Chapter One An Introduction to Networking. Networks and Standalone Computers Network Group of...
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Transcript of Chapter One An Introduction to Networking. Networks and Standalone Computers Network Group of...
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
Small Peer-Peer PC NetworkSmall Peer-Peer PC Network
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
Small Peer-Peer PC NetworkSmall Peer-Peer PC Network
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
Small Peer-Peer PC NetworkSmall Peer-Peer PC Network
AdvantageAdvantage
No dedicated No dedicated server to server to purchase and purchase and maintainmaintain
Small Peer-Peer PC NetworkSmall Peer-Peer PC Network
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
Small Peer-Peer PC NetworkSmall Peer-Peer PC Network
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.
Small Peer-Peer PC NetworkSmall Peer-Peer PC Network
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
Elements Common to AllElements Common to AllServer-Based NetworksServer-Based Networks
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
Server Application SoftwareServer Application Software
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
Server Application SoftwareServer Application Software
File Server Program AccessFile Server Program Access Program is STORED on the file serverProgram is STORED on the file server
FileServer
Server Application SoftwareServer Application Software
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
Server Application SoftwareServer Application Software
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
Server Application SoftwareServer Application Software
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
Server Application SoftwareServer Application Software
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
Server Application SoftwareServer Application Software
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
Server Application SoftwareServer Application Software
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
Server Application SoftwareServer Application 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
Server Application SoftwareServer Application Software
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
Server Application SoftwareServer Application Software
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
Elements Common to AllElements Common to AllServer-Based NetworksServer-Based Networks
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
Elements Common to AllElements Common to AllServer-Based NetworksServer-Based Networks
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
Elements Common to AllElements Common to AllServer-Based NetworksServer-Based Networks
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
Elements Common to AllElements Common to AllServer-Based NetworksServer-Based Networks
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
Network ServicesNetwork Services
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
Network ServicesNetwork Services
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
Network ServicesNetwork Services
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