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    Understanding NetworkingFundamentals

    M3100-002February 2000

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    Understanding NetworkingFundamentalsM3100-002February 2000

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    Copyright Information

    Copyright 1999, 2000Global Knowledge Network, Inc.

    The following publication, Understanding Networking Fundamentals, was developed by LANWorks, Inc. in

    cooperation with Global Knowledge Network, Inc. All rights reserved. No part of this publication may be

    reproduced or distributed in any form or by any means without the prior written permission of the copyright

    holder.

    This courseware may contain licensed images from the following sources: Corel Corporation, Corel Gallery;

    Broderbund Company, ClickArt 200,000; Nova Development Corporation, Art Explosion 125,000.

    Products and company names are the trademarks, registered trademarks, and service marks of their respective

    owners. Throughout this manual, Global Knowledge Network has used its best efforts to distinguish propri-

    etary trademarks from descriptive names by following the capitalization styles used by the manufacturer.

    Project Team

    MATTHEW FEENEY Course Director

    RHONDA HARMON Director, Content Development/Quality Assurance

    DAVID MANTICA Product Manager

    ART & PRODUCTION EDITORIAL

    SUSANNE GRADY Design Manager DAVID PRICE Standards Manager

    KATHY COINER Desktop Publisher MARK ATKINS Technical Editor

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    9000 Regency Parkway

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    Phone:919-461-8600

    Fax:919-461-8646http://am.globalknowledge.com

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    Understanding Networking Fundamentals v

    Global Knowledge Network, Inc.

    Career Track

    We invite you to call us at 919-461-8600 for assistance in selecting other courses in this

    curriculum track to meet your specific career/certification objectives.

    Understanding Networking Fundamentals is a good starting point for TCP/IP Network

    Analyst Certification, Web Technician Certification, and Cisco Career Certifications.

    Understanding NetworkingFundamentals

    Internetworking

    Routers andSwitches

    Internetworkingwith TCP/IP

    Introduction to

    WANTechnologies

    Network CablingSystems

    Network SecurityAdministration

    TroubleshootingTCP/IP Networks

    IP AddressManagement

    Virtual PrivateNetworks

    NetworkManagement

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    vi Understanding Networking Fundamentals

    Global Knowledge Network, Inc.

    Course Description

    In todays business world, timely information is the key to success. Meeting thechallenges of networking local area, wide area, and remote networks requires a firm

    understanding of data communications standards and emerging LAN/WAN internet-

    working technologies.

    This comprehensive course will help you understand networking terminology, technol-

    ogies, and how data moves in a real-world network environment. Beginning with the

    basics of data communications, you will learn data packet structure, frames, communi-

    cation architectures, transmission methods, DCE/DTE interfaces, modulation, andmultiplexing. You will build a LAN that demonstrates topologies, components, media

    access control methods, protocols, bit rates, and bandwidth in the classroom.

    Prerequisites

    We recommend, but do not require, a basic understanding of networking concepts.

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    Understanding Networking Fundamentals vii

    Global Knowledge Network, Inc.

    Font Conventions

    Different fonts and font styles signify different items or tasks. The following is a key to

    font usage.

    Font Item or Task Example

    Bold

    Commands, directory paths, file

    names, Web and e-mail addresses,registry keys, icons, and anything

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    or when programming

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    YesNoDialog is a subclass of Object, notDialog.

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    Global Knowledge Type user in the File box.

    $ SHOW CLUSTER /CONTINUOUS

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    viii Understanding Networking Fundamentals

    Global Knowledge Network, Inc.

    Welcome!

    I am pleased that you have selected Global Knowledge for your training needs. At Global

    Knowledge we strive to support all of the learning styles required by our students toachieve success as technical professionals.

    As the worlds largest IT training company, Global Knowledge is a respected and

    recognized multinational, independent IT education integrator. Whether you choose to

    learn through instructor-led training, written word, computer-based training, or Web

    delivery, Global Knowledge is committed to providing you the very best service and

    quality in each of these categories.

    For those of you who know Global Knowledge, or those of you who have just found us for

    the first time, our goal is to be your lifelong competency partner.

    Thank you again for the opportunity to serve you. We hope that you will think of us first

    when considering your future educational needs.

    Warmest regards,

    Duncan Anderson

    President and Chief Executive Officer

    Global Knowledge Network, Inc.

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    Understanding Networking Fundamentals TOC-1

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    Table of Contents

    1 Networking Overview

    Section Topics ...................................................................................................1-1

    Section Objectives .............................................................................................1-2

    What Is Computer Networking? .........................................................................1-3

    Network Segmentation and Connectivity ...........................................................1-4

    The Bandwidth Dilemma ...................................................................................1-5

    Network Components ........................................................................................1-6

    Network Design Issues ......................................................................................1-7

    Network Types ...................................................................................................1-8

    LANs ..................................................................................................................1-9

    Building Backbone ...........................................................................................1-11

    Campus Backbone ..........................................................................................1-13

    WANs ..............................................................................................................1-15

    MANs ...............................................................................................................1-16

    Enterprise Networks ........................................................................................1-17

    Networking Applications ..................................................................................1-18

    Networking Protocols .......................................................................................1-19

    Protocol Overview .....................................................................................1-20Speed vs. Reliability in a Network ...................................................................1-21

    Mainframe Environment ..................................................................................1-22

    Transmission Formats .....................................................................................1-23

    Asynchronous Character Format ..............................................................1-23

    Synchronous Frame Format .....................................................................1-23

    Transmission Methods ....................................................................................1-24

    Analog Signals ..........................................................................................1-24

    Digital Signals ...........................................................................................1-25

    2 Standards Organizations and the OSI Model

    Section Topics ...................................................................................................2-1

    Section Objectives .............................................................................................2-2Standards Organizations ...................................................................................2-3

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    IEEE and ANSI Standards .................................................................................2-5

    OSI Model ..........................................................................................................2-6

    OSI Network Communication ............................................................................2-7

    Layer 1 Physical Layer ..................................................................................2-9

    Physical Layer Connectivity Devices ........................................................2-10

    Layer 2 Data Link Layer ..............................................................................2-11

    IEEE 802.2 LLC ........................................................................................2-12

    Layer 3 Network Layer ................................................................................2-13

    Layer 4 Transport Layer ..............................................................................2-15Connection-Oriented Protocols .................................................................2-16

    Connectionless Protocols ..........................................................................2-17

    Layer 5 Session Layer ................................................................................2-18

    Layer 6 Presentation Layer .........................................................................2-19

    Layer 7 Application Layer ...........................................................................2-20

    Comparing the OSI Model to Real-World Networking .....................................2-21

    3 LAN Components

    Section Topics ...................................................................................................3-1

    Section Objectives .............................................................................................3-2

    LAN Overview ....................................................................................................3-3

    Main Components of a LAN ..............................................................................3-4Workstation Requirements ..........................................................................3-5

    Local Operating Systems ............................................................................3-6

    Networked Applications ...............................................................................3-7

    Network Interface Cards .............................................................................3-8

    NIC Drivers ..................................................................................................3-9

    Network Cabling Systems ...............................................................................3-10

    Category 5 UTP Horizontal Cabling ..........................................................3-11

    Category 5 UTP Installation ......................................................................3-12

    Fiber Optic Cable ......................................................................................3-13

    Fiber Optic Backbone Cabling ..................................................................3-14

    Connectivity Devices .......................................................................................3-15

    Concentrators, Hubs, and Repeaters ........................................................3-15

    Bridges ......................................................................................................3-16

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    Understanding Networking Fundamentals TOC-3

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    Switches ....................................................................................................3-18

    Routers ......................................................................................................3-19

    Network Operating Systems ............................................................................3-20

    Network Documentation ..................................................................................3-21

    Protocol Analyzers ...........................................................................................3-22

    LAN Baselining ................................................................................................3-23

    4 CSMA/CD Overview

    Section Topics ...................................................................................................4-1

    Section Objectives .............................................................................................4-2

    Ethernet Overview .............................................................................................4-3

    IEEE 802.3 CSMA/CD Protocol .........................................................................4-4

    Ethernet Collision Detection ..............................................................................4-5

    Ethernet Frame Formats ...................................................................................4-6

    Ethernet II Frame Format ............................................................................4-7Ethernet II Frame Format Example .............................................................4-9

    IEEE 802.3 with 802.2 Frame Format .......................................................4-10

    Ethernet Cabling Options ................................................................................4-11

    10Base5 Ethernet ............................................................................................4-12

    10Base2 Ethernet ............................................................................................4-13

    10BaseT Ethernet ............................................................................................4-14

    Ethernet Repeaters/Hubs/Concentrators ..................................................4-15

    Ethernet Transceivers ...............................................................................4-16

    10BaseFL ........................................................................................................4-17

    10 Mbps Ethernet Design ................................................................................4-18

    The 5-4-3 Rule ..........................................................................................4-18

    100 Mbps Ethernet Design ..............................................................................4-19

    Fast Ethernet 2-1 Rule ..............................................................................4-19100BaseTX ...............................................................................................4-20

    100BaseT4 ................................................................................................4-21

    100BaseFX 100 Mbps Ethernet Building Backbone .............................4-22

    Gigabit Ethernet ...............................................................................................4-23

    Ethernet Traffic Characteristics .......................................................................4-24

    Ethernet Errors ..........................................................................................4-25

    10/100 Mbps Ethernet Switching .....................................................................4-26

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    5 Network Operating Systems

    Section Topics ...................................................................................................5-1

    Section Objectives .............................................................................................5-2

    NOS Overview ...................................................................................................5-3

    The Client/Server Concept ................................................................................5-4

    The Dedicated Client/Server Network Environment ....................................5-5

    The Peer-to-Peer Client/Server Network Environment ...............................5-6

    File Service ........................................................................................................5-7Print Service ......................................................................................................5-8

    Mail Service .......................................................................................................5-9

    Communications Service .................................................................................5-10

    Database Service ............................................................................................5-11

    Directory/Security Services .............................................................................5-12

    NOS Protocol Comparison ..............................................................................5-13

    Typical UNIX Protocol Structure ...............................................................5-14

    Novell NetWare Protocol Structure ...........................................................5-15

    Windows NT Protocol Structure ................................................................5-17

    AppleShare Protocol Structure ..................................................................5-18

    Other NOSs ...............................................................................................5-19

    6 TCP/IP Overview

    Section Topics ...................................................................................................6-1

    Section Objectives .............................................................................................6-2

    TCP/IP Overview ...............................................................................................6-3

    The TCP/IP Protocol Suite ................................................................................6-4

    Network Access Layer .......................................................................................6-5

    Internet Layer ....................................................................................................6-6

    The IP Version 4 Header .............................................................................6-7

    IP Addressing ..............................................................................................6-8

    Binary Numbers ..........................................................................................6-9

    Subnetting .......................................................................................................6-10

    Subnet Mask Overview .............................................................................6-11

    Class A Subnetting ....................................................................................6-12

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    Class B Subnetting ....................................................................................6-13

    Class C Subnetting ...................................................................................6-14

    Subnet Mask Examples ............................................................................6-15

    Subnetting Examples ................................................................................6-17

    Variable Length Subnetting .......................................................................6-20

    Variable Length Subnet Mask Example ....................................................6-21

    Default Gateway Overview ..............................................................................6-22

    IP Address Servers ..........................................................................................6-23

    The Ping Command .........................................................................................6-24ARP .................................................................................................................6-25

    ARP In Action ............................................................................................6-26

    IP Version 6 .....................................................................................................6-28

    Host-to-Host Layer ..........................................................................................6-29

    TCP/IP Ports .............................................................................................6-30

    The TCP Header .......................................................................................6-31

    The UDP Header .......................................................................................6-32

    Process Layer Applications .........................................................................6-33

    FTP and TFTP ..........................................................................................6-34

    Telnet ........................................................................................................6-35

    E-mail ........................................................................................................6-36

    HTTP .........................................................................................................6-37

    DNS ...........................................................................................................6-38

    BootP ........................................................................................................6-40

    SNMP ........................................................................................................6-41

    7 Internetworking Overview

    Section Topics ...................................................................................................7-1

    Section Objectives .............................................................................................7-2

    Internetworking Overview ..................................................................................7-3

    Network Segmentation ......................................................................................7-4

    Networking Equipment ......................................................................................7-5

    Physical Segmentation ......................................................................................7-6

    Bridging and Switching ......................................................................................7-7

    Bridge and Switch Operation ......................................................................7-8

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    Bridge and Switch Types ............................................................................7-9

    Ethernet Switching ....................................................................................7-11

    Spanning Tree Algorithm ..........................................................................7-12

    Token Ring Switching ...............................................................................7-13

    FDDI Switching .........................................................................................7-14

    ATM Switching ..........................................................................................7-15

    Logical Segmentation ................................................................................7-16

    Routing Overview ............................................................................................7-17

    Routing IP .................................................................................................7-18Routing Protocols ......................................................................................7-19

    Routing Metrics .........................................................................................7-20

    Routing Protocol Operation .......................................................................7-21

    RIP ............................................................................................................7-22

    RIP Routing Tables ...................................................................................7-23

    RIP 1 Message Format .............................................................................7-24

    RIP 2 Message Format .............................................................................7-25

    OSPF ........................................................................................................7-26

    OSPF Messages .......................................................................................7-27

    IGRP .........................................................................................................7-28

    BGP ...........................................................................................................7-29

    Firewalls ..........................................................................................................7-30

    Firewall Types ...........................................................................................7-31

    8 WAN Components

    Section Topics ...................................................................................................8-1

    Section Objectives .............................................................................................8-2

    WAN Overview ..................................................................................................8-3

    Telecommunications Infrastructure ...................................................................8-4

    Connection Types PVC and SVC .................................................................8-5

    WAN Technologies ............................................................................................8-6

    WAN Circuit Switching ................................................................................8-7

    WAN Packet Switching ...............................................................................8-8

    Wide Area Transmission Rates ...................................................................8-9

    WAN Media Types and Physical Interfaces ....................................................8-10

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    Understanding Networking Fundamentals TOC-7

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    WAN Signaling Specifications ...................................................................8-11

    WAN Equipment ..............................................................................................8-12

    Modems ....................................................................................................8-13

    DSU/CSU ..................................................................................................8-14

    Multiplexing ......................................................................................................8-15

    Time Division Multiplexing .........................................................................8-16

    TDM Hierarchy ..........................................................................................8-17

    Multiplexing Example ................................................................................8-18

    SONET ............................................................................................................8-19Overview ...................................................................................................8-19

    SONET Specifications ...............................................................................8-20

    9 WAN Services

    Section Topics ...................................................................................................9-1

    Section Objectives .............................................................................................9-2WAN Access and Services ................................................................................9-3

    WAN Service Options .................................................................................9-4

    Leased Lines .....................................................................................................9-5

    DDS .............................................................................................................9-6

    T1 Service ...................................................................................................9-7

    Fractional T1 Service ..................................................................................9-8T3 and Fractional T3 ...................................................................................9-9

    Switched Lines ................................................................................................9-10

    POTS ........................................................................................................9-11

    ISDN Overview ..........................................................................................9-12

    ISDN BRI ...................................................................................................9-13

    ISDN PRI ...................................................................................................9-14

    SMDS ........................................................................................................9-15

    DSL ...........................................................................................................9-16

    Packet-Switching Networks .............................................................................9-17

    X.25 Overview ...........................................................................................9-18

    Frame Relay Overview ..............................................................................9-19

    Frame Relay Components ........................................................................9-20

    Frame Relay Operation .............................................................................9-21

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    Frame Relay Frame Format ......................................................................9-22

    Frame Relay CIR ......................................................................................9-23

    ATM ...........................................................................................................9-24

    ATM Implementations ...............................................................................9-25

    ATM Layers ...............................................................................................9-26

    ATM Service Classes ................................................................................9-27

    ATM Cell Structure ....................................................................................9-28

    ATM Virtual Paths and Channels ..............................................................9-29

    10 The Internet

    Section Topics .................................................................................................10-1

    Section Objectives ...........................................................................................10-2

    Internet Overview and Structure ......................................................................10-3

    Intranets ...........................................................................................................10-5

    Accessing the Internet .....................................................................................10-6Internet Applications and Tools .......................................................................10-7

    The World Wide Web ................................................................................10-8

    URL ...........................................................................................................10-9

    HTTP .......................................................................................................10-10

    Java .........................................................................................................10-11

    Networking Resources on the Internet ..........................................................10-12Future Internet Trends ...................................................................................10-13

    Appendix A: Token Passing Protocols

    Section Topics .................................................................................................. A-1

    Section Objectives ............................................................................................ A-2

    Token Passing Protocols Overview .................................................................. A-3Benefits of Token Passing Protocols ......................................................... A-4

    IEEE 802.5 Token Ring .................................................................................... A-5

    Token Ring Token Passing Protocol .......................................................... A-6

    Token Ring Design and Implementation .................................................... A-7

    Token Ring Physical and Logical Design ................................................... A-8

    Token Format ............................................................................................. A-9

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    Understanding Networking Fundamentals TOC-9

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    Token Ring Frame Format ....................................................................... A-10

    Token Ring Frame Example .................................................................... A-11

    Token Ring Active Monitor ....................................................................... A-13

    ANSI X3T9.5 FDDI ......................................................................................... A-14

    Campus Backbone Design Example ........................................................ A-15

    FDDI Token Passing Protocol .................................................................. A-16

    FDDI Dual Ring Topology ........................................................................ A-17

    FDDI Token Format ................................................................................. A-18

    FDDI Frame Format ................................................................................. A-19FDDI Frame Decode ................................................................................ A-20

    FDDI Port Types ...................................................................................... A-21

    FDDI Cabling Options .............................................................................. A-22

    Ethernet/Token Ring/FDDI Comparison ......................................................... A-23

    Appendix B: Section Review Answers

    Section 1: Networking Overview ................................................................ B-2

    Section 2: Standards Organizations and the OSI Model ............................ B-2

    Section 3: LAN Components ...................................................................... B-3

    Section 4: CSMA/CD Overview .................................................................. B-3

    Section 5: Network Operating Systems ..................................................... B-4

    Section 6: TCP/IP Overview ....................................................................... B-4Section 7: Internetworking Overview .......................................................... B-5

    Section 8: WAN Components .................................................................... B-5

    Section 9: WAN Services ........................................................................... B-6

    Section 10: The Internet ............................................................................. B-6

    Appendix A: Token Passing Protocols ....................................................... B-7

    Appendix C: Crossword Puzzle

    Networking Fundamentals Crossword Puzzle .................................................. C-2

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    Understanding Networking Fundamentals 1-1

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    1

    Networking Overview

    Section Topics

    Network Segmentation and Connectivity The Bandwidth Dilemma

    Network Components

    Network Design Issues

    Network Types

    Networking Applications

    Networking Protocols

    Speed vs. Reliability in a Network

    Mainframe Environment

    Transmission Formats

    Transmission Methods

    N t ki O i

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    1-2 Understanding Networking Fundamentals

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    Networking Overview

    Section Objectives

    After completing this section, you will be able to: Define computer networking

    Identify the key factors that influence how networks are designed

    List the basic components of a network

    Identify the various types of networks used today, including LANs, WANs, and

    MANs

    Define what a protocol is and what it is used for

    Describe analog and digital signaling

    Networking Overview

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    Understanding Networking Fundamentals 1-3

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    Networking Overview

    What Is Computer Networking?

    Figure 1: What Is Computer Networking?

    The term computer networking means different things to different people. But to most, it

    indicates a combination of hardware and software that provides a means for the various

    computers in an organization to communicate with one another.

    In todays business world, each computer network is designed to fit the needs of aparticular company. No two companies networking needs are exactly the same, and no

    two computer networks are exactly the same. Each network is continually changing with

    the addition of new devices, applications, and services. Old technology is being phased

    out and companies are upgrading at a fast pace.

    Users and people who support a computer network need to continually adapt to the

    technologies available in the market and in place at their company. In this class, we will

    discuss many common components and uses of computer networks. We will explore thevarious aspects of todays and tomorrows networking environment.

    FDDI

    ISDN

    TCP/IP

    CAT 5 UTP

    Modem ATM

    Router

    Ethernet

    Tokenring X.25

    FrameRel

    ay

    Netware

    Windows NT

    Hub

    Fiber opticsSwitch

    T1

    DSU/C

    SU

    Intranet

    Internet

    Bridge

    Networking Overview

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    Networking Overview

    Network Segmentation and Connectivity

    Figure 2: Network Segmentation and Connectivity

    There are many factors that influence the way that networks are designed. Some of the key

    factors include:

    The size of the network

    The performance of the network (user application requirements)

    The security of the network

    The manageability of the network

    The connectivity requirements

    The budget for the network

    For these and other reasons, we usually segment the networks into clusters of users and

    attempt to locate their resources as close to home as possible. To illustrate this point, a

    company with 200 users at its corporate headquarters would not install all users on the

    same LAN (local area network). This company would more likely segment the network

    into smaller departmental LANs, which could in turn be connected to one another.

    20

    2020

    20

    20

    20

    20

    20

    20

    20200

    Ten 20-user LANs200-user LAN(Not a good idea)

    Networking Overview

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    Understanding Networking Fundamentals 1-5

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    Networking Overview

    The Bandwidth Dilemma

    Figure 3: The Bandwidth Dilemma

    Important Term

    Bandwidthis the data transfer capacity of a communications system.

    Computer networks have a finite bandwidth. Just as a water pipe allows a finite amount

    of water to pass through the pipe, a network allows a finite amount of data to travel

    through it.

    Some of the factors that cause bandwidth shortage include:

    LANs that use a shared media access control protocol, such as Ethernet,

    token ring, and FDDI (Fiber Distributed Data Interface)

    An increase in user population

    An increase in application requirements

    An increase in end-station processing power

    A network engineer must keep many factors in mind when designing, installing,

    upgrading, or troubleshooting a computer network.

    Network

    Networking Overview

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    Networking Overview

    Network Components

    Figure 4: Basic Network Components

    The basic components of networks include:

    The end stations

    The applications being run on the end stations The network that will support the traffic between end stations

    A network that was designed five years ago to support basic networking applications may

    have difficulty supporting recently developed high-end applications (e.g., medical

    imaging and live video teleconferencing).

    Network designers and managers need to understand and monitor the types and frequency

    of networked applications.

    Real-World Application

    For example, a large bank planning to implement a bank-wide document imaging systemshould take steps to predict the impact of the additional traffic on the existing and new

    networks. With this information, proper component selection and deployment can be

    accomplished.

    End stations

    Applications

    NetworksLAN

    WAN

    MAN

    PCsWorkstations

    ServersPrinters

    E-mailFile transferImagingVideo

    RoutersHubs

    Switches

    Frame RelayEthernet

    Networking Overview

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    Understanding Networking Fundamentals 1-7

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    g

    Network Design Issues

    Figure 5: Network Design Issues

    Network design often requires input from many sources. Each organizations network has

    evolved through the years. Many organizations implement physical segmentation for

    performance reasons and provide logical segmentation for security and connectivity

    issues.

    Network Design Basics

    Physical Connectivity

    Physical connectivity for each network device is typically accomplished by using a hub/

    concentrator/repeater, cabling, and a NIC (network interface card) in a LAN environment.

    Physical Segmentation

    Physical segmentation is obtained by using bridges and switches that create separate

    collision domains in Ethernet and separate rings in token ring. This improves the perfor-mance of the network for attached devices by limiting traffic flow based on NIC or MAC

    (media access control) addresses.

    Logical Segmentation

    Logical segmentation is obtained using routers installed and configured to create and

    connect different networks and subnetworks. Traffic can be directed between subnets to

    meet connectivity and security requirements.

    User requirements

    Management goals

    Security concerns

    Performance issues

    Legacy systems

    Budget considerations

    Traffic patterns

    Protocols

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    Network Types

    Figure 6: Basic Network Types

    Computer network connections usually fall into one of the following categories:

    Figure 7: Basic Network Types

    For all practical purposes, most network connections are forms of LANs or WANs.

    Network Type Network Characteristics

    LAN (local area network) Connects users in a department, company, or group

    Building backbone Connects LANs together within a building

    Campus backbone Connects building LANs together

    MAN (metropolitan area network) Connects sites in and around a large city together

    WAN (wide area network) Connects sites around the country and the world together

    Enterprise network Connects many, or all of the above, types of networks

    Server

    User

    User

    WAN

    Router

    Building

    Backbone

    Sales

    LAN

    Hub

    AccountingLAN

    Server

    AdministrationLAN

    User

    User

    Server

    Hub

    Hub

    Connectivitydevice

    User

    User

    Other sites andnetworks

    Switch

    WAN LAN

    WAN LAN

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    LANs

    Figure 8: LANs

    Important Term

    A LAN (local area network) normally connects devices to each other and to resources at a

    departmental level within an organization.

    A LAN generally supports from 10 to 40 users and is often centered around one or more

    file servers. The LAN uses an NOS (network operating system), which is the software thatallows the devices to communicate with each other.

    A NIC is installed and configured for each device on the LAN. The devices on a LAN are

    typically connected together using a hub (repeater) and a category 5 UTP (unshielded

    twisted pair) cabling system. The LAN usually has a connection to the building backbone

    for access to other departmental LANs, MANs, and WANs.

    NOS clientsoftware

    Hub/repeater

    Patch panelPC

    Laptop

    Workstation

    Printer

    CD-ROM/WORM

    File/application/print server

    Router or switch

    To buildingbackbone

    Typical LANComponents

    NOS server

    software

    Category 5 UTPcable system

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    Examples of current LAN standards that provide this connectivity include:

    10BaseT Ethernet

    100BaseTX Ethernet

    16 Mbps token ring

    155 Mbps ATM (Asynchronous Transfer Mode)

    100 Mbps FDDI

    Gigabit Ethernet

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    Building Backbone

    Figure 9: Building Backbone

    Important Term

    A building backboneis a network connection that normally carries traffic between depart-

    mental LANs and an internetworking device such as a router or switch.

    A building backbone can also provide the connectivity to other networks such as campus

    backbones, MANs, or WANs.

    A building backbone usually consists of a fiber optic cable system that connects the

    electronic components (e.g., hubs, switches, bridges, and routers). It is usually a high-

    speed connection in order to support the high volume of traffic between LANs.

    LAN

    Router

    Hub

    Hub

    Hub

    LAN

    LAN

    To WAN,MAN, orcampus

    Building

    backbone

    Fiber optic

    cablesystem

    Patch cablesFiber opticpatch panel

    Users

    Users

    Users

    Cat5 UTP

    Switch

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    Campus Backbone

    Figure 10: Campus Backbone

    Important Term

    A campus backboneis a network connection used to carry traffic to and from LANs located

    in various buildings on a campus.

    A campus backbone is designed for sites that have a group of buildings at a single

    location. Examples of campuses include corporate headquarters, universities, airports, andresearch parks.

    A campus backbone is usually made up of multimode and/or single mode fiber optic cable

    installed between the buildings.

    The fiber optic cable is used to connect the internetworking devices, such as bridges,

    routers, and switches. The backbone is high speed in order to carry large volumes of traffic

    between sites.

    WAN

    Building 1Building 2

    Building 4

    Building 3

    Fiber opticcable

    LANs

    LANs

    LANs

    LANs

    Router/switch

    Router/switch

    Router/switch

    Router/switch

    In this diagram, the campus backbonecontains connections between therouters and switches on a campus.

    Networking Overview

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    Examples of campus backbones include:

    FDDI

    16 Mbps token ring

    155 Mbps and 622 Mbps ATM

    100BaseFX Ethernet

    Gigabit Ethernet

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    WANs

    Figure 11: WANs

    Important Term

    WANs (wide area networks) are networks that connect geographically dispersed sites.

    A WAN connects different cities, states, or countries. WANs are obtained through a

    service provider and normally come in the form of a leased line or circuit-switching

    technology. Often, the WAN connects routers in different locations. Speeds have histori-

    cally been low to medium (less than 1 Mbps). In recent years, however, speeds of 45 Mbps

    and more have been implemented by organizations.

    Examples of WANs include:

    56 Kbps circuit

    ISDN (integrated services digital network)

    T1 and T3 connections

    Frame relay

    X.25

    ATM

    Modems and regular telephone lines

    1st

    Tokyo

    New York

    London

    Chicago

    SeattleService

    providerWAN

    RouterRouter

    Router

    Router

    Router

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    MANs

    Figure 12: MANs (Metropolitan Area Networks)

    Important Terms

    A MAN (metropolitan area network)is a network designed to carry traffic between locations

    within a single metropolitan area.

    MANs are obtained through a service provider for a fixed monthly fee.

    The MAN connects routers and switches. The process of obtaining a MAN is similar to

    that of a WAN, except a MAN stays in one city or metropolitan area.Examples of MANs include:

    SMDS (Switched Multimegabit Data Service)

    FDDI

    ATM

    ServiceproviderMAN

    1st

    Manufacturing

    facility

    Research

    building

    Headquarters

    LANs

    LANs

    LAN

    Chicago metropolitanarea

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    Enterprise Networks

    Figure 13: Enterprise Network

    An enterprise network has many or all of the following components connected in a

    cohesive and managed fashion.

    Figure 14: Enterprise Network Components

    Component Usage

    LAN For each department or group

    Building backbone Ties together LANs in a building

    Campus backbone Connects buildings

    MAN Ties sites in a city together

    WAN Connects geographically dispersed locations

    CorporateWAN

    Dallascampus

    New YorkMAN

    Seattle

    Chicago

    LANs

    LANs LANs

    LANs

    LANs

    Router

    Router

    Router

    Router

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    Networking Applications

    Figure 15: Networking Applications

    The applications running on todays computer networks vary greatly from company to

    company. A network must be designed with the applications in mind.

    A general categorization of networking applications includes the following:

    Figure 16: Networking Applications

    Different applications affect how well a network performs. Each network has a finite

    bandwidth or capacity. Thus, network designers and engineers should be aware of the kind

    and frequency of the traffic traversing the networks.

    Application Examples

    Standard office applications E-mail, file transfers, printing

    High-end office applications Imaging, CAD, software development

    Manufacturing automation Process control

    Mainframe connectivity Personal computer and terminal support

    Multimedia applications Live interactive video

    High-end officeapplications

    Manufacturingautomation

    Mainframeconnectivity

    Multimedia

    applications

    Standard officeapplications

    Network

    Device

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    Networking Protocols

    Figure 17: Networking Protocols

    Computer networks use protocols to communicate. These protocols define the procedures

    that the systems involved in the communications process will use. Many protocols are

    used today to provide networking capabilities. Often, protocols are combined into a

    communication architecture orprotocol stack.

    Important Term

    Protocol A set of rules allowing communication between computers for the exchange of

    information.

    Each protocol in the communication architecture provides for a function needed to make

    the networking possible. Multiple protocols are used so that the job can be broken up into

    manageable pieces. Each module that implements a protocol can be developed and

    updated independently of other modules as long as the interface between modules remains

    constant.

    T How much data can I send?

    T How shall I send it?

    T

    How shall I address it?

    T

    How will I check for errors?

    Network

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    Protocol Overview

    Protocols used in networks usually fall into one of the following groups:

    Figure 18: Protocol Overview

    These protocols collectively supply the details that allow computers around the world to

    communicate with each other.

    LANThese protocols define how datatraverses LANs. Issues such as framestructure, media access, and physicalrequirements are detailed.

    Ethernet Token ring FDDI ATM

    WANThese protocols define how data movesbetween distant locations.

    Frame relay X.25 ATM ISDN

    Networkingsoftware

    NOS software provides logicalconnections and application support forthe user and devices.

    TCP/IP Windows NT Novell

    NetWare

    RoutingThese protocols assist in connectingmultiple networks and transporting databetween these networks.

    RIP OSPF IGRP

    LANThese protocols define how datatraverses LANs. Issues such as framestructure, media access, and physicalrequirements are detailed.

    Ethernet Token ring FDDI ATM

    WANThese protocols define how data movesbetween distant locations.

    Frame relay X.25 ATM ISDN

    Networkingsoftware

    NOS software provides logicalconnections and application support forthe user and devices.

    TCP/IP Windows NT Novell

    NetWare

    RoutingThese protocols assist in connectingmultiple networks and transporting databetween these networks.

    RIP OSPF IGRP

    Protocol Group Description Example

    Networking Overview

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    Speed vs. Reliability in a Network

    Figure 19: Speed vs. Reliability in a Network

    There are many factors involved in designing a computer network. Some of these factors

    include:

    Goals of the network as defined by the management of the organization

    Security of the data on the network

    Up-time requirements of the network

    Response-time requirements for the network

    Cost of the network and its resources

    The main balancing act in networking is finding the right mix of speed and reliability.

    Often, the performance of a network is slowed down by error checking, encryption, and

    acknowledgments. However, in many organizations, they are required, and are therefore

    incorporated into the protocols.Some networking protocols are very reliable and require a significant amount of overhead

    to provide this level of service. These protocols are referred to as connection-oriented

    protocols. Other protocols are designed with speed in mind and forego some of the

    reliability features of the connection-oriented protocols. These quick protocols are

    referred to as connectionless protocols.

    Speed Reliability

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    Mainframe Environment

    Figure 20: Mainframe Environment

    There are several different mainframe environments in use today. Connectivity options

    vary depending on the mainframe vendor, model, and connectivity strategy. Three

    mainframe connectivity options are shown in Figure 20:

    Traditional SNA (Systems Network Architecture) environment

    Software emulation for LAN-attached PCs

    SNA/LAN peripheral gateway

    MainframeConnectivity Options

    Mainframe

    FEP(front-endprocessor)

    Mainframe/

    LAN/gateway

    Router

    Router

    Clustercontrollers

    Dumbterminals

    LAN-attached PCwith mainframe

    emulation software

    LAN-attached

    PC

    Hubs

    Hub

    Traditional SNA

    Communicationscontroller

    1

    3

    2

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    Transmission Formats

    Data on computer networks can be sent two ways:

    One character at a time (asynchronous)

    In groups of characters (synchronous)

    Asynchronous Character Format

    Figure 21: Asynchronous Character Format

    Asynchronous character format is a transmission method in which single bytes of data aresent serially onto a network. It is a simple and inexpensive method of sending and

    receiving data. An implementation example would be a modem connection.

    Synchronous Frame Format

    Figure 22: Synchronous Character Format

    Synchronous frame format is a transmission method in which large portions of data aresent on a network. This is calledframe transmission. The frame usually contains

    addressing, a variable-sized data field, and error checking. An implementation example

    would be an Ethernet LAN.

    Start1 bit

    Character8 bits

    Parity1 bit

    Stop1 bit

    Control fieldSource address

    Destination address

    Data fieldVariable size

    (large amount of data)

    ErrorChecking

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    Transmission Methods

    Analog Signals

    Figure 23: Analog Signals

    Analog signals move down wires as electromagnetic waves. The speed of these waves

    indicates the frequency, stated in hertz. When the telephone was invented in 1876, it used

    analog signals to carry voice traffic. A problem with analog transmission is that, as the

    signals travel over a wire, they get weaker and pick up electrical noise from power lines

    and other sources. The weakened signals need to be amplified, but the amplifier is unable

    to tell good electrical energy from bad. Therefore, the noise is repeated as well. Today,most of the public telephone network is digital. However, analog services, such as POTS

    (plain old telephone service), are still common.

    Figure 24: Analog Frequency Measurements

    Abbreviation Name Description

    Hz Hertz Complete wave cycles per second

    kHz Kilohertz Thousands of complete wave cycles per secondMHz Megahertz Millions of complete wave cycles per second

    GHz Gigahertz Billions of complete wave cycles per second

    TimeAmplitude

    Period(frequency)

    Phase change

    Wave propagation direction

    Networking Overview

    Di it l Si l

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    Digital Signals

    Figure 25: Digital Signals

    Digital transmission is signal transmission over wires, fiber optics, or through the air

    where a digital encoding technique is used to transmit binary bits (1s and 0s) through the

    medium. The benefit of this technique is that, as the signal passes through devices (e.g.,

    repeaters, routers, switches), the digital signal is sampled and retransmitted as a full, clean,

    new signal. Examples of digital encoding schemes include Manchester Encoding for

    Ethernet and AMI (alternate mark inversion) in T1 lines.Digital signaling has the following advantages over analog signaling:

    Higher speeds

    Fewer errors

    Clearer voice quality

    Figure 26: Digital Frequency Measurements

    Abbreviation Name Description

    Kbps Kilobits Thousands of bits per second

    Mbps Megabits Millions of bits per second

    Gbps Gigabits Billions of bits per second

    Tbps Terabits Trillions of bits per second

    1 1 1 1

    000

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    Knowledge

    Checkpoint

    Section Review

    1. Networks are physically and logically segmented in order to achieve performance andsecurity goals.

    a. True

    b. False

    2. This network type is used to connect users in a department, group, or company.

    3. Networking applications used on a network, such as e-mail and imaging, have no impact

    on how the network should be designed.

    a. True

    b. False

    4. This network type is used to connect distant locations and is obtained through a serviceprovider.

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    2

    Standards Organizationsand the OSI Model

    Section Topics Standards Organizations

    IEEE and ANSI Standards

    OSI Model

    OSI Network Communication

    OSI Layers

    Comparing the OSI Model to Real-World Networking

    Standards Organizations and the OSI Model

    Section Objectives

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    Section Objectives

    After completing this section, you will be able to:

    Recognize the relevant network standards used in todays networks

    Identify each layer of the OSI model

    Describe how the OSI model is used today for comparison and educational

    purposes

    Standards Organizations and the OSI Model

    Standards Organizations

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    Standards Organizations

    Figure 27: Standards Organizations

    These organizations influence and add to the networking specifications available today.

    Figure 28: Standards Organizations

    Acronym Name of Organization

    ANSI American National Standards Institute

    EIA Electronic Industries Association

    IAB Internet Architecture Board

    IEEE Institute of Electrical and Electronics Engineers

    IETF Internet Engineering Task ForceIRTF Internet Research Task Force

    ISO International Organization for Standardization

    ITU International Telecommunication Union, formerly CCITT (International Telegraph and

    Telephone Consultative Committee)

    TIA Telecommunications Industry Association

    ATM OtherFrame relay

    ITU IEEE

    EIA/TIA

    IETF IRTF

    IAB

    ISO

    Vendor Forums

    ANSI

    Standards Organizations and the OSI Model

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    Note

    Networking standards can be obtained from Global Engineering Documents:

    1-800-854-7179 (U.S. orders)

    303-397-7956 (international orders)

    Standards Organizations and the OSI Model

    IEEE and ANSI Standards

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    IEEE and ANSI Standards

    IEEE and ANSI normally work on local and metropolitan area committees and subcom-

    mittees, including those shown in the tables below.

    IEEE

    Figure 29: IEEE Committees and Subcommittees

    ANSI

    Figure 30: ANSI Committees and Subcommittees

    Committee Subcommittee Subtask

    802 802.1 High-level interface

    802.2 LLC sublayer802.3 CSMA/CD (Ethernet) networks

    802.3u 100 Mbps Ethernet

    802.3z Gigabit Ethernet

    802.4 Token bus networks (ARCnet)

    802.5 Token ring networks

    802.6 Metropolitan area networks (DQDB)802.7 Broadband technical advisory group

    802.8 Fiber optic technical advisory group

    802.9 Integrated voice and data LAN working group

    802.10 LAN security working group

    802.11 Wireless networking

    802.12 Demand priority access methods (100VG AnyLAN)802.14 Cable modems

    Committee Subcommittee Subtask

    X3 X3T9.5 FDDI standards

    Standards Organizations and the OSI Model

    OSI Model

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    Figure 31: OSI Model

    The OSI (Open Systems Interconnection) model was created by the ISO as a basis for

    communication systems. The seven layers of the model are set up so that each layer works

    independently of another and allows a modular change of protocols. This model is a

    foundation for comparing protocols; however, most protocols deviate from the rules set up

    by the OSI model.

    The OSI model is normally used for educational and comparative purposes with respect to

    products and technologies commercially available in todays networks.

    Physical

    Data link

    Network

    Transport

    Session

    Presentation

    ApplicationUser networking applications andinterface to the network

    Encoding language used intransmission

    Job management tracking

    Data tracking as it moves througha network

    Network addressing and packettransmission on the network

    Frame transmission across aphysical link (LAN or WAN)

    Transmission method of bits onthe network

    7

    6

    5

    4

    3

    21

    Layer FunctionName

    Standards Organizations and the OSI Model

    OSI Network Communication

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    Figure 32: OSI Network Communication

    Each layer implements a specific communications function. Each layer should be

    independent of all others. This independence provides for modular development and later

    enhancements or upgrades.

    Characteristics of network communications include:

    A header, created by each layer, implements the function for that layer.

    Important Term

    PDU (protocol data unit) The combination of header and data

    H2 H3 H4 H5 H6 H7 D T

    H2 H3 H4 H5 H6 H7 D T

    H3 H4 H5 H6 H7 D

    H4 H5 H6 H7 D

    H5 H6 H7 D

    H6 H7 D

    H7 D

    H2 H3 H4 H5 H6 H7 D T

    H2 H3 H4 H5 H6 H7 D T

    H3 H4 H5 H6 H7 D

    H4 H5 H6 H7 D

    H5 H6 H7 D

    H6 H7 D

    H7 D

    1

    2

    3

    4

    5

    6

    7

    1

    2

    3

    4

    5

    6

    7

    Frame

    Frame

    Packet or datagram

    Frame

    Frame

    Packet or datagram

    Application protocol

    Presentation protocol

    Session protocol

    Transport protocol

    Network protocol

    Data link protocol

    Physical protocol

    H2H3H4H5H6H7DT

    Host A Host B

    OSI layers

    D = Data H = HeaderT = Trailer

    Interconnecting media

    Sender Receiver

    Standards Organizations and the OSI Model

    The PDU created by one layer is passed as data to the PDU created by the next

    layer below For example the layer 3 PDU would contain H4 through H7 plus

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    layer below. For example, the layer 3 PDU would contain H4 through H7, plus

    the data, plus H3 information.

    The target device of the network communication processes data from the

    bottom of the OSI model up. The header is stripped off before being sent up to

    the next level.

    Standards Organizations and the OSI Model

    Layer 1 Physical Layer

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    Figure 33: Physical Layer

    The physical layer of the OSI model defines connector and interface specifications, as

    well as the medium (cable) requirements. Electrical, mechanical, functional, and

    procedural specifications are provided.

    Components of the physical layer include:

    Cabling system components

    Connector design and pin assignments

    Hub/repeater/concentrator specifications

    Wireless system components

    In a LAN (local area network) environment, category 5 UTP cable is generally used for

    the physical layer in individual device connections. Fiber optic cabling is often used for

    the physical layer in backbone connections. For example, fiber optics would typically be

    installed when connecting a hub on the twentieth floor of a building to a switch located inthe first-floor data center.

    Cat5 UTP

    Wall jack

    Patch panel

    Hub/repeater

    Device

    NIC

    Standards Organizations and the OSI Model

    Physical Layer Connectivity Devices

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    Figure 34: Physical Layer Connectivity Devices

    Characteristics

    Connectivity devices are used to connect devices on a LAN. Examples include

    10BaseT hub and token ring MAU (multistation access unit).

    The hub samples the incoming bit stream and repeats a good signal to the other

    devices connected to the hub.

    Ethernet, token ring, and FDDI (Fiber Distributed Data Interface) hubs operate

    differently. An Ethernet hub logically connects users into a bus (as shown in

    Figure 34.) Token ring and FDDI hubs logically connect stations into a ring.

    The hub does not look at data to see what the destination is. It only looks at bits

    as they come into the hub. For this reason, it is classified as a layer 1

    component.

    Connectivity devices, such as a 10BaseT hub, provide a convenient means to connectdevices to a LAN. Prior cabling systems, such as 10Base2 Ethernet, used coax cabling

    connected in a physical bus topology. This method was plagued by network downtime and

    difficulty in moving users.

    10BaseTEthernet hub

    10BaseTEthernet hub

    Fiber optics

    A B C D E F G

    1

    1

    0

    1

    1

    1

    0

    1

    1

    1

    0

    1

    1

    0

    1

    1

    1

    1

    0

    1

    1

    1

    0

    1

    1

    1

    0

    1

    1 1 0 1

    Standards Organizations and the OSI Model

    Layer 2 Data Link Layer

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    Figure 35: Data Link Layer

    LAN networking components that operate at the data link layer include bridges, switches,

    and NICs (network interface cards).

    The data link layer accomplishes the following functions:

    Builds and sends frames (containing the NOS (network operating system)

    information plus user data) out to a network

    Destination and source MAC (media access control) address fields (NIC

    addresses) Error detection fields

    Synchronization field

    A field which specifies the network layer protocol being implemented

    On the sender side, the NIC passes the frame to the physical layer, which transmits the

    data to a physical link. On the receiver side, the NIC processes bits from the physical layer

    and processes the message based on its contents.

    Ethernet switch

    Hub

    Frame

    Fram

    e

    Hub

    10BaseT hub10BaseT hub

    A B C D E FNIC NIC NIC NIC NIC NIC

    BRIDGE

    HubtoE

    toEG

    NIC

    H

    NIC

    I

    NIC

    J

    NIC

    K

    NIC

    AK = MAC address of NIC

    T MAC addresses are typically 6 bytes long.T 02 60 8c 42 19 7a is an example of a NIC MAC address.

    Standards Organizations and the OSI Model

    IEEE 802.2 LLC

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    Figure 36: IEEE 802.2 LLC

    Important Term

    LLC (logical link control) is the IEEE 802.2 standard on how networks such as Ethernet or

    token ring process information to and from networking protocols.

    LLC is a sublayer of the data link layer and serves as an interface between a variety of

    MAC techniques and the upper-layer protocols. Its functionality is designed to be

    independent of the MAC protocol used.

    The LLC packet is used in IEEE 802.3 CSMA/CD (Carrier Sense Multiple Access/

    Collision Detection), IEEE 802.5 token ring, and ANSI FDDI frames to provide:

    Support to connection-oriented and connectionless services SSAP (source service access point) The address of the entity in the source

    station that originated the communication

    DSAP (destination service access point) The address of the entity in the

    destination station that is to receive the communication

    When LLC is used, it is contained in the first part of the data field of the frame.

    Network protocols

    Logical link control

    Media access control

    Physical

    Interconnecting media

    7

    6

    5

    4

    3

    2

    1

    OSI layers

    UNIX NovellWindows

    NT

    Network protocols

    Logical link control

    Media access control

    Physical

    7

    6

    5

    4

    3

    2

    1

    UNIX NovellWindows

    NT

    Ethernet/token ring/FDDI Ethernet/token ring/FDDI

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    In network layer addressing, the IP (Internet Protocol) address indicates to the routers

    connecting multiple networks which user on which subnet at a specific company the data

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    is intended for.

    For example, in Figure 37, the IP address 172.20.10.17 at the company JBI, Inc. may

    mean the following:

    Figure 38: Network Layer (cont.)

    172 .20 .10 .17

    Up to 254 subnets possible (1254)

    Internet-unique

    (JBI, Inc.)

    z Host address for the subnetz Up to 254 hosts possible (1254)

    Standards Organizations and the OSI Model

    Layer 4 Transport Layer

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    Figure 39: Transport Layer

    The transport layer provides end-to-end integrity between two devices communicating

    through the network.

    The transport layer provides two types of basic services to an upper-layer protocol:

    Connection-oriented services provide feedback about the status data as it

    travels through networks, for example, TCP (Transmission Control Protocol)

    in the TCP/IP stack.

    Connectionless (datagram) service does not provide feedback from the receiver

    about the data, for example, UDP (User Datagram Protocol) in the TCP/IP

    stack.

    The transport layer may support: Data tracking

    Connection flow control

    Sequencing of data

    Error checking

    Application addressing and identification

    In a connection-oriented system, each packet of data is assigned a unique sequence

    number and an associated acknowledgment number to track data as it travels through a

    network. If data is lost or damaged, it is requested to be resent by a device.

    Network

    Acknowledgment

    Acknowledgment

    Data

    Data

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    Connection-Oriented Protocols

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    Figure 40: Connection-Oriented Protocols

    Connection-oriented protocols are designed to provide a high degree of reliability fortraffic as it moves on the network.

    Characteristics of connection-oriented protocols include:

    A connection process (handshake) occurs between two stations before the

    transmission of data. Connections are also referred to as sessions, virtual

    circuits, or logical connections.

    Most connection-oriented protocols require some form of acknowledgmentroutine as data is transmitted. Protocols using acknowledgment routines

    provide a high degree of network reliability.

    Connection-oriented protocols often provide error detection and error recovery

    routines. When data is found to be in error, the sending side is requested to

    retransmit it. Or, if the sending side has not received an acknowledgment, it

    will retransmit the data after a specified period of time.

    When a connection is no longer needed by end users, a defined handshakedrops or takes down the connection.

    TCP is an example of a connection-oriented protocol in the TCP/IP stack.

    Setuprequest

    Setupresponse

    Data

    Connectionclear

    Acknowledgemen

    t

    Clearresponse

    Standards Organizations and the OSI Model

    Connectionless Protocols

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    Figure 41: Connectionless Protocols

    Connectionless protocols do not provide the same high degree of reliability as connection-

    oriented protocols. However, connectionless protocols do offer a significant advantage in

    terms of speed of the transmission.

    Characteristics of connectionless protocols include:

    Connectionless protocols simply send data with a source and destination

    address appended. No setup handshake is done to determine if the destination

    is available.

    Connectionless protocols usually do not support error recovery or

    acknowledgment routines, and would therefore be known as unreliabletransmission services.

    Connectionless protocols are often used because of efficiency and because the

    data does not justify the extra overhead required by connection-oriented

    protocols.

    UDP (User Datagram Protocol) is an example of a connectionless protocol in the TCP/IP

    protocol stack.

    Data

    Data

    Data

    Data

    Standards Organizations and the OSI Model

    Layer 5 Session Layer

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    Figure 42: Session Layer

    Session layer protocols provide the logical connection entities at the application layer.These applications include file transfer protocols and sending e-mail.

    Real-World Application

    Examples of session layer functionality include the establishment, management, and

    termination of connections between applications. If a large graphic needs to be broken up

    in order to send the data out onto the network, the information to put the data back togetheragain would be provided.

    Session layer characteristics include:

    Virtual connection between application entities

    Synchronization of data flow for recovery purposes

    Creation of dialog units and activity units

    Connection parameter negotiation

    Partitioning services into functional groups

    Clientsoftware

    (NOS)

    Serversoftware

    (NOS)

    nServicerequest

    oServiceresponse

    Standards Organizations and the OSI Model

    Layer 6 Presentation Layer

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    Figure 43: Presentation Layer

    The presentation layer specifies how end-user applications should format the data.

    This layer provides for translation between local representations of data and the represen-

    tation of data that will be used for transfer between end-systems. The results of

    encryption, compression, and virtual terminals are examples of this translation service.

    Examples of presentation layer functionality include:

    Encryption and decryption of data

    Compression algorithms

    Character sets, including ASCII and EBCIDIC

    Formatting information

    Network

    Type Options

    ImagesJPEG, PICT,

    GIF

    Video MPEG, MIDI

    DataASCII, EBCIDIC,

    encrypted

    Standards Organizations and the OSI Model

    Layer 7 Application Layer

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    Figure 44: Application Layer

    User application processes require application layer service elements to access thenetworking environment. There are two types of service elements:

    CASEs (common application service elements) Generally are useful to a

    variety of application processes

    SASEs (specific application service elements) Satisfy particular needs of

    application processes

    CASE examples include: Association control that establishes, maintains, and terminates connections

    with a peer application entity

    Commitment, concurrence, and recovery that ensures the integrity of

    distributed transactions

    SASE examples include:

    Figure 45: SASE Examples

    SASE Description Protocol Stack

    FTP File Transfer Protocol TCP/IP

    SNMP Simple Network Management Protocol TCP/IP

    Telnet Virtual terminal protocol TCP/IP

    SMTP Simple Mail Transfer Protocol TCP/IP

    PC Applications

    Database

    Word processing

    Spreadsheets

    Networking Applications

    File transfer

    E-mail