Local Area Networks (LANs)

Local Area Networks

(LANs):

Academic Student Guide

Published by ComputerPREP



, Inc.

Phoenix, Arizona

ACL03-CNLANS-PR-205

Version 6.0P

Local Area Networks (LANs)

Developers

Meagan McLaughlin and Brent Capriotti

Editors

Jill McKenna and David Oberman

Publishers

LeAnna Shank and Tina Strong

Project Manager

Karlene Copeland

TRADEMARKS

ComputerPREP  is a registered trademark of ComputerPREP, Inc. in the United States and other countries.

Microsoft, Microsoft Internet Explorer logo, and Windows are either registered trademarks or trademarks of the Microsoft Corporation in the United States and/or other countries. All other product names and services identified throughout this book are trademarks or registered trademarks of their respective companies. They are used throughout this book in editorial fashion only. No such use, or the use of any trade name, is intended to convey endorsement or other affiliation with the book. Copyrights of any screen captures in this book are the property of the software’s manufacturer.

DISCLAIMER

ComputerPREP, Inc. makes a sincere effort to ensure the accuracy of the material described herein; however, ComputerPREP, Inc. makes no warranty, express or implied, with respect to the quality, correctness, reliability, currentness, accuracy, or freedom from error of this document or the products it describes. ComputerPREP, Inc. makes no representation or warranty with respect to the contents hereof and specifically disclaims any implied warranties of fitness for any particular purpose. ComputerPREP, Inc. disclaims all liability for any direct, indirect, incidental, consequential, special, or exemplary damages resulting from the use of the information in this document or from the use of any products described in this document. Mention of any product does not constitute an endorsement by ComputerPREP, Inc. of that product. Data used in examples and sample data files are intended to be fictional. Any resemblance to real persons or companies is entirely coincidental.

ComputerPREP, Inc. makes every effort to ensure the accuracy of URLs referenced in all our materials, but we can not guarantee that all will be available throughout the life of the course.

When this manual/disk was published, all URLs were checked for accuracy and completeness.

However, due to the ever-changing nature of the Internet, some URLs may no longer be available or may have been re-directed.

COPYRIGHT NOTICE

This Guide is copyrighted and all rights are reserved by ComputerPREP, Inc. No part of this publication may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any language or computer language, in any form or by any means, electronic, mechanical, magnetic, optical, chemical, manual, or otherwise, without the prior written permission of ComputerPREP, Inc., 410 North 44th Street, Suite 600, Phoenix, Arizona 85008.

Copyright © 2000 - 2002 by ComputerPREP, Inc.

All Rights Reserved

ISBN: 0-7423-1905-9

iii

Table of Contents

Course Description ...............................................................................................xiii

ComputerPREP Courseware...................................................................................xv

Course Objectives .................................................................................................xv

Classroom Setup ................................................................................................. xvii

Lesson 1: Overview ............................................................................................. 1-1

Pre-Assessment Questions................................................................................... 1-2

Introduction ...................................................................................................... 1-3

Local Area Networks ........................................................................................... 1-4

LAN Advantages................................................................................................. 1-7

LAN Elements .................................................................................................... 1-9

LAN Users ........................................................................................................1-12

The LAN Market ................................................................................................1-13

Lesson Summary ..............................................................................................1-15

Lesson 1 Review ...............................................................................................1-17

Lesson 2: Topologies .......................................................................................... 2-1


Introduction ...................................................................................................... 2-3

Bus Topologies .................................................................................................. 2-3

Ring Topologies ................................................................................................. 2-8

Tree Topologies ................................................................................................2-11

Star Topologies.................................................................................................2-13

Mesh Topology..................................................................................................2-18

Wireless (Cell) Topology.....................................................................................2-20

Hybrid Topologies..............................................................................................2-23

Lesson Summary ..............................................................................................2-24

Lesson 2 Review ...............................................................................................2-26

Lesson 3: Information Transfer........................................................................... 3-1


Data Transport and Protocols ............................................................................... 3-3

Access Method Overview ..................................................................................... 3-7

CSMA/CD (Ethernet)........................................................................................... 3-9

Token Ring.......................................................................................................3-17

Token Bus........................................................................................................3-24

Summary.........................................................................................................3-25

Lesson Summary ..............................................................................................3-27

Lesson 3 Review ...............................................................................................3-29

Lesson 4: Transmission Techniques .................................................................... 4-1


Analog and Digital Transmissions.......................................................................... 4-3

Baseband Transmission....................................................................................... 4-5

Broadband Transmission ..................................................................................... 4-7

Hybrids............................................................................................................4-12

Fiber Optic Transmission ....................................................................................4-13

Wireless Transmission........................................................................................4-14

Comparison......................................................................................................4-15

Lesson Summary ..............................................................................................4-16

© 2000 - 2002 ComputerPREP, Inc. All Rights Reserved.

iv

Lesson 4 Review ...............................................................................................4-18

Lesson 5: Transmission Media............................................................................. 5-1


Overview of Transmission Media........................................................................... 5-3

Twisted Pair Cable.............................................................................................. 5-6

Coaxial Cable....................................................................................................5-15

Fiber Optic Cable...............................................................................................5-18

Infrared ...........................................................................................................5-24

Short-Range Wireless ........................................................................................5-26

Microwave........................................................................................................5-28

Satellite ...........................................................................................................5-31

Lesson Summary ..............................................................................................5-35

Lesson 5 Review ...............................................................................................5-38

Lesson 6: LAN Standards.................................................................................... 6-1


The Elements of a LAN Standard .......................................................................... 6-3

OSI Reference Model .......................................................................................... 6-5

TCP/IP.............................................................................................................. 6-9

SNA ................................................................................................................6-12

IEEE Committees ..............................................................................................6-14

IEEE 802.x Standards ........................................................................................6-16

Lesson Summary ..............................................................................................6-30

Lesson 6 Review ...............................................................................................6-32

Lesson 7: LAN Components ................................................................................ 7-1


Networking Components ..................................................................................... 7-3

Servers............................................................................................................. 7-7

Network Operating System (NOS) .......................................................................7-17

Local Networking Components ............................................................................7-22

Internetworking Components ..............................................................................7-25

Lesson Summary ..............................................................................................7-33

Lesson 7 Review ...............................................................................................7-36

Lesson 8: Network Management ......................................................................... 8-1


Network Trends ................................................................................................. 8-3

Network Management ......................................................................................... 8-7

User Management .............................................................................................8-21

Network Hardware and Software Management.......................................................8-23

Functional Areas of Network Management.............................................................8-33

Management Protocols .......................................................................................8-46

Planning a Network ...........................................................................................8-53

Lesson Summary ..............................................................................................8-57

Lesson 8 Review ...............................................................................................8-59

Lesson 9: Advanced LAN Technologies ................................................................ 9-1


From LANs to WAN ............................................................................................. 9-3

Basic WAN Technologies...................................................................................... 9-5

Advanced WAN Technologies ..............................................................................9-17

Frame Relay .....................................................................................................9-18

SONET.............................................................................................................9-20


v

Cell Relay: ATM/SMDS/BISDN.............................................................................9-25

Virtual Private Networks(VPNs) ...........................................................................9-36

Lesson Summary ..............................................................................................9-37

Lesson 9 Review ...............................................................................................9-40

Glossary ...................................................................................................Glossary-1

Index ........................................................................................................... Index-1

List of Figures

Figure 1-1: Local Area Networks ............................................................................. 1-3

Figure 1-2: Dumb Terminal and Mainframe Link ........................................................ 1-4

Figure 1-3: Local Area Networks (LANs) ................................................................... 1-5

Figure 1-4: Wide Area Networks (WANs) .................................................................. 1-5

Figure 1-5: Mainframe Architecture ......................................................................... 1-6

Figure 1-6: Modems in Mainframe Networks ............................................................. 1-7

Figure 1-7: LAN Shared Resources .......................................................................... 1-8

Figure 1-8: Shared Databases ................................................................................ 1-8

Figure 1-9: LAN E-Mail........................................................................................... 1-8

Figure 1-10: File Sharing ....................................................................................... 1-9

Figure 1-11: LAN Elements..................................................................................... 1-9

Figure 1-12: Fiber Optic and Wireless LAN Technology ..............................................1-11

Figure 1-13: LAN-to-LAN Connection ......................................................................1-11

Figure 1-14: Networking LAN Locations ...................................................................1-12

Figure 1-15: LAN Architecture................................................................................1-13

Figure 1-16: LAN Connectivity ...............................................................................1-14

Figure 2-1: LAN Topologies .................................................................................... 2-3

Figure 2-2: Bus Topology ....................................................................................... 2-4

Figure 2-3: Ethernet LAN ....................................................................................... 2-5

Figure 2-4: Advantages of Bus Topology .................................................................. 2-6

Figure 2-5: Disadvantages of Bus Topology .............................................................. 2-7

Figure 2-6: Token Ring and FDDI Ring Topologies...................................................... 2-8

Figure 2-7: Token Ring Topology............................................................................. 2-9

Figure 2-8: Advantages of Ring Topology ................................................................2-10

Figure 2-9: Disadvantages of Ring Topology ............................................................2-11

Figure 2-10: Tree Topology ...................................................................................2-12

Figure 2-11: Advantage of Tree Topology ................................................................2-12

Figure 2-12: Disadvantages of Tree Topology...........................................................2-13

Figure 2-13: Star Topology....................................................................................2-14

Figure 2-14: Advantages of Star Topology ...............................................................2-15

Figure 2-15: Linked Hubs in Star Topologies ............................................................2-16

Figure 2-16: Disadvantages of Star Topology ...........................................................2-17

Figure 2-17: Mesh Topology ..................................................................................2-18

Figure 2-18: Advantage of Mesh Topology ...............................................................2-19

Figure 2-19: Disadvantages of Mesh Topology..........................................................2-19

Figure 2-20: Wireless Topology..............................................................................2-20

Figure 2-21: Wireless Topology Access Point............................................................2-21

Figure 2-22: Advantages of Wireless Topology .........................................................2-21

Figure 2-23: Disadvantages of Wireless Topology .....................................................2-22

Figure 2-24: Hybrid Topology ................................................................................2-23

Figure 3-1: Packets and Frames .............................................................................. 3-3

Figure 3-2: Packet Structure................................................................................... 3-3


vi

Figure 3-3: HDLC Frame Structure .......................................................................... 3-4

Figure 3-4: Hybrid Network .................................................................................... 3-4

Figure 3-5: OSI Reference Model............................................................................. 3-5

Figure 3-6: Frame Using OSI Reference Model .......................................................... 3-5

Figure 3-7: OSI Layer Sending End Layer Functions ................................................... 3-6

Figure 3-8: OSI Layer 2 Function ............................................................................ 3-6

Figure 3-9: OSI Receiving End Layer Functions ......................................................... 3-7

Figure 3-10: LAN Access Methods............................................................................ 3-7

Figure 3-11: Ethernet ............................................................................................ 3-8

Figure 3-12: Token Ring ........................................................................................ 3-8

Figure 3-13: CSMA/CD (Ethernet) ........................................................................... 3-9

Figure 3-14: Ethernet Collision Detection.................................................................3-10

Figure 3-15: CSMA/CD—Contention Access Method...................................................3-10

Figure 3-16: Reduced Throughput With Ethernet ......................................................3-11

Figure 3-17: CSMA/CA..........................................................................................3-11

Figure 3-18: Wireless Networks Use Collision Avoidance ............................................3-12

Figure 3-19: Physical Star Configuration With Hub ....................................................3-13

Figure 3-20: Physical Star With Logical Bus Configuration ..........................................3-14

Figure 3-21: Intelligent Hub ..................................................................................3-14

Figure 3-22: Switching Hub ...................................................................................3-15

Figure 3-23: Virtual LAN .......................................................................................3-16

Figure 3-24: Switches Supporting Multiple Bandwidths ..............................................3-17

Figure 3-25: Token Ring With Four Stations.............................................................3-17

Figure 3-26: Token Ring With Active Monitor ...........................................................3-18

Figure 3-27: Token Ring With Busy Token ...............................................................3-19

Figure 3-28: Token With User Data Becomes A Frame ...............................................3-19

Figure 3-29: Destination Station Receives Token ......................................................3-20

Figure 3-30: Destination Station Sets Copy Bit On The Token.....................................3-20

Figure 3-31: Sending Station Sets Token to “Free” ...................................................3-21

Figure 3-32: Active and Passive Station Access ........................................................3-21

Figure 3-33: Token Ring Performance Does Not Degrade ...........................................3-22

Figure 3-34: Media Access Unit (MAU) ....................................................................3-23

Figure 3-35: Switching MAU ..................................................................................3-23

Figure 3-36: Token Bus ........................................................................................3-24

Figure 3-37: High-Priority Bus Stations Assigned Multiple Addresses ...........................3-25

Figure 4-1: Signals in the Network .......................................................................... 4-3

Figure 4-2: Analog Signal....................................................................................... 4-3

Figure 4-3: Digital Signal ....................................................................................... 4-4

Figure 4-4: Broadband Signal ................................................................................. 4-4

Figure 4-5: Baseband Signal................................................................................... 4-4

Figure 4-6: Analog Signals are Easily Digitized .......................................................... 4-5

Figure 4-7: CSMA and Token Passing Baseband Transmission...................................... 4-5

Figure 4-8: Advantages of Baseband Transmission..................................................... 4-6

Figure 4-9: Disadvantages of Baseband Transmission ................................................ 4-7

Figure 4-10: Broadband LAN Tree Configuration ........................................................ 4-7

Figure 4-11: Broadband Provides Separate Channels.................................................. 4-8

Figure 4-12: Head-End Controls Broadband Channels................................................. 4-8

Figure 4-13: Head-End in Tree Configuration ............................................................ 4-9

Figure 4-14: Broadband Signal Divided into 6-MHz Slices............................................ 4-9

Figure 4-15: Dual Cable Layout in Broadband ........................................................... 4-9

Figure 4-16: Advantages of Broadband Transmission ................................................4-10

Figure 4-17: Disadvantages of Broadband Transmission ............................................4-11

Figure 4-18: Hybrid Systems .................................................................................4-12


vii

Figure 4-19: Fiber Optic Transmission.....................................................................4-13

Figure 4-20: Fiber Divided into Channels .................................................................4-13

Figure 4-21: SONET Bit Rates ................................................................................4-14

Figure 4-22: Wireless Transmission ........................................................................4-14

Figure 5-1: Network Using Satellite ......................................................................... 5-3

Figure 5-2: Factors Influencing Network Design......................................................... 5-4

Figure 5-3: Types of Cable ..................................................................................... 5-4

Figure 5-4: Satellite Transmission ........................................................................... 5-5

Figure 5-5: Star Configuration Using Twisted Pair ...................................................... 5-6

Figure 5-6: Twisted Pair Cable ................................................................................ 5-6

Figure 5-7: Twisted Pair Cable Affected by Crosstalk .................................................. 5-7

Figure 5-8: Benefits of Tight and Loose Twisted Pair Cable.......................................... 5-7

Figure 5-9: Electromagnetic Interference (EMI) ......................................................... 5-8

Figure 5-10: Radio Frequency Interference (RFI) ....................................................... 5-8

Figure 5-11: Shielded Twisted Pair Cable.................................................................. 5-9

Figure 5-12: Unshielded Twisted Pair (UTP) .............................................................5-10

Figure 5-13: American Wire Gauge Standard ...........................................................5-10

Figure 5-14: Relationship Between Gauge and Attenuation ........................................5-11

Figure 5-15: Networks Using Voice Grade and Data Grade .........................................5-12

Figure 5-16: Using UTP Cable ................................................................................5-12

Figure 5-17: Using STP Cable ................................................................................5-14

Figure 5-18: Networks Using Coaxial Cable..............................................................5-15

Figure 5-19: Coaxial Cable ....................................................................................5-15

Figure 5-20: Coaxial Cable Carries Digital Signals .....................................................5-16

Figure 5-21: Coaxial Cable Uses Radio Grade Cable Standard.....................................5-16

Figure 5-22: Thin Coaxial Cable .............................................................................5-17

Figure 5-23: Thick Coaxial Cable ............................................................................5-17

Figure 5-24: Coaxial Cable Transmission Limits ........................................................5-18

Figure 5-25: Fiber Optic Ring.................................................................................5-18

Figure 5-26: Fiber Optic Cable ...............................................................................5-19

Figure 5-27: Single Mode and Multimode Fibers........................................................5-20

Figure 5-28: Smearing in Fiber Optic Cable..............................................................5-20

Figure 5-29: Comparison of Single Mode and Multimode Fiber ....................................5-21

Figure 5-30: Fiber Optic Light Source and Receiver ...................................................5-21

Figure 5-31: Fiber Optic Cable Uses Light Pulses ......................................................5-22

Figure 5-32: Frequency of LED and Laser Light Sources.............................................5-22

Figure 5-33: Comparison of LED and Laser Light Sources...........................................5-23

Figure 5-34: SLM Versus MLM Lasers ......................................................................5-23

Figure 5-35: Infrared Laptop .................................................................................5-24

Figure 5-36: Network With Infrared Devices ............................................................5-25

Figure 5-37: Short-Range Wireless Network.............................................................5-26

Figure 5-38: Transmission Rates of Short-Range Wireless Networks ............................5-27

Figure 5-39: FHSS and DSSS Encoding Methods.......................................................5-27

Figure 5-40: Microwave Network ............................................................................5-28

Figure 5-41: Distance Limits of Microwave Transmissions ..........................................5-29

Figure 5-42: LECs and IXCs Use Microwave Transmission ..........................................5-29

Figure 5-43: Microwave Transmission Between Buildings ...........................................5-30

Figure 5-44: Disadvantages of Microwave Networks..................................................5-30

Figure 5-45: Satellite Does Not Require Line of Sight ................................................5-31

Figure 5-46: Components of a Satellite Network.......................................................5-32

Figure 5-47: Orbits of GEOs, MEOs, and LEOs ..........................................................5-33

Figure 5-48: Transponders in a Satellite ..................................................................5-33

Figure 5-49: The Transmission Process in a Satellite Network.....................................5-34


viii

Figure 6-1: Local Area Network (LAN) ...................................................................... 6-3

Figure 6-2: Hybrid LAN .......................................................................................... 6-3

Figure 6-3: Bus and Ring LAN Configurations ............................................................ 6-4

Figure 6-4: IEEE Committees.................................................................................. 6-4

Figure 6-5: Digital Signal ....................................................................................... 6-4

Figure 6-6: Frame Structure ................................................................................... 6-5

Figure 6-7: OSI Reference Model............................................................................. 6-5

Figure 6-8: 802.x Standards Contained in OSI Layers 1 and 2 ..................................... 6-6

Figure 6-9: OSI Model Sending Process.................................................................... 6-7

Figure 6-10: OSI Model Receiving Process ................................................................ 6-8

Figure 6-11: OSI Reference Model Transmission Process............................................. 6-8

Figure 6-12: Complex LAN Network ......................................................................... 6-9

Figure 6-13: Comparison of OSI Model and TCP/IP .................................................... 6-9

Figure 6-14: TCP/IP Network Access Layer ..............................................................6-10

Figure 6-15: TCP/IP Internet Layer.........................................................................6-10

Figure 6-16: TCP/IP Host-to-Host Layer ..................................................................6-11

Figure 6-17: TCP/IP Process Layer..........................................................................6-11

Figure 6-18: Comparison of SNA and the OSI Model..................................................6-12

Figure 6-19: SNA Logical Services ..........................................................................6-12

Figure 6-20: Physical Services ...............................................................................6-13

Figure 6-21: Complex LAN Network ........................................................................6-14

Figure 6-22: IEEE 802.x Committees Develop Standards for OSI Layers 1 and 2 ...........6-14


Figure 6-24: OSI Data Link Layer Relates to the LLC and MAC Protocols ......................6-16

Figure 6-25: IEEE 802.2 Incorporated in OSI Layer 2 ................................................6-17


Figure 6-27: 10BaseT Supports 10 Mbps Over Twisted Pair ........................................6-18

Figure 6-28: 10BaseT and 100BaseT are Compatible.................................................6-19

Figure 6-29: IEEE 802.3 Rates Will Increase to 1Gbs.................................................6-20

Figure 6-30: IEEE 802.4 Token Bus Standard...........................................................6-20

Figure 6-31: IEEE 802.5 Token Ring Standard..........................................................6-21

Figure 6-32: IEEE 802.6 Distributed Queue Dual Bus ................................................6-21

Figure 6-33: IEEE 802.7 Broadband Transmission Standard .......................................6-22

Figure 6-34: IEEE 802.8 Fiber Distributed Data Interface (FDDI) ................................6-22

Figure 6-35: Copper Distributed Data Interface (CDDI) .............................................6-23

Figure 6-36: IEEE 802.9 Integrated Services............................................................6-23

Figure 6-37: IEEE 802.10 LAN Security ...................................................................6-24

Figure 6-38: IEEE 802.11 Wireless LANs .................................................................6-24

Figure 6-39: IEEE 802.11b Supports Ad Hoc and Infrastructure Models........................6-25

Figure 6-40: IEEE 802.12 100VG-AnyLAN................................................................6-26

Figure 6-41: 100VG Parent and Child Hubs ..............................................................6-26

Figure 6-42: 100VG Has Unique MAC Layer .............................................................6-27

Figure 6-43: IEEE 802.14 Cable TV Broadband Services ............................................6-28

Figure 6-44: IEEE 802.15 Wireless Personal Area Network (WPAN) .............................6-28

Figure 6-45: IEEE 802.16 Broadband Wireless Networking .........................................6-29

Figure 7-1: Complex LAN Network........................................................................... 7-3

Figure 7-2: Server ................................................................................................ 7-3

Figure 7-3: Physical Ring With Multiple Servers ......................................................... 7-4

Figure 7-4: Peer-to-Peer Network............................................................................ 7-5

Figure 7-5: Networks Use a Variety of Media............................................................. 7-6

Figure 7-6: Network Interface Card ......................................................................... 7-7

Figure 7-7: Server ................................................................................................ 7-7

Figure 7-8: Disk Server ......................................................................................... 7-8


ix

Figure 7-9: File Server........................................................................................... 7-8

Figure 7-10: File Servers Provide Centralized Storage and Security .............................. 7-9

Figure 7-11: Database Server................................................................................7-10

Figure 7-12: Database Servers Use Shared Locks or Exclusive Locks ...........................7-11

Figure 7-13: Structured Query Language (SQL)........................................................7-12

Figure 7-14: Print Server ......................................................................................7-12

Figure 7-15: Printer Acting as a Print Server ............................................................7-13

Figure 7-16: Application Server..............................................................................7-14

Figure 7-17: Communication Server .......................................................................7-15

Figure 7-18: Communication Server Connected to the Internet...................................7-16

Figure 7-19: Internet Server .................................................................................7-16

Figure 7-20: Gateway Server.................................................................................7-17

Figure 7-21: Network Operating System (NOS) ........................................................7-17

Figure 7-21: NOSs Provide Resource Sharing and User Logon Controls ........................7-18

Figure 7-22: Redundant Array of Inexpensive Disks (RAID) 5.....................................7-19

Figure 7-23: Disk Mirroring ...................................................................................7-19

Figure 7-24: Disk Duplexing ..................................................................................7-20

Figure 7-25: RAID 5 Uses Multiple Hard Disks ..........................................................7-20

Figure 7-26: Disk Caching .....................................................................................7-21

Figure 7-27: Elevator Seeking................................................................................7-21

Figure 7-28: Physical Ring With Multiple Servers ......................................................7-22

Figure 7-29: Network Adaptor ...............................................................................7-22

Figure 7-30: Physical Ring With Multiple Servers ......................................................7-23

Figure 7-31: LANs connected With Repeaters ...........................................................7-24

Figure 7-31: Repeater Regenerates Signals to Extend Signal Range ............................7-24

Figure 7-32: Multiport Repeater (MPR)....................................................................7-25

Figure 7-33: Complex Network With Bridge, Router, and Gateway ..............................7-25

Figure 7-34: Bridge, Router, and Gateway...............................................................7-26

Figure 7-35: Physical Rings Connected With a Bridge ................................................7-26

Figure 7-36: Bridges Operate at the MAC Sublayer of the OSI Data Link Layer..............7-27

Figure 7-37: Bridges Segregate Traffic Between Two Network Segments......................7-27

Figure 7-38: Multiport Bridges Connect LANs With Different Architecture and Cabling ....7-28

Figure 7-39: Physical Rings Connected With Routers .................................................7-28

Figure 7-40: Routers Operate at the Network Layer of the OSI Model ..........................7-29

Figure 7-41: Routers Must Know Each Network’s Addresses to Route Packets ...............7-30

Figure 7-42: Gateway...........................................................................................7-30

Figure 7-43: Gateways Operate at the Transport Layer of the OSI Model .....................7-31

Figure 7-44: Brouters Combine the Functionality of Bridges and Routers......................7-31

Figure 8-1: Complex Local Area Network .................................................................. 8-3

Figure 8-2: Simple Local Area Network .................................................................... 8-3

Figure 8-3: Heterogeneous Local Area Network ......................................................... 8-4

Figure 8-4: LANs Can be Connected Across the Country ............................................. 8-4

Figure 8-5: LAN Users Have Different Needs ............................................................. 8-5

Figure 8-6: LANs Interconnected With Satellite.......................................................... 8-5

Figure 8-7: Physical Ring With Multiple Servers ......................................................... 8-6

Figure 8-8: Network Management ........................................................................... 8-7

Figure 8-9: Software Distribution in a Physical Ring ................................................... 8-8

Figure 8-10: Software Distribution is Complex in Enterprise LANs ................................ 8-9

Figure 8-11: Software Distribution Using a Distribution Server .................................... 8-9

Figure 8-12: File Location Management Using File Servers .........................................8-10

Figure 8-13: Workstation Configuration Includes Several Facets .................................8-10

Figure 8-14: Individual Configuration Settings Available from Any Workstation .............8-11

Figure 8-15: Capacity for Extension is a Critical Network Issue ...................................8-12


x

Figure 8-16: Monitor Network Usage to Avoid Overload .............................................8-13

Figure 8-17: Management Traffic Can Contribute to Network Overload ........................8-14

Figure 8-18: Flexibility Allows a Network to Respond to the Unexpected.......................8-15

Figure 8-19: Firewalls Offer Protection for Network Internet Connections .....................8-16

Figure 8-20: There are Several Network Management Methods...................................8-16

Figure 8-21: Distributed Network Management ........................................................8-17

Figure 8-22: Protocol Standards Ensure Compatibility ...............................................8-18

Figure 8-23: Test Points Facilitate Monitoring and Maintenance...................................8-19

Figure 8-24: Additional Network Management Issues Exist for WANs ...........................8-20

Figure 8-25: User Management is Important to Network Management .........................8-21

Figure 8-26: User Management Involves Names, Passwords, and Access Rights ............8-22

Figure 8-27: Responding to User Questions Can be Time-Consuming...........................8-23

Figure 8-28: Network Hardware and Software Management Involves Several Tools .......8-23

Figure 8-29: More Complex Networks Require Higher-Level Management Tools.............8-24

Figure 8-30: Physical Layer Tools ...........................................................................8-24

Figure 8-31: Time-Domain Reflectometer (TDR) .......................................................8-25

Figure 8-32: TDRs Locate Media Problems, Faulty Connections, Cut Cables ..................8-25

Figure 8-33: TDRs and OTDRs Can Drastically Reduce Time Required for Diagnosis .......8-26

Figure 8-34: Network Monitoring Tools....................................................................8-26

Figure 8-35: Traffic Overload Alarms are Examples of Network Monitoring Tools ...........8-27

Figure 8-36: Network Analysis Tools Provide Extensive Quantitative Data ....................8-28

Figure 8-37: Data About Printer Use Can Determine the Need for Additional Printers .....8-28

Figure 8-38: Network Analysis Can Identify Traffic from Unknown Sources...................8-29

Figure 8-39: Workstations Send System Information to the Network Analyzer ..............8-30

Figure 8-40: Integrated Network Management .........................................................8-30

Figure 8-41: SNMP, DMI, and CMIP are the Three Major Protocol Families ....................8-32

Figure 8-43: Network Analysis Uses ISO Functional Areas 1 and 3 ..............................8-33

Figure 8-44: Five ISO Network Management Functional Areas ....................................8-33

Figure 8-45: Configuration Management..................................................................8-34

Figure 8-46: Configuration Management Involves Network Hardware and Software .......8-34

Figure 8-47: Fault Management .............................................................................8-35

Figure 8-48: Collision Tracking is Part of Fault Management .......................................8-35

Figure 8-49: Fault Management Can Require Hypothesis Testing.................................8-36

Figure 8-50: Advanced Fault Detection Can Reduce the Need for Hypothesis Testing .....8-37

Figure 8-51: Performance Management...................................................................8-37

Figure 8-52: Baselining Provides Overview of Typical Performance ..............................8-38

Figure 8-53: Comparison of Baseline and Current Performance Reveals Fault Source .....8-39

Figure 8-54: Polling Nodes is an Example of Real-Time Performance Management.........8-39

Figure 8-55: Accounting Management .....................................................................8-40

Figure 8-56: Accounting Information Used to Bill Departments for Network Time ..........8-41

Figure 8-57: Security Management.........................................................................8-41

Figure 8-58: Servers Can be Protected by Restricting Access......................................8-42

Figure 8-59: Unauthorized Tapping Can be Done Physically or Remotely ......................8-43

Figure 8-60: Different Users Have Different Access ...................................................8-43

Figure 8-61: Encryption Can Protect Data From Users Without the Key ........................8-44

Figure 8-62: Data Systems Perform Management Functions at Specified Intervals.........8-45

Figure 8-63: SNMP, DMI, and CMIP Define How Data is Transferred ............................8-46

Figure 8-64: Protocols Work With MIB and SMI ........................................................8-47

Figure 8-65: Network Elements Defined and Monitored by Management Stations ..........8-47

Figure 8-66: Protocol is Used to Move Information Across the Network ........................8-48

Figure 8-67: Simple Network Management Protocol (SNMP) .......................................8-48

Figure 8-68: SNMP Requests One Record at a Time ..................................................8-49

Figure 8-69: Desktop Management Interface (DMI) ..................................................8-50


xi

Figure 8-70: DMI Consists of the Service Layer, CI, MIF, and MI.................................8-50

Figure 8-71: DMI Handles All Tasks Using the Same Process ......................................8-51

Figure 8-72: Common Management Information Protocol (CMIP) ................................8-51

Figure 8-73: Network Managers Have a Choice of Management Protocols.....................8-52

Figure 8-74: Networks May Use More Than One Management Protocol.........................8-52

Figure 8-75: Heterogeneous Interconnected Network ................................................8-53

Figure 8-76: Determining the Needs of the Users is the First Step in Network Planning ..8-54

Figure 8-77: Look at the Needs of Each Workgroup, Then Tie Them Together ...............8-54

Figure 8-78: Focus on Common Elements in Networks ..............................................8-55

Figure 8-79: There are Many Advantages to Interconnection ......................................8-56

Figure 9-1: Wide Area Network (WAN) ..................................................................... 9-3

Figure 9-2: Small Local Area Network (LAN) ............................................................. 9-4

Figure 9-3: Metropolitan Area Network (MAN) ........................................................... 9-4

Figure 9-4: Wide Area Network (WAN) Using Satellite ................................................ 9-5

Figure 9-5: WANs Use Many Different Connection Methods ......................................... 9-5

Figure 9-6: WAN Connected Over the PSTN Using Modems ......................................... 9-6

Figure 9-7: WAN Connected Using Leased T1 Circuits................................................. 9-6

Figure 9-8: International WAN Using T1 Links ........................................................... 9-7

Figure 9-9: T1 Uses Twisted Pair, T3 Uses Twisted Pair or Fiber Optic ........................... 9-8

Figure 9-10: T1 Connection Using a Single Channel ................................................... 9-8

Figure 9-11: T1 Using Separate Channels for Voice, Video, and Data............................ 9-9

Figure 9-12: Comparison of Bandwidth Required for FT1, T1, and T3............................ 9-9

Figure 9-13: Statistical Multiplexing Provides Bandwidth Based On Demand .................9-10

Figure 9-14: Statistical Multiplexing Conserves Bandwidth .........................................9-10

Figure 9-15: FT1 Requires Two T1 DS0 Channels, One for Voice and One for Data.........9-11

Figure 9-16: Voice Line Is In Use During the Day, While the Data Line Is Used at Night .9-11

Figure 9-17: Voice and Data Use the Same Channel, Based on Demand.......................9-12

Figure 9-18: Packet-Switching Network...................................................................9-12

Figure 9-19: Packets are Routed Based on Address Information..................................9-12

Figure 9-20: X.25 Can Accommodate Various Packet Protocols ...................................9-13

Figure 9-21: An X.25 Gateway Connects a LAN to the Public Network ..........................9-14

Figure 9-22: Integrated Services Digital Network (ISDN) ...........................................9-14

Figure 9-23: ISDN can be Implemented as PRI or BRI ...............................................9-15

Figure 9-24: ISDN Uses a Single Phone Line for Voice, Data, Video, and Fax ................9-15

Figure 9-25: ISDN Connects Telecommuters to Their Office LANs................................9-16

Figure 9-26: Advanced WAN Technologies ...............................................................9-17

Figure 9-27: Frame Relay, Cell Relay, and SONET are OSI-Compliant ..........................9-18

Figure 9-28: Frame Relay Frames are Forwarded from Network to Network in Hops.......9-18

Figure 9-29: Error Checking in Frame Relay is Performed at the Destination Node .........9-19

Figure 9-30: One Switched Frame Relay Circuit Will Replace Many Dedicated Circuits ....9-19

Figure 9-31: Frame Relay is Not Optimized for Delay-Sensitive Traffic .........................9-20

Figure 9-32: Synchronous Optical Network (SONET) .................................................9-20

Figure 9-33: SONET Backbones Used for SMDS, BISDN, and Voice, Video, and Data......9-21

Figure 9-34: SONET ADMs Insert and Extract Payloads Without Multiplexing.................9-21

Figure 9-35: Synchronous Payload Envelope (SPE) Surrounded by STS Frame ..............9-22

Figure 9-36: Comparison of STS and the Digital Hierarchy .........................................9-22

Figure 9-37: Advantages of SONET.........................................................................9-23

Figure 9-38: SONET Backbone Supports ATM, SMDS, and BISDN Applications ..............9-23

Figure 9-39: SONET Ring With ADMs Surrounding Metropolitan Area ...........................9-24

Figure 9-40: SONET Can Reroute Traffic In the Opposite Direction If the Ring is Cut......9-25

Figure 9-41: Cell Relay Technologies ......................................................................9-25

Figure 9-42: Cell Relay Uses Fixed Frame Size to Control Delay ..................................9-25

Figure 9-43: SMDS, BISDN, and ATM are OSI-Compliant ...........................................9-26


xii

Figure 9-44: Asynchronous Transfer Mode (ATM)......................................................9-27

Figure 9-45: ATM Serves the Data Link Layer of the OSI Reference Model ....................9-27

Figure 9-46: Video and Voice Require Constant Data Rate .........................................9-28

Figure 9-47: ATM Provides Switching, and SONET Provides Physical Transport ..............9-29

Figure 9-48: ATM Handles Information at Faster Rates Than Other Technologies ...........9-29

Figure 9-49: ATM Can Handle Any Mix of Data, Video, and Voice Traffic .......................9-30

Figure 9-50: Switched Multimegabit Data Service (SMDS) .........................................9-31

Figure 9-51: SMDS Uses 53-Octet Cells...................................................................9-31

Figure 9-52: SMDS is a Connectionless Protocol .......................................................9-32

Figure 9-53: SMDS Switches Can be Used to Create Enterprise Networks.....................9-32

Figure 9-54: Broadband Integrated Services Digital Network (BISDN) .........................9-33

Figure 9-55: BISDN Addresses the Network Layer of the OSI Reference Model..............9-33

Figure 9-56: BISDN is Designed for Business and Residential Use ...............................9-34

Figure 9-57: BISDN Transports Information From Different Applications as Cells ...........9-34

Figure 9-58: BISDN Can be Used to Integrate Cell Relay With SONET Transport............9-34

Figure 9-59: BISDN Can Support Dial-Up Access and VPNs ........................................9-35

Figure 9-60: Virtual Private Networks (VPNs) ...........................................................9-36

Figure 9-61: VPN Tunnel .......................................................................................9-36


Course Description

Welcome to Local Area Networks (LANs) .

This course will help you prepare for the Certified in

Convergent Network Technologies (CCNT) exam, a program sponsored by the TIA 

(Telecommunications Industry Association).

This course is aimed at preparation and review for the Local Area Networks (LANs) module of the CCNT exam, as well as professional development for IT professionals. It is designed to be used in a lecture-based classroom setting.

Local Area Networks explains the concepts and technology of LAN topologies, information transfer, transmission techniques, media standards, network management, and the future of

LAN. This course has nine lessons, and each lesson covers several topics. Following are the nine lessons to the LANs course, along with the topics covered in each lesson. xiii


xiv

Topics Covered

Overview

• Introduction

• Local Area Networks

• LAN Advantages

• LAN Elements

• LAN Users

• The LAN Market

Topologies

• Introduction

• Bus Topologies

• Ring Topologies

• Tree Topologies

• Star Topologies

• Mesh Topology

• Wireless (Cell) Topology

• Hybrid Topologies

Information Transfer

• Data Transport and

Protocols

• Access Method

Overview

• CSMA/CD (Ethernet)

• Token Ring

• Token Bus

• Summary

Transmission Techniques LAN Components

• Analog and Digital

Transmissions

• Networking Components

• Servers

• Baseband Transmission

• Broadband Transmission

• NOS

• Hybrids

• Local Networking

Components

• Fiber Optic Transmission • Internetworking Components

• Wireless Transmission Network Management

• Comparison

Transmission Media

• Network Trends

• Network Management

• Overview

• Twisted Pair Cable

• Coaxial Cable

• User Management

• Network Hardware and

Software Management

• Functional Areas of Network

Management • Fiber Optic Cable

• Infrared

• Short-Range Wireless

• Microwave

•

•

Management Protocols

Planning a Network

Advanced LAN Technologies

• Satellite

LAN Standards

• The Elements of a LAN

Standard

• From LANs to WAN

• Basic WAN Technologies

• Advanced WAN Technologies

• OSI Reference Model

• TCP/IP

• SNA

• Frame Relay

• SONET

• Cell Relay:

ATM/SMDS/BISDN

• IEEE Committees

• IEEE 802.x Standards

• Virtual Private Networks

(VPNs)


ComputerPREP Courseware

This learning guide was developed for instructor-led training and will assist you during class.

Along with comprehensive instructional text and objectives checklists, this learning guide also includes pre-assessment questions, tech terms, and lesson summaries and reviews.

Each lesson in this course follows a regular structure, along with graphical cues to illustrate important terms and concepts. The structure of a typical module includes:

• Pre-Assessment Questions – Each lesson includes pre-assessment questions to test student’s understanding of the key concepts presented in the lesson.

• Objectives – Each lesson includes a list of objectives to set the stage for the rest of the lesson.

• Tech Terms – All terms that are defined throughout the text appear in bold font.

• Lesson Summary – The Lesson Summaries at the end of each lesson includes: an

Application Project to extend learning, a Skills Review of key concepts and objectives presented in the lesson, and Lesson Review Questions designed to test understanding.

• Glossary – The Glossary contains a list of key terms defined throughout the course, and can be used for self-study once the course has been completed.

• Table of Contents and Index – The Table of Contents appears at the beginning of the book, and the Index appears at the end. These can also be used to review key areas.

Course Objectives

• Describe network use before present-day LANs.

• Describe a present-day LAN.

• Identify the primary advantages provided by a LAN.

• Identify the basic elements of a LAN.

• Identify common user groups of LAN technology.

• Identify the primary issues confronting the LAN market.

• Identify the four LAN topologies.

• Describe the features and functions of bus topologies.

• Describe the features and functions of ring topologies.

• Describe the features and functions of tree topologies.

• Describe the features and functions of star topologies. xv


xvi

• Identify type of hubs and their features and functions.

• Describe basic data transport in a LAN.

• Describe the primary access methods for LANs.

• Describe the features and functions of CSMA/CD (ethernet) access method.

• Describe the features and functions of the token ring access method.

• Describe the features and functions of the token bus access method.

• Discuss the factors involved in choosing an access method.

• Describe the different types of signals that require transmission.

• Describe baseband transmission within a LAN.

• Describe broadband transmission within a LAN.

• Describe hybrid transmission techniques.

• Describe fiber optic transmission within a LAN.

• Describe wireless transmission techniques and their relationship to LAN technologies.

• Differentiate between the transmission techniques.

• Identify key considerations in selecting transmission media in networks.

• Identify the features, functions, and uses of twisted pair cable.

• Identify the features, functions, and uses of coaxial cable.

• Identify the features, functions, and uses of optical fiber cable.

• Identify the features functions, and uses of infrared transmission.

• Identify the features, functions and uses of short-range wireless transmission.

• Identify the features, functions, and uses of microwave transmission.

• Identify the features, functions, and uses of satellite transmission.

• Describe the current state of LAN standards.

• Describe the structure and function of the OSI reference model.

• Describe the TCP/IP network protocols.

• Describe the SNA network protocols.

• Describe the purpose of the IEEE committees.


• Identify IEEE 802.x standards.

• Describe components used in a network.

• Describe different types of network servers.

• Describe the features and functions of a network operating system (NOS).

• Describe the networking components used in a local LAN.

• Describe the internetworking components used in networking.

• Discuss network management trends.

• Discuss common network management issues.

• Discuss the issues involving network user management.

• Discuss tools available for network hardware and software management.

• Discuss the ISO network management functional areas.

• Discuss the role of network management protocols.

• Describe the issues surrounding network planning.

• Discuss the issues behind the development of new LAN technologies.

• Describe the basic WAN technologies.

• Describe advanced data transmission technologies.

• Describe frame relay technology.

• Describe SONET technology.

• Describe cell relay technology.

• Describe the significance of virtual private networks (VPNs) over the Internet to WANs.

Classroom Setup

Student computers are not required for this seminar course. If the instructor wants to deliver supplemental activities or quizzes electronically, computers that meet the instructor's needs will be required for each student. Otherwise, all supplemental material can be distributed as hard-copy documents and completed by students using a pen and paper. xvii


xviii


O

BJECTIVES

1

Lesson 1:

Overview

By the end of this lesson, you will be able to:

•

Describe network use before present-day LANs.

•

Describe a present-day LAN.

•

Compare and contrast basic LAN and WAN features.

•

Identify the key components of a

LAN.

•

Identify the primary advantages provided by a LAN.

•

Identify the basic elements of a

LAN.

•

Identify common LAN technologies.

•

Identify current issues confronting the LAN market.


1-2 Local Area Networks (LANs)

Pre-Assessment Questions

1. Unlike mainframe networks, LANs use ________ computing resources. a. Single b. Common c. Distributed d. Personal

2. True or false: An access method defines the way information is transported through the network.

_______________

3. Is the LAN market limited to corporate and other large environments, or more broad-based?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________


Lesson 1: Overview 1-3

Introduction

This course is about the basics of local area networks , or LANs. You will learn how LANs differ from their mainframe predecessors and what elements make up

LANs today.

Figure 1-1: Local Area Networks

 local area network (LAN)

A network providing data communication between computer stations, usually limited to a single building or complex of buildings.

As recently as 15 years ago, when a user worked on a network, it was most likely at a dumb terminal linked to a mainframe . LANs were still in their infancy and were being designed to match the mainframe environment as closely as possible.



Figure 1-2: Dumb Terminal and Mainframe Link

 dumb terminal

A computer terminal with limited capacity to manage either its own functions or the communication channel to the host computer.

 mainframe

A large, powerful central computer that performs the processing for a network of remote terminals.

Today, the "terminal" is almost exclusively a personal computer (PC) linked to a

LAN. Dumb terminals are rarely seen, and when required, are emulated through applications running on a PC.

 personal computer (PC)

A desktop computer system.

Local Area Networks

A LAN is a data communication network that pulls together computing resources such as PCs, printers, miniframes, and mainframes. These elements are linked by a transmission cable or other transmission media. It is common to find LANs consisting entirely of PCs, with some serving in roles traditionally restricted to minicomputers (sometimes called "miniframes") and mainframes.

Modern networks often include modems and other remote communication devices to support Internet access, remote user access, and remote LAN connectivity.


Lesson 1: Overview

 modem

MOdulator/DEModulator. Device that converts digital signals to analog signals for transmission on analog telephone lines.

1-5

Figure 1-3: Local Area Networks (LANs)

A defining quality of a LAN is its size. A LAN typically spans a limited geographic area, usually no more than a building or campus.

For larger areas, metropolitan area networks (MANs) or wide area networks

(WANs) are needed. MANs and WANs are connected with bridges and routers and generally use the public telephone network for transmission. The term MAN is not commonly seen, with the term WAN assumed to include the MAN designation.

Figure 1-4: Wide Area Networks (WANs)



 metropolitan area network (MAN)

A network with a physical extent of several miles—for example, a city and its suburbs. MANs are usually made of individual LANs linked with specialized hardware and telephone lines.

 wide area network (WAN)

A network with unlimited physical extent, such as cities on both coasts of the United States. Usually made of linked LANs or terminal-to-host networks.

The predecessors to the LAN were the early mainframe networks. Mainframe architecture is characterized by several terminals cabled to a single mainframe.

Without the mainframe, the individual terminal is worthless, because it has no memory or processor of its own.

Figure 1-5: Mainframe Architecture

Cable connections were limited in length because cables reach only so far.

Modems, however, let mainframe networks expand. Modems convert the computer’s digital signals to analog signals , which can be sent over the telephone network, connecting terminals hundreds of miles apart.

 digital signal

An electrical signal that varies in discrete steps.

 analog signal

An electrical signal that varies continuously in amplitude and frequency.



Figure 1-6: Modems in Mainframe Networks

Although some of these early networks grew very large, the basic architecture was the same: one host computer controlling many individual terminals.

The host computer processed all requests; the terminals did not have the ability to process any information, other than to send it to the host computer.

The growing popularity of the personal computer allowed improvement in the network area. Unlike a simple terminal, the personal computer provided a processor and considerable memory of its own.

With the advent of the personal computer, tasks could now be shared between the client and the server.

Departments that previously had to submit requests only to have them queued up for access to a mainframe began to demand personal computer power on the desktop.

Other departments wanted personal computer resources also. For many companies, personal computers proved an economical and popular upgrade to existing mainframe networks.

Ultimately, the result was LANs that were structured around distributed computing, characterized first by client/server applications and later by other

PC-oriented application models, rather than a single central mainframe. In some cases, each department developed its own LAN. Different LANs serve different purposes. It is not unusual to find several independent LANs within a single organization. Businesses link these LANs in increasingly large and complex networks.

 distributed computing

Application model in which application components—tasks that must be performed by the application—are shared by different computers on the network.

LAN Advantages

LANs enable the sharing of resources. Commonly shared resources include processing power, storage, printers, modems, and video telephone communications.



Figure 1-7: LAN Shared Resources

LANs also enable an organization to integrate functions and provide special services. LAN services can include shared databases, shared communication links, audio and video conferencing, Internet firewalls, and so on.

Figure 1-8: Shared Databases

LANs also provide efficient communication. The most common example is electronic mail , or e-mail. With e-mail, all users have a network address. Users can send memos or other messages to one individual or to a group of people. By linking the LAN to the Internet, e-mail can be used for easy, inexpensive worldwide communication.

Figure 1-9: LAN E-Mail



 electronic mail (e-mail)

A messaging system operating over a communications medium. E-mail is typically implemented through a specialized server and includes links to the Internet for external communications.

Another example of efficient communication is file sharing .

Two users can access and make changes to the same file. This is often one of the key reasons for initially implementing a LAN. Modern LANs can even enable offline access to files with automatic synchronization when the user connects to the LAN.

Figure 1-10: File Sharing

 file sharing

A feature of network operating systems that allows multiple users access to the same file.

LAN Elements

The simplest perception of a LAN is a collection of computers and peripherals that are connected. In fact, to many LAN users, that is all they need—and care— to know. But for even the simplest LAN to work well, many hardware and software elements are involved.

Figure 1-11: LAN Elements



 peripheral

Device on a network that provides input/output (such as printers) or auxiliary functions (such as data storage).

The components of a LAN help people do useful work or support the proper function of the network. A station is a terminal, personal computer, or workstation that gives the user access to the network. It is one type of node .

 node

Any device on the network other than the network cabling. Nodes include user stations, network servers, multiuser computers, bridges, routers, and gateways.

Some nodes are devices that transmit network data from one point to another or monitor a particular operation. An example might be a dedicated computer that monitors a factory operation and sends a report to another node, such as the operator’s station.

Other nodes include storage and output devices such as databases and printers.

The LAN's architecture refers to the overall structure and major characteristics of the network. These characteristics include:

• The network's topology —how the nodes are connected .

• The access method —how a node puts information onto the network .

• The transmission technique

—

how information passes through the network.

• The transmission media (cable or wireless transmission) used.

• The use of specific protocols (rules) defining communication between computers.

• The LAN's interconnectivity— how it shares information with other networks.

 topology

A description of the physical layout of a network.

 access method

A technique used by a node to place its signal on a network. Common

LAN access methods include CSMA/CD, CSMA/CA, and token passing.

 protocol

A formal set of rules. In a LAN context, a protocol refers to the standardized rules governing network functions that strongly influence the design of network components.



 interconnectivity

The ability to physically connect with other networks. Interconnectivity does not take into account whether information from one network can be understood by another.

As LAN technology has improved, ideas have changed. Optical fiber to the desktop was once thought to be both impractical and expensive, but many networks have migrated in that direction. Another popular option is wireless

LAN technology, which provides an added element of portability.

Figure 1-12: Fiber Optic and Wireless LAN Technology

Another example of improved technology is the connection of LANs over the public telephone network and other connection technologies. Standard telephone connections are typically considered too slow for most LAN-to-LAN applications, but are commonly used for remote user access.

Figure 1-13: LAN-to-LAN Connection



WAN connections are typically implemented through higher-speed, higherbandwidth links that provide better access to network data. One popular option is to use the Internet as a WAN backbone.

LAN Users

Some of the first distributed processing networks were set up in factories, with nodes monitoring and controlling automated manufacturing equipment and assembly lines. In the scientific community, similar LANs recorded data. Others facilitated communication between research teams in different geographic locations.

Figure 1-14: Networking LAN Locations

The "grandfather of LANs" was a data communication network called the

Advanced Research Projects Agency Network (ARPAnet), now part of what has grown to become the Internet.

The ARPAnet was (and the Internet is) a wide area network (WAN), because it connects a series of international computer networks.

Any time you connect two LANs together, you have a WAN.

From these humble beginnings, LANs have become both a standard and an expectation. Organizations that do not include a LAN as part of the computer support solution have become the exception. Many organizations have become completely dependent on their LANs as a way of doing business, with LAN failures bringing all work to a sudden halt.

Once unheard of (and unthinkable), home LANs are a fast growing part of the

LAN market. Improvements in LAN technologies, cost reductions in LAN hardware, and the integration of network support into most PC operating systems have helped to drive the growth of home LANs. One major influence on this growth is the desire to share a high-speed Internet connection, such as


Lesson 1: Overview 1-13 cable modems or digital subscriber line (DSL) modems, with all of the computers in a home. Satellite television operators have also recently started offering Internet access service.

 cable modem

Internet connection device that provide a high-speed shared Internet connection through existing cable television lines.

 digital subscriber line (DSL)

DSL or xDSL. A set of technologies that provides a low-cost, easily accessible, copper-based solution to the need for T1/E1 service. Some xDSL technologies are based on modems, whereas others are based on the use of a CSU/DSU.

The LAN Market

Because LANs were developed to respond to specific market needs, a variety of

LAN architectures are available, mostly incompatible. Vendors of LAN equipment generally design their hardware and software to fit the specifications of a particular LAN architecture.

Figure 1-15: LAN Architecture

User and corporate expectations in LAN connectivity have resulted in cooperative ventures among designers, vendors, and organizations that set standards for LAN architectures. Connectivity has become less an issue of which vendors you select than which LAN technologies you choose to


1-14 Local Area Networks (LANs) implement. You will learn about common LAN standards and their features in this course.

Figure 1-16: LAN Connectivity

 standards

Agreed-upon principles governing the design and implementation of hardware or software, including principles governing networking.

Though interoperability is key to the widespread use of LANs and WANs, not all standardization issues have been worked out. Work in the standards area is ongoing. LAN bandwidth continues to increase and costs continue to drop, but at the same time, user expectations continue to climb.

 interoperability

The ability of networks and/or network equipment to operate with one another.

Another important issue addressed by new architectures is speed. Like the early computers, early LANs were relatively slow. As users have become familiar with

LAN resources, they have demanded more. The newest LAN architectures, whether stand-alone or designed to be connected to high-speed WANs, offer more speed and more sophisticated capabilities.



Lesson Summary

Application project

Discuss the impact that remote access requirements and the growth of home networks might have on LAN standards currently under development. Consider the expectation of many users to be able to connect at any time or anywhere.

Skills review

Following are the key point presented in this lesson:

• As recently as 15 years ago, when a user worked on a network, it was most likely at a dumb terminal linked to a mainframe. Today, the "terminal" is almost exclusively a personal computer (PC ) linked to a LAN. Dumb terminals are rarely seen, and when required, are emulated through applications running on a PC.

• A LAN is a data communication network that links PCs, printers, minicomputers, and mainframes with a transmission cable or other transmission media.

• Modems convert the computer's digital signals to analog signals, which can be sent over the telephone network, connecting terminals hundreds of miles apart.

• Although early networks grew very large, the basic architecture was the same: one host computer controlling many individual terminals. Ultimately,

LANs were structured around distributed computing applications rather than a single central mainframe.

• LANs enable an organization to share resources and integrate functions.

LANs also provide efficient communication.

• Each node in a LAN is associated with a particular network task. A station is one type of node .

It is a terminal, personal computer, or workstation that gives the user access to the network. Other nodes include storage and output devices such as databases and printers.

• The LAN's architecture refers to the overall structure and major characteristics of the network. These characteristics include the network's topology, the access method, the transmission technique, the transmission media (cabling) used, the use of specific protocols, and the LAN's interconnectivity.

• Optical fiber to the desktop was once thought to be both impractical and expensive, but many networks have migrated in that direction. Another popular option is wireless LAN technology, which provides an added element of portability.



• WAN connections are typically implemented through higher-speed, higherbandwidth links that provide better access to network data. One popular option is to use the Internet as a WAN backbone.

• The "grandfather of LANs" was a data communication network called the

Advanced Research Projects Agency Network (ARPAnet), now part of what has grown to become the Internet. ARPAnet was, and the Internet is, a WAN, because it connects an international computer network.

• Improvements in LAN technologies, cost reductions in LAN hardware, and the integration of network support into most PC operating systems have helped to drive the growth of home LANs. One major influence on this growth is the desire to share a high-speed Internet connection, such as cable modems or digital subscriber line (DSL) modems, with all of the computers in a home.

• User and corporate expectations in LAN connectivity have resulted in cooperative ventures among designers, vendors, and organizations that set standards for LAN architectures. Connectivity has become less an issue of which vendors you select than which LAN technologies you choose to implement.

Now that you have completed this lesson, you should be able to:

Describe network use before present-day LANs.

Describe a present-day LAN.

Compare and contrast basic LAN and WAN features.

Identify the key components of a LAN.

Identify the primary advantages provided by a LAN.

Identify the basic elements of a LAN.

Identify common LAN technologies.

Identify current issues confronting the LAN market.



Lesson 1 Review

1. What are the main architectural components of a LAN?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

2. To what is the growth of LAN installations due?

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

__________________________________________________________________________

3. What are the various devices that make up a LAN, such as personal computer workstations, file servers, printers, etc., known as?

__________________________________________________________________________

__________________________________________________________________________




O

BJECTIVES

2

Lesson 2:

Topologies

By the end of this lesson, you will be able to:

•

Identify LAN topologies.

•

Describe the features and functions of bus topologies.

•

Describe the features and functions of ring topologies.

•

Describe the features and functions of tree topologies.

•

Describe the features and functions of star topologies.

•

Describe the features and functions of mesh topologies.

•

Describe the features and functions of wireless (cell) topologies.

•

Describe the identifying characteristic of a hybrid topology.



Pre-Assessment Questions

1. Which of the following is a disadvantage of bus topologies? a. Troubleshooting b. Nonstandard topology c. Does not support ethernet networks d. Moderate data speed

2. Which of the following is a disadvantage of wireless (cell) topologies? a. Cannot be integrated with other topologies b. Requires excessive amounts of cable bandwidth d. No defined standards

3. Which of the following uses coaxial cable terminated at each end? a. Star b. Ring c. Mesh d. Bus


Lesson 2: Topologies 2-3

Introduction

The topology, or layout, is the way all components of the LAN are physically linked. Common topologies include bus, ring, tree, star, mesh, and wireless. A hybrid topology may also be used, which is a combination of common topologies in a single network. A hub is a LAN component that creates a center for cable and network management.

Figure 2-1: LAN Topologies

Bus Topologies

The standard bus configuration is simple: All stations are connected via a single backbone cable, called a bus. Each node either is connected to the backbone cable by a drop cable and associated hardware or connects directly to the cable.

 bus

A network topology with all network nodes linked over a single communication path. All nodes have access to the bus and must contend for the communication path. The bus is most often used as the topology in the 802.3 (ethernet) or 802.4 (token bus) standard networks.



Figure 2-2: Bus Topology

The backbone cables are usually coaxial and generally have more shielding than the drop cables. The cable is terminated by a terminating resistor at each end.

This signal-dampening device prevents spurious reflection of signals. The backbone can be thought of as a single-lane "data highway," with all the data broadcast down the highway cable.

 coaxial cabling

Type of cable, usually composed of a single metallic conductor surrounded by a foam or dielectric insulator, a metallic foil or braid shield, and a protective jacket. The shield protects the conductor from crosstalk and other sources of noise.

Both twisted pair and coaxial cable require a transceiver at the node to translate the node’s signals into signals transmittable by the particular medium.

Ethernet and AppleTalk are bus-based networks. Because all the data from every node is sent down a single wire, only one message can be sent at a time.

Each node must have access to the network.

 ethernet

An access method using CSMA/CD. Closely related to the IEEE 802.3 standard but uses a slightly different frame structure.

 AppleTalk

A network protocol, using CSMA/CD access, for Apple and Macintosh computer networks.

The most common access method for bus topologies is Carrier Sense Multiple

Access (CSMA). When a node wants to send a message over the network, it puts the message on the bus. With CSMA, every node in the network receives every message, whether it is addressed to that node or not.

Collision detection (CD) and collision avoidance (CA) are alternative ways of handling the problems that occur when two nodes send messages simultaneously.



 collision detection (CD)

A way of preventing two stations on a contention-based network from simultaneously attempting access to the network. With collision detection, a station sends a data packet onto the network and then listens for a collision. A collision results in a random wait and then retransmission.

 collision avoidance (CA)

A way of preventing two stations on a contention-based network from simultaneously attempting access to the network. With collision avoidance, a station requesting access to the network transmits a preliminary "reservation" packet and then listens for a collision.

Ethernet LANs traditionally use a bus topology with CSMA/CD access. Because of its early development and widespread implementation, it has since become incorporated, with minor modification, as an Institute of Electrical and

Electronic Engineers ( IEEE ) 802.3 standard.

Figure 2-3: Ethernet LAN

Apple Computer's LocalTalk is uses CSMA/CA. One of the reasons for

CSMA/CA’s limited use is that it requires more transmission overhead than

CSMA/CD, limiting network performance.

 Institute of Electrical and Electronic Engineers (IEEE)

A professional organization for engineers that develops technical standards. IEEE LAN standards are the predominant LAN standards.


2-6

Advantages of Bus Topologies

Local Area Networks (LANs)

Figure 2-4: Advantages of Bus Topology

Bus topologies offer a number of advantages.

Low-cost cabling:

• Unstructured cabling is wired directly from node to node without passing through a hub or wiring center. The initial cost is lower, but expansion may require more rewiring.

Moderate data speeds:

• With coaxial or twisted pair cabling, a bus-based LAN can support data speeds up to 10 megabits per second ( Mbps ) in an office environment.

 megabits per second (Mbps)

A data rate of 1 million bits per second. LANs commonly operate in the

Mbps range.

Familiar technology:

• Bus topologies have been used for years. As a result, installation and troubleshooting techniques are well known, and tools and hardware components are readily available.

Limited failure:

• A failure of one node or drop cable on the network will not necessarily cripple the other nodes.


Lesson 2: Topologies

Disadvantages of Bus Topologies

2-7

Figure 2-5: Disadvantages of Bus Topology

When you consider bus topologies, it is important to be familiar with disadvantages that may influence the decision.

Extensive cabling:

• For even a simple layout, a lot of cabling is required. In addition, if a problem occurs anywhere on the backbone cable, all users risk losing network access. Some bus vendors have designed "self-terminating" links to minimize this problem.

Difficult troubleshooting:

• Specialized test equipment is required to locate cable faults. A fault anywhere in the cable disrupts communication for all nodes.

Signal interference:

• Generally, a minimum distance is required between adjacent drops to prevent signals from adjacent stations from interfering with each other.

Maximum cable length, maximum number of cable segments, maximum number of nodes, and node placement are defined by IEEE and ethernet standards.

Reconfiguration difficult:

• Adding a node typically requires first taking down the network.

Attenuation:

• Loss of signal strength due to attenuation can result in communication problems. Repeaters can be used to boost the signal, but will also boost any electronic signal "noise" on the cable.



 repeater

A device that regenerates signals at full strength. Used with digital signals, a repeater can remove the noise when regenerating the signal.

Used with analog signals, both the signal and noise are amplified. Also known as a regenerator, or line regeneration equipment (LRE).

 attenuation

Loss of signal strength over distance. Most transmission methods have some level of attenuation.

Ring Topologies

Like the bus topology, a ring has a single backbone cable. The ends of the backbone cable are joined to form a continuous ring.

Figure 2-6: Token Ring and FDDI Ring Topologies

Ring topologies almost always use an access method called token passing.

The token, a special signal, is passed from one station to the next. When it receives the token, a station can transmit on the network; other stations must wait.

 token passing

A network access method in which a token is passed from node to node on the network. A station which receives an empty token may transmit its data over the network.

 token

A special frame that circulates around a network, indicating the network’s availability for transmitting data.



The token ring that has become incorporated as a standard under IEEE 802.5 is normally implemented on twisted pair cable. Fiber Distributed Data

Interface (FDDI) is another standard (IEEE 802.8) that uses a ring topology and token passing and is implemented on fiber optic cable.

 token ring

An IEEE 802.5 access method that uses token passing on a logical ring network.

 Fiber Distributed Data Interface (FDDI)

FDDI (IEEE 802.8). A local area network standard that provides 100-

Mbps speeds over an optical fiber dual ring.

A 16-Mbps token ring requires shielded twisted pair cabling. All 4-Mbps token rings operate over shielded or unshielded pairs. Information is passed along the ring from one station to the next. Token ring topologies, with the exception of

FDDI, generally transmit in one direction only. Each station in turn acts as a repeater, regenerating the message until it reaches its destination.

Figure 2-7: Token Ring Topology

Many rings use a hub or media access unit or multistation access unit (MAU) in a central location, giving the appearance of a star. This “physical star,” however, still functions logically as a ring because the MAU completes the ring internally.

 multistation access unit (MAU)

Token ring hub. The ring size can be expanded by connecting multiple

MAUs. Also known as a media access unit.



Unlike bus topologies, ring topologies allow new stations to be added easily. The

MAU may be linked, creating a larger ring, up to the maximum number supported nodes. For example, one MAU might serve only to connect other rings.

Advantages of Ring Topologies

Figure 2-8: Advantages of Ring Topology

Network management:

• Faulty devices can usually be unplugged from the network without bringing the network down.

Product availability:

• An IEEE standard (802.5) token ring is well supported. Many hardware and software tools for network operation and monitoring are available.

Cost:

• Twisted pair cabling is relatively inexpensive and readily available.

Installation costs are relatively low.



Disadvantages of Ring Topologies

2-11

Figure 2-9: Disadvantages of Ring Topology

MAU expense:

• When supporting token ring, MAUs are generally more expensive than other connection devices.

Performance:

• With the exception of FDDI, ring standards are slower than other, more current, communication standards.

Cable expense:

• Some ring implementations require expensive specialty cables.

Tree Topologies

The tree topology can be thought of as several linked bus topologies, with one bus serving as the backbone. The other bus topologies are linked to the backbone by devices designed to link buses.



Figure 2-10: Tree Topology

Although the tree topology is a variation of the bus topology and similar cabling is used, there are some special advantages and disadvantages.

True tree topology implementations are seldom seen except in established networks. Even then, they are usually part of a hybrid network , integrated with newer technologies.

 hybrid network

A network that implements multiple topologies. For example, a hybrid network might combine tree and star topologies.

Advantages of Tree Topologies

Figure 2-11: Advantage of Tree Topology



Support of broadband transmission:

• Trees are often used for broadband transmission (which includes video transmission).

Disadvantages of Tree Topologies

2-13

Figure 2-12: Disadvantages of Tree Topology

Difficult troubleshooting:

• The troubleshooting and management problems of a single bus are magnified with the tree.

High cost:

• Network interface devices required for broadband transmission are costly.

Star Topologies

The star topology is similar to early terminal-to-host topologies. In the traditional star topology model, a central processor or central hub serves as a concentrator ; all data flows through this processor or hub from one station to another. The central processor is used in traditional logical star topologies, which are uncommon in non-mainframe environments.

 concentrator

A central site for network cable management.



Figure 2-13: Star Topology

Logical star topologies have become relatively uncommon with the success of bus and ring topologies. It is important not to confuse the logical star topology model with the physical star topology. Physical stars use central hubs or switches as connection devices. Although some less expensive hubs act as simple concentrators, most hubs and switches have additional features built in.

The physical star topology is currently the most popular choice in network implementations or upgrades.

 hub

Physical star concentrator. Passive hubs are unpowered hubs that act as concentrators only. Active hubs are powered hubs that may provide additional functionality.

 switch

A mechanical, electrical, or electronic device that opens or closes circuits, completes or breaks an electrical path, or selects paths or circuits. They operate on either a time- or space-division basis.

IEEE standards specify how ethernet signals can be sent over unshielded twisted pair (UTP) wire. With 10BaseT and 100BaseT , ethernet networks are connected via a physical star topology, centralizing all wiring in a single hub.

However, the 10BaseT configuration is still a logical bus using the CSMA/CD access method.

 unshielded twisted pair (UTP)

UTP. Twisted pair wiring that does not have a shield against electromagnetic interference (EMI) and radio frequency interference (RFI).

 10BaseT

An 802.3 standard for 10-Mbps data rates using twisted pair media and a physical star topology.



 100BaseT

An 802.3 standard for 100-Mbps data rates using twisted pair media and a physical star topology.

Advantages of Star Topologies

Figure 2-14: Advantages of Star Topology

Efficient troubleshooting:

• Managing and troubleshooting in a physical star is far simpler than in a bus.

When a fault occurs in a bus-based network, the manager may have to inspect kilometers of cable. In a centralized network, each station is attached to the hub with its own unshared cable. Key network resources are also centralized. With a star topology, the network administrator can usually go to a single location to begin troubleshooting.

Network control:

• More powerful control features can be easily implemented in the star topology. Intelligent hubs and switches can manage network traffic control directly, and can often adjust automatically for changing network requirements.

Limited failure:

• As each station is connected to the concentrator with its own cable, failure on one cable does not affect the rest of the network. Like the bus, this topology provides greater assurance of continuous operation of the network.



Familiar technology:

• Again, like the bus topology, equipment is cost-effective and can be purchased off the shelf from many vendors.

Easily expandable:

• Additional stations can be added to open ports on the hub. Hubs can be linked to increase the number of available ports.

Figure 2-15: Linked Hubs in Star Topologies

Cost effective:

• Most star topology networks use relatively inexpensive twisted pair cable. As star topology networks have become more popular, costs have steadily declined for components such as hubs and switches.

High data speeds:

• Current star topology implementations support a bandwidth of 100 Mbps or higher. Ethernet 100BaseT is one of the most common star topology networks.



Disadvantages of Star Topologies

2-17

Figure 2-16: Disadvantages of Star Topology

Central point of failure:

• If the central hub or switch goes down, all nodes connected to that hub will be unable to communicate.

Cable:

• The cabling required for most star topology implementations is relatively inexpensive, but a significant amount of cable may be required. Cable routing can become a problem in some buildings.


2-18

Mesh Topology

Local Area Networks (LANs)

Figure 2-17: Mesh Topology

As its name implies, mesh topology is a highly interconnected network with multiple redundant communication paths. The Internet is an example of a mesh topology network.

Mesh topology is most often used in WAN implementations where communication failures are a critical concern. It is rarely possible to justify the added hardware expense and management overhead for a LAN.



Advantages of a Mesh Topology

2-19

Figure 2-18: Advantage of Mesh Topology

High reliability:

• Because a mesh network is based on multiple communication paths, the network can compensate for the failure of a single route by routing traffic over an alternate path.

Disadvantages of a Mesh Topology

Figure 2-19: Disadvantages of Mesh Topology



Cost:

• A mesh topology requires a larger number of connection devices, typically routers, and more transmission media than other topologies.

Management:

• Mesh topology networks tend to be very large and can be difficult to manage and maintain. Unless carefully monitored, communication link failure may go, for a time, undetected.

Wireless (Cell) Topology

Figure 2-20: Wireless Topology

Wireless (or cell) topology is a radio frequency broadcast-based topology. The most common implementation in use at this time is based on the IEEE 802.11b standard. A wireless topology can be designed to allow nodes to communicate directly with one another or can route communication through a central access point . A wireless topology can be used as a stand-alone network or may be part of a hybrid network combined wired and wireless topologies.



Figure 2-21: Wireless Topology Access Point

 access point

A wireless network receiver/transmitter. It is most often used to connect wireless nodes to a traditional wired network.

Common wireless topologies support two networking modes: ad hoc and infrastructure. Ad hoc mode allows nodes to communicate directly with each other without any need for an access point. In infrastructure mode, all nodes communicate through an access point.

Advantages of Wireless Topologies

Figure 2-22: Advantages of Wireless Topology



Flexibility and portability:

• Wireless topology makes it possible for portable nodes, such as laptop computers, to remain in contact with the network without a physical connection to the network. Nodes can be relocated without making any wiring changes.

Reliability (ad hoc):

• An ad hoc network has no central point of failure with each station acting as receiver and transmitter with the ability to forward transmissions to other nodes.

Ease of implementation:

• Wireless topologies are relatively easy to install and maintain. One of the biggest advantages in installation is that no physical cabling is required, making it possible to implement network nodes in locations where it is impossible to run traditional wired networks.

Disadvantages of Wireless Topologies

Figure 2-23: Disadvantages of Wireless Topology

Limited bandwidth:

• Current wireless topologies operate at significantly lower bandwidths than other popular topologies, typically 2 Mbps or less.

Nonstandard implementations:

• Some manufacturers do not adhere closely to the published standards for wireless networks. Others have chosen to implement nonstandard solutions that are incompatible with other manufacturers' products.



Hybrid Topologies

2-23

Figure 2-24: Hybrid Topology

A hybrid topology is a topology implementing two or more standard topology types. A popular hybrid topology mixes star and wireless topology-based ethernet in the same network. The advantages and disadvantages of a hybrid topology will be the same as those of the topologies used. In addition, the mix of technologies may make the network more difficult to manage and maintain.



Lesson Summary

Application project

Consider the following situations. Which topology would be the most beneficial for each situation, and why? Be sure to consider distance limitations, network traffic, cost and existing technologies. a. A network with steady, moderate traffic in a limited geographical area b. A network that has frequent large bursts of traffic c. A network that is spread over a large geographical area with few nodes d. A network with several hundred nodes in a concentrated area e. A network of several LANs with frequent traffic between them f. A network that transmits a large number of delay-sensitive voice and video calls g. A network with a steady traffic flow that currently uses ethernet h. A network located in a building with no available routes for cable installation

Skills review

• The topology, or layout, is the way all components of the LAN are physically linked. Common topologies include bus, ring, tree, star, mesh, and wireless.

A hybrid topology may also be used, which is a combination of common topologies in a single network. A hub is a LAN component that creates a center for cable and network management.

• The standard bus configuration is simple: All stations are connected via a single backbone cable, called a bus. The most common access method for bus topologies is carrier sense multiple access (CSMA). Collision detection

(CD) and collision avoidance (CA) are alternative ways of handling the problems that occur when two nodes send messages simultaneously.

• Like the bus topology, a ring has a single backbone cable. The ends of the backbone cable are joined to form a continuous ring. Ring topologies almost always use an access method called token passing .

Fiber Distributed Data

Interface (FDDI) is a standard (IEEE 802.8) that uses a ring topology and token passing.

• The tree topology can be thought of as several linked bus topologies, with one bus serving as the backbone. The other bus topologies are linked to the backbone by devices designed to link buses.

• The star topology is similar to early terminal-to-host topologies. In the traditional star topology model, a central processor or central hub serves as a concentrator; all data flows through this processor or hub from one station to another. The central processor is used in traditional logical star topologies, which are uncommon in non-mainframe environments.



• Physical stars use central hubs or switches as connection devices. Although some less expensive hubs act as simple concentrators, most hubs and switches have additional features built in. The physical star topology is current the most popular choice in network implementations or upgrades.

• A mesh topology is exactly what its name implies, a highly interconnected network with multiple redundant communication paths. The Internet is an example of a mesh topology network. Mesh topology is most often used in

WAN implementations where communication failures are a critical concern.

It is rarely possible to justify the added hardware expense and management overhead for a LAN.

• Wireless or cell topology is a radio frequency broadcast-based topology. A wireless topology can be designed to allow nodes to communicate directly with one another or can route communication through a central access point. A wireless topology can be used as a stand-alone network or may be part of a hybrid network combining wired and wireless topologies.

• A hybrid topology is a topology implementing two or more standard topology types. The advantages and disadvantages of a hybrid topology will be the same as those of the topologies used. In addition, the mix of technologies may make the network more difficult to manage and maintain.

Now that you have completed this lesson, you should be able to:

Identify LAN topologies.

Describe the features and functions of bus topologies.

Describe the features and functions of ring topologies.

Describe the features and functions of tree topologies.

Describe the features and functions of star topologies.

Describe the features and functions of mesh topologies.

Describe the features and functions of wireless (cell) topologies.

Describe the identifying characteristic of a hybrid topology.



Lesson 2 Review

1. What are two ways bus topology responds when two messages are sent simultaneously?

__________________________________________________________________________

__________________________________________________________________________

2. What are advantages of the bus topology?

__________________________________________________________________________

__________________________________________________________________________

3. True or false: Whether physical stars or physical rings, ring topologies all act logically as rings.

_______________

4. Which topology would you use when unable to install network cable?

__________________________________________________________________________

__________________________________________________________________________

5. What is inherent in mesh topologies that enables them to provide high reliability?

__________________________________________________________________________

__________________________________________________________________________

6. What are advantages of star topologies?

__________________________________________________________________________

__________________________________________________________________________

7. Compare the two modes supported by wireless topologies.

__________________________________________________________________________

__________________________________________________________________________


Local Area Networks (LANs)

Local Area Networks

(LANs):

Academic Student Guide

Published by ComputerPREP

, Inc.

Phoenix, Arizona

Local Area Networks (LANs)

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Editors

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TRADEMARKS

DISCLAIMER

COPYRIGHT NOTICE

Table of Contents

List of Figures

Course Description

Topics Covered

ComputerPREP Courseware

Course Objectives

Classroom Setup

BJECTIVES

Lesson 1:

Overview

Pre-Assessment Questions

Introduction

Local Area Networks

LAN Advantages

LAN Elements

—

LAN Users

The LAN Market

Lesson Summary

Application project

Skills review

Now that you have completed this lesson, you should be able to:

Lesson 1 Review

BJECTIVES

Lesson 2:

Topologies

Pre-Assessment Questions

Introduction

Bus Topologies

Advantages of Bus Topologies

Disadvantages of Bus Topologies

Ring Topologies

Advantages of Ring Topologies

Disadvantages of Ring Topologies

Tree Topologies

Advantages of Tree Topologies

Disadvantages of Tree Topologies

Star Topologies

Advantages of Star Topologies

Disadvantages of Star Topologies

Mesh Topology

Advantages of a Mesh Topology

Disadvantages of a Mesh Topology

Wireless (Cell) Topology

Advantages of Wireless Topologies

Disadvantages of Wireless Topologies

Hybrid Topologies

Lesson Summary

Application project

Skills review

Now that you have completed this lesson, you should be able to:

Lesson 2 Review

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