildings where cable installation would be troublesome or more expensive. However, because terrestrial microwave equipment often uses licensed frequencies, additional cost and time constraints are imposed by the licensing organization or government.
Smaller scale terrestrial microwave can also be used within buildings.
These microwave LANs typically use small transmitters that communicate with centrally placed omnidirectional hubs. (Hubs are simple connection devices that are explained in another section.)
Multiple hubs can then be interconnected to create a complete network.

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Transmission Media

Presentation

Notes

Microwave

d u 3-16 (Figure 3-16: Microwave
Frequencies)

List the classes of microwave systems that will be discussed: s s

Terrestrial (earth-based) systems Satellite systems

Terrestrial Microwave

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Describe terrestrial microwave. This document should only be used by a Novell-certified instructor.
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s

Frequency Range. Terrestrial microwave systems usually operate in the low GHz range (typically between 4 to 6 and 21 to 23 GHz).

s

Cost. Equipment costs depend on the operating signal strength and frequency. Short-distance systems, used at hundreds of meters, are relatively inexpensive; long-distance systems, used at kilometer distances, can be quite expensive.
Terrestrial microwave systems can be leased from service providers to reduce the initial ﬁxed costs. Short-distance microwave systems can also reduce costs by using higher frequency transmissions that work with smaller, cheaper antennas.

s

Ease of Installation. Line-of-sight systems are difficult to install because they require very exacting adjustments, often made by trial and error, to ensure proper alignment.
Access to suitable transceiver locations can be a problem when an organization does not have a clear line-of-sight between two stations. In this situation, property easements or other arrangements must be made.
In addition, because terrestrial microwaves typically operate in licensed frequencies, installations require expensive and time-consuming licensing procedures.

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Transmission Media

Presentation

Notes

Terrestrial Microwave (continued)

u

Discuss the frequency range characteristics.

u

Discuss the cost characteristics. u

Discuss the ease-ofinstallation characteristics.

Transmission Media

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s

Capacity. While maximum capacity depends on frequency, typical data rates for a single-frequency range from

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