Chapter One An Introduction to Networking. Networks and Standalone Computers Network Group of computers and other devices connected by some type of transmission

Chapter OneChapter OneAn IntroductionAn Introduction

to Networkingto Networking

Networks and Standalone Networks and Standalone ComputersComputers

NetworkNetwork Group of computers and other devices Group of computers and other devices

connected by some type of transmission mediaconnected by some type of transmission media Networks enable users to share devices and Networks enable users to share devices and

data, collectively called a network’s data, collectively called a network’s resourcesresources

Standalone computerStandalone computer Uses programs and data only from its local Uses programs and data only from its local

disks and is not connected to a networkdisks and is not connected to a network

Standalone ComputersStandalone Computers

Method of sharing data by copying it to a disk Method of sharing data by copying it to a disk and carrying the disk from computer to computerand carrying the disk from computer to computer

Figure 1-1: Data sharing before the advent of networks

Network

NetworkNetwork

A A NetworkNetwork is an Any-to-Any is an Any-to-Any Communication SystemCommunication System Can connect any Can connect any stationstation to any other to any other

Advantages of a Network in an Office SettingAdvantages of a Network in an Office Setting

Recourse Sharing- All office members can share computer files - Laser printers can be shared-Software applications are more easily shared and upgraded

Electronic mail can be implemented Office computers can be backed up over the network Working groups can share information within the each group Saving money :- In a distributed network computers have a

better price/performance ratio as compared to large ones.E.g. Mainframes are 10 times faster than personal computers, but they cost 1000 times more.

Basic Components of NetworkBasic Components of Network

Workstations

Network Operating System

Cabling

Basic Network ComponentsBasic Network ComponentsBasic Network ComponentsBasic Network Components

Workstation Workstation

Workstation

Workstation

File Server with NTServer Operating System

Cabling

Networking BasicsNetworking Basics

WorkstationWorkstation Computer that typically runs a desktop operating Computer that typically runs a desktop operating

system and connects to a networksystem and connects to a network

Client/server architectureClient/server architecture Networking model in which clients use central Networking model in which clients use central

server to share applications, devices, and dataserver to share applications, devices, and data

Network operating systemNetwork operating system Special software designed to manage data and Special software designed to manage data and

other resources on a server for a number of clientsother resources on a server for a number of clients

Terminal-Host SystemsTerminal-Host Systems(Mainframe Architecture)(Mainframe Architecture)

Central Central host computerhost computer does all the processing does all the processing TerminalTerminal is dumb--only a remote screen and is dumb--only a remote screen and

keyboardkeyboard Host are mainframesHost are mainframes

Terminals Host

Distributed NetworksDistributed Networks((Client/Server Architecture)Client/Server Architecture)

The Most Common Platform in OrganizationsThe Most Common Platform in Organizations Based on Client/Server ArchitectureBased on Client/Server Architecture Allows PCs to share resourcesAllows PCs to share resources

Network

ClientPC

ClientPC

PC E-mail Server

PC File Server

Client / ServerClient / Server

Networked ComputersNetworked Computers

ClientClient User (PC, Workstation, Laptop) Requires User (PC, Workstation, Laptop) Requires

Data, Application, Communications It Does Data, Application, Communications It Does Not HaveNot Have

ServerServer Component (Computer) Having Desired Data, Component (Computer) Having Desired Data,

Application, CommunicationsApplication, Communications

Client/Server ProcessingClient/Server Processing

Cooperation Through Message ExchangeCooperation Through Message Exchange

Client program sends Client program sends Request messageRequest message, such as , such as a database retrieval requesta database retrieval request

Server program sends a Server program sends a Response messageResponse message to to deliver the requested information or an deliver the requested information or an explanation for failureexplanation for failure

Client Machine Server

Client ProgramServer

Program

Request

Response

PC Network ComponentsPC Network Components

File ServersFile Servers Store files (data files and programs)Store files (data files and programs) The most common type of server in PC The most common type of server in PC

networksnetworks Almost all file servers are themselves PCsAlmost all file servers are themselves PCs

File Server

File Server Program AccessFile Server Program Access

File Server Program AccessFile Server Program Access is the Most Common Way is the Most Common Way to Execute Programs in PC Networksto Execute Programs in PC Networks Program files are Program files are storedstored on the file server on the file server But downloaded (copied) to client PC for executionBut downloaded (copied) to client PC for execution Executed on client PC, not on file serverExecuted on client PC, not on file server

File ServerClient PC

Storedon the

FileServer

Download

Executedon

Client PC

LANs – WANs - MANsLANs – WANs - MANs

Networks Have Different Geographical ScopesNetworks Have Different Geographical ScopesLocal Area Networks (LANs)Local Area Networks (LANs) Small OfficeSmall Office Office BuildingOffice Building University CampusUniversity Campus

Wide Area Networks (WANs)Wide Area Networks (WANs) Connect Customer and Supplier across various Connect Customer and Supplier across various

building within a city.building within a city.

Metropolitan Area Network (MAN)Metropolitan Area Network (MAN) Connect corporate sites across citiesConnect corporate sites across cities

Local Area Network (LAN)Local Area Network (LAN)

Network of computers and other devices Network of computers and other devices confined to relatively small spaceconfined to relatively small space

LANs involving many computers are LANs involving many computers are usually server-basedusually server-based On a On a server-based networkserver-based network, special , special

computers (known as computers (known as serversservers) process data ) process data for and facilitate communication between for and facilitate communication between other computers on the network (known as other computers on the network (known as clientsclients))

Figure 1-3: LAN with a file

server

Small Peer-Peer PC NetworkSmall Peer-Peer PC Network

No dedicated (full-No dedicated (full-time) servertime) server

User PCs supply User PCs supply services to each services to each otherother

So user PCs act So user PCs act both as clients and both as clients and as serversas servers


File SharingFile Sharing

Each PC can make Each PC can make certain disk drives or certain disk drives or directories available directories available to to other user PCsto to other user PCs

Can allow others Can allow others read-only or full read-only or full access to files thereaccess to files there

Can require Can require password for accesspassword for access


Printer SharingPrinter Sharing

Each PC can make one Each PC can make one or more printers or more printers attached to it available to attached to it available to othersothers

Windows 95 can be Windows 95 can be used as for Peer – to – used as for Peer – to – peer network.peer network.

Windows NT can also be Windows NT can also be used but it is designed to used but it is designed to work in a centralized work in a centralized networking modelnetworking model


AdvantageAdvantage

No dedicated No dedicated server to server to purchase and purchase and maintainmaintain


DisadvantagesDisadvantages

If someone turns If someone turns off their PC or off their PC or crashes it, people crashes it, people using its files or using its files or printer are cut outprinter are cut out


Disadvantages (Cont.)Disadvantages (Cont.)

Users often set up Users often set up security poorly giving security poorly giving access to unauthorized access to unauthorized peoplepeople

Special problem if home Special problem if home network is connected to network is connected to the Internetthe Internet

Experience slow Experience slow response if heavily response if heavily loaded.loaded.


OverallOverall

Beyond about 5 Beyond about 5 users, problems users, problems become become pronouncedpronounced

Beyond about 10 Beyond about 10 users, very bad users, very bad ideaidea

MANs and WANsMANs and WANs

Metropolitan area network (MAN)Metropolitan area network (MAN) Network connecting clients and servers in Network connecting clients and servers in

multiple buildings within limited geographic multiple buildings within limited geographic areaarea

Wide area network (WAN)Wide area network (WAN) Network that spans large distance and Network that spans large distance and

connects two or more LANsconnects two or more LANs The The InternetInternet is an example of a very intricate is an example of a very intricate

and extensive WAN that spans the globeand extensive WAN that spans the globe

WANWAN

Figure 1-5: A simple

WAN

Elements Common to AllElements Common to AllServer-Based NetworksServer-Based Networks

ClientClient In addition to referring to a computer on the network, In addition to referring to a computer on the network,

may also refers to human may also refers to human useruser of client workstation of client workstation

Server – It runs the NOS ( Eg. UNIX, NT4.0)Server – It runs the NOS ( Eg. UNIX, NT4.0)

Cabling Cabling

Network interface card (NIC)Network interface card (NIC) Enables workstation to connect to the network and Enables workstation to connect to the network and

communicate with other computerscommunicate with other computers


Figure 1-6: A network interface

card (NIC)

ServersServers Provide services to client PCsProvide services to client PCs

Usually PCs themselvesUsually PCs themselves

Most PC nets have multiple serversMost PC nets have multiple servers

Require a NICRequire a NIC

Require a server operating Require a server operating system (SOS)system (SOS)

Require application softwareRequire application software

Server Operating System (SOS)Server Operating System (SOS) Servers need operating systems more reliable Servers need operating systems more reliable

than client PC operating systemsthan client PC operating systems

Windows NT/2000 Server, Novell NetWare, UNIX, Windows NT/2000 Server, Novell NetWare, UNIX, LINUXLINUX

Application SoftwareApplication Software Provides the services offered by the serversProvides the services offered by the servers

E-mail, word processing, file sharing, etc.E-mail, word processing, file sharing, etc.

More expensive than the SOSMore expensive than the SOS

Novell NetWareNovell NetWare SOS SOS Once dominant, but market share has Once dominant, but market share has

shrunkshrunk

Excellent file and print serviceExcellent file and print service

Excellent directory service (later)Excellent directory service (later)

Until recently, was not sufficiently robust Until recently, was not sufficiently robust and scalable for servers other than file and scalable for servers other than file serversservers

Microsoft Windows ServerMicrosoft Windows Server Operating System Operating System More robust than desktop Windows (Win 95, Win More robust than desktop Windows (Win 95, Win

98, Win 2000 Professional, etc.)98, Win 2000 Professional, etc.)

All 32-bit codeAll 32-bit code

Microsoft Windows NT Server before 2000Microsoft Windows NT Server before 2000

Newer Microsoft Windows 2000 ServerNewer Microsoft Windows 2000 Server

Versions in order of increasing functionality: Windows Versions in order of increasing functionality: Windows 2000 Server, Advanced Server, DataCenter Server2000 Server, Advanced Server, DataCenter Server

New

Microsoft Windows Server Operating Microsoft Windows Server Operating SystemSystem Easy to install, learn, and use because Easy to install, learn, and use because

resembles desktop Windowsresembles desktop Windows

Becoming dominant for small business and Becoming dominant for small business and small department serverssmall department servers

UNIXUNIX Powerful workstation servers run UNIXPowerful workstation servers run UNIX

Extremely reliableExtremely reliable

Workstation servers running UNIX Workstation servers running UNIX dominate the enterprise server marketdominate the enterprise server market

UNIXUNIX Expensive to buyExpensive to buy

Must retrain staff or hire UNIX staffMust retrain staff or hire UNIX staff

Many versions of UNIX existMany versions of UNIX existMost run the same application softwareMost run the same application software

However, have different management utilities, However, have different management utilities, etc., requiring training for each version usedetc., requiring training for each version used

Not for Small PC NetworksNot for Small PC Networks

Server Application SoftwareServer Application Software

File Service Allows File SharingFile Service Allows File Sharing File server stores program and data filesFile server stores program and data files Shared file be accessed by any user with Shared file be accessed by any user with

access rightsaccess rights Built into most SOSsBuilt into most SOSs

FileServer

Access Rights

No Access Rights


File ServiceFile Service For sharing application program files alsoFor sharing application program files also No need to install applications on each PCNo need to install applications on each PC

Greatly reduces installation laborGreatly reduces installation labor

FileServer


File Server Program AccessFile Server Program Access Program is STORED on the file serverProgram is STORED on the file server

FileServer


File Server Program AccessFile Server Program Access But program is EXECUTED on the client PCBut program is EXECUTED on the client PC Limited by power of client PCs, which do not Limited by power of client PCs, which do not

get very largeget very large

FileServer


Print ServicePrint Service Also built into SOSsAlso built into SOSs Print jobs go to shared printersPrint jobs go to shared printers But they But they firstfirst go to the file server go to the file server Not directly to the print server!Not directly to the print server!

File Server

Print Server

SharedPrinterClient PC


Print ServicePrint Service File server stores print job in a print queue until print File server stores print job in a print queue until print

server is ready to print itserver is ready to print it File server sends the print job to the print serverFile server sends the print job to the print server

File Server

Print Server

SharedPrinter


Print ServerPrint Server Print server feeds the print job to the printerPrint server feeds the print job to the printer Print servers are simple and inexpensive because the Print servers are simple and inexpensive because the

file server does most of the workfile server does most of the work Low print server cost allows shared printers can be Low print server cost allows shared printers can be

scattered throughout the officescattered throughout the office

File Server

Print Server


Typical Application SoftwareTypical Application Software

Word processing, e-mail, etc.Word processing, e-mail, etc.

Must buy multiuser versions, not just a single Must buy multiuser versions, not just a single copy from a retail storecopy from a retail store

License will limit the number of usersLicense will limit the number of users

Will cost more than the SOSWill cost more than the SOS


Remote Access Service (RAS)Remote Access Service (RAS) User dials into a remote access serverUser dials into a remote access server Server authenticates the user (user must prove Server authenticates the user (user must prove

identity)identity) If authenticated, user may use internal serversIf authenticated, user may use internal servers Client PC needs RAS softwareClient PC needs RAS software

LAN

InternalServer

RAS

Dial-InClient

Dial-UpTelephone

Line

RASClient

Software


Directory ServersDirectory Servers Problem: Most networks have many Problem: Most networks have many

serversservers To use a resource, must know the serverTo use a resource, must know the server

To send e-mail, address is user@serverTo send e-mail, address is user@server

Files must be accessed on particular serversFiles must be accessed on particular servers


Directory ServersDirectory Servers Directory server knows all resources on all Directory server knows all resources on all

serversservers Can send mail to user (without @server)Can send mail to user (without @server) Can search for a specific file across Can search for a specific file across

serversserversDirectory

Server


Directory ServersDirectory Servers Know user access rights on all serversKnow user access rights on all servers Single login to directory serverSingle login to directory server After that, get access to all other servers After that, get access to all other servers

where user has access rightswhere user has access rights

DirectoryServer

SingleLogin


TopologyTopology Physical Physical

layout of layout of computer computer networknetwork

Figure 1-7: Commonly used network topologies

An Ethernet Bus NetworkAn Ethernet Bus Network

Pencomputer

Terminator

File Sever

File Sever

DesktopComputer

DesktopComputer

LaptopComputer

LaserPrinter

The Ring TopologyThe Ring Topology

Ring

Workstation

Workstation

Workstation

File Server

Ethernet Star Topology with a ConcentratorEthernet Star Topology with a Concentrator

Concentrator

UTPCabling

Workstation Workstation

File Server


ProtocolProtocol Rules network uses to transfer dataRules network uses to transfer data

NetBEUI (native to NT Server)

TCP/IP (important for networks with UNIX, Internet

communications)

IPX/SPX (for communications on networks with Novell Netware)

Data PacketsData Packets The distinct units of data transmitted from one The distinct units of data transmitted from one

computer to another on a networkcomputer to another on a network


AddressingAddressing Scheme for assigning unique identifying Scheme for assigning unique identifying

number to every workstation on networknumber to every workstation on network The number that uniquely identifies each The number that uniquely identifies each

workstation and device on a network is its workstation and device on a network is its addressaddress


Transmission Transmission mediamedia Means Means

through through which data which data are are transmitted transmitted and receivedand received

Figure 1-8: Examples of network transmission media

How Networks Are UsedHow Networks Are Used

ServicesServices Features provided by a networkFeatures provided by a network

File and print servicesFile and print services

Communications servicesCommunications services

Mail servicesMail services

Internet servicesInternet services

Management servicesManagement services

Network ServicesNetwork Services

File servicesFile services Refers to capability of a server to share data Refers to capability of a server to share data

files, applications, and disk storage spacefiles, applications, and disk storage space Server that provides file services is called a Server that provides file services is called a

file serverfile server

Print servicesPrint services Allows printers to be shared by several users Allows printers to be shared by several users

on a networkon a network


Communications servicesCommunications services Allow remote users to connect to a networkAllow remote users to connect to a network

Remote userRemote user Person working on a computer in a different Person working on a computer in a different

geographical location from the LAN’s servergeographical location from the LAN’s server

Communications serverCommunications serverServer that runs communications servicesServer that runs communications services

Also referred to as Also referred to as access serversaccess servers and and remote remote access serversaccess servers


Mail servicesMail services Coordinate storage and transfer of e-mail Coordinate storage and transfer of e-mail

between users on a networkbetween users on a networkGatewayGateway

Combination of software and hardware enabling two Combination of software and hardware enabling two different kinds of networks to exchange datadifferent kinds of networks to exchange data

Internet servicesInternet services Enable networks to communicate with the Enable networks to communicate with the

InternetInternet


Management servicesManagement services Centrally administer and simplify complicated Centrally administer and simplify complicated

management tasks on the networkmanagement tasks on the network Numerous services fall under category of Numerous services fall under category of

network managementnetwork management

Documents

Chapter One An Introduction to Networking. Networks and Standalone Computers Network Group of computers and other devices connected by some type of transmission