computer network - basic concepts

IntroductionIntroduction
toto
Computer AdministrationComputer Administration

Computer Network -Computer Network -
Basic ConceptsBasic Concepts
 Computer NetworksComputer Networks
 Communication ModelCommunication Model
 Transmission ModesTransmission Modes
 Communication TypesCommunication Types
 Classification Of Computer NetworksClassification Of Computer Networks
 By ScaleBy Scale
 By StructureBy Structure
 By TopologyBy Topology
 Network MediaNetwork Media
 InternetworkingInternetworking

Computer NetworkComputer Network
 A computer network is a group of interconnectedA computer network is a group of interconnected
computers.computers.
 It allows computers to communicate with each other andIt allows computers to communicate with each other and
to share resources and information.to share resources and information.
 First Network : The Advanced Research Projects AgencyFirst Network : The Advanced Research Projects Agency
(ARPA) funded the design of the "Advanced Research(ARPA) funded the design of the "Advanced Research
Projects Agency Network" (ARPANET) for the UnitedProjects Agency Network" (ARPANET) for the United
States Department of DefenseStates Department of Defense

Communication ModelCommunication Model

Communication ModelCommunication Model
 SourceSource
 generates data to be transmittedgenerates data to be transmitted
 TransmitterTransmitter
 Converts data into transmittable signalsConverts data into transmittable signals
 Transmission SystemTransmission System
 Carries dataCarries data
 ReceiverReceiver
 Converts received signal into dataConverts received signal into data
 DestinationDestination
 Takes incoming dataTakes incoming data

Transmission ModesTransmission Modes
 SimplexSimplex
 One directionOne direction
 e.g. Televisione.g. Television
 Half duplexHalf duplex
 Either direction, butEither direction, but
only one way at a timeonly one way at a time
 e.g. police radioe.g. police radio
 Full duplexFull duplex
 Both directions at theBoth directions at the
same timesame time
 e.g. telephonee.g. telephone

Communication TypesCommunication Types
 Unicasting (one-to-one)Unicasting (one-to-one)
 Multicasting (one-to-many)Multicasting (one-to-many)
 Broadcasting (one-to-all)Broadcasting (one-to-all)

Network ClassificationNetwork Classification
 By Size or ScaleBy Size or Scale
 LANLAN
 WANWAN
 MANMAN
 CANCAN
 PANPAN

Local Area Network (LAN)Local Area Network (LAN)
 Contains printers, servers and computersContains printers, servers and computers
 Systems are close to each otherSystems are close to each other
 Contained in one office or buildingContained in one office or building
 Organizations often have several LANSOrganizations often have several LANS

Wide Area Networks (WAN)Wide Area Networks (WAN)
 Two or more LANs connectedTwo or more LANs connected
 Over a large geographic areaOver a large geographic area
 Typically use public or leased linesTypically use public or leased lines
 Phone linesPhone lines
 SatelliteSatellite
 The Internet is a WANThe Internet is a WAN

Metropolitan Area Network (MAN)Metropolitan Area Network (MAN)
 Large network that connects differentLarge network that connects different
organizationsorganizations
 Shares regional resourcesShares regional resources
 A network provider sells timeA network provider sells time

Campus Area Networks (CAN)Campus Area Networks (CAN)
 A LAN in one large geographic areaA LAN in one large geographic area
 Resources related to the sameResources related to the same
organizationorganization
 Each department shares the LANEach department shares the LAN

Personal Area Network (PAN)Personal Area Network (PAN)
 Very small scale networkVery small scale network
 Range is less than 2 metersRange is less than 2 meters
 Cell phones, PDAs, MP3 playersCell phones, PDAs, MP3 players

 By Structure / Functional RelationshipBy Structure / Functional Relationship
 Client / ServerClient / Server
 Peer to Peer (P2PN)Peer to Peer (P2PN)

Client/Server networkClient/Server network
 Nodes and servers share data rolesNodes and servers share data roles
 Nodes are called clientsNodes are called clients
 Servers are used to control accessServers are used to control access
 Database softwareDatabase software
 Access to data controlled by serverAccess to data controlled by server
 Server is the most important computerServer is the most important computer

Peer to peer networks (P2PN)Peer to peer networks (P2PN)
 All nodes are equalAll nodes are equal
 Nodes access resources on other nodesNodes access resources on other nodes
 Each node controls its own resourcesEach node controls its own resources
 Most modern OS allow P2PNMost modern OS allow P2PN
 Distributed computing is a formDistributed computing is a form
 KazaaKazaa

 By Topology / Physical ConnectivityBy Topology / Physical Connectivity
 BUSBUS
 STARSTAR
 RINGRING
 MESHMESH
 TREETREE

Network TopologyNetwork Topology
 Logical layout of wires and equipmentLogical layout of wires and equipment
 Choice affectsChoice affects
 Network performanceNetwork performance
 Network sizeNetwork size
 Network collision detectionNetwork collision detection

BUSBUS
 Also called linear busAlso called linear bus
 One wire connects all nodesOne wire connects all nodes
 Terminator ends the wiresTerminator ends the wires
 AdvantagesAdvantages
 Easy to setupEasy to setup
 Small amount of wireSmall amount of wire
 DisadvantagesDisadvantages
 SlowSlow
 Easy to crashEasy to crash

STARSTAR
 All nodes connect to a hubAll nodes connect to a hub
 Packets sent to hubPackets sent to hub
 Hub sends packet to destinationHub sends packet to destination
 One cable can not crash networkOne cable can not crash network
 One hub crashing downs entire networkOne hub crashing downs entire network
 Uses lots of cableUses lots of cable
 Most common topologyMost common topology

RINGRING
 Nodes connected in a circleNodes connected in a circle
 Tokens used to transmit dataTokens used to transmit data
 Nodes must wait for token to sendNodes must wait for token to send
 Time to send data is knownTime to send data is known
 No data collisionsNo data collisions
 SlowSlow
 Lots of cableLots of cable

MESHMESH
 All computers connected togetherAll computers connected together
 Internet is a mesh networkInternet is a mesh network
 AdvantageAdvantage
 Data will always be deliveredData will always be delivered
 Lots of cableLots of cable
 Hard to setupHard to setup

TREETREE
 Hierarchal ModelHierarchal Model
 ScaleableScaleable
 Easy ImplementationEasy Implementation
 Easy TroubleshootingEasy Troubleshooting

Network MediaNetwork Media
 Links that connect nodesLinks that connect nodes
 Choice impactsChoice impacts
 SpeedSpeed
 SecuritySecurity
 SizeSize

Twisted-pair cablingTwisted-pair cabling
 Most common LAN cableMost common LAN cable
 Called Cat5 or 100BaseTCalled Cat5 or 100BaseT
 Four pairs of copper cable twistedFour pairs of copper cable twisted
 May be shielded from interferenceMay be shielded from interference
 Speeds range fromSpeeds range from
1 Mbps to 1,000 Mbps1 Mbps to 1,000 Mbps

Coaxial cableCoaxial cable
 Similar to cable TV wireSimilar to cable TV wire
 One wire runs through cableOne wire runs through cable
 Shielded from interferenceShielded from interference
 Speeds up to 10 MbpsSpeeds up to 10 Mbps
 Nearly obsoleteNearly obsolete

Fiber-optic cableFiber-optic cable
 Data is transmitted with light pulsesData is transmitted with light pulses
 Glass strand instead of cableGlass strand instead of cable
 Immune to interferenceImmune to interference
 Very secureVery secure
 Hard to work withHard to work with
 Speeds up toSpeeds up to
100 Gbps100 Gbps

Wireless MediaWireless Media
 Data transmitted through the airData transmitted through the air
 LANs use radio wavesLANs use radio waves
 WANs use microwave signalsWANs use microwave signals
 Difficult to secureDifficult to secure

Internetwork
 An Internetwork is the connection of two or more
distinct computer networks or network segments
via a common routing technology.
 Any interconnection among or between public,
private, commercial, industrial, or governmental
networks may also be defined as an
internetwork.

InternetworkInternetwork
 Intranet
 An intranet is a set of networks, using the Internet Protocol and IP-based tools
such as web browsers and file transfer applications, that is under the control of a
single administrative entity.
 Most commonly, an intranet is the internal network of an organization
 Extranet
 An extranet is a network or internetwork that is limited in scope to a single
organization or entity but which also has limited connections to the networks of
one or more other usually, but not necessarily, trusted organizations or entities
 by definition, an extranet cannot consist of a single LAN; it must have at least
one connection with an external network.
 Internet
 The Internet consists of a worldwide interconnection of governmental, academic,
public, and private networks based upon the networking technologies of the
Internet Protocol Suite.
 It is the successor of the Advanced Research Projects Agency Network
(ARPANET) developed by DARPA of the U.S. Department of Defense.
 The Internet is also the communications backbone underlying the World Wide
Web (WWW).

computer network - basic concepts

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