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CSCI-235CSCI-235Micro-Computer ApplicationsMicro-Computer Applications
The NetworkThe Network
© Prentice-Hall, Inc
Network FundamentalsNetwork Fundamentals A computer A computer networknetwork consists of consists of
two or more computers linked two or more computers linked together to exchange data and together to exchange data and share resourcesshare resources
CommunicationCommunication is the process is the process of sending and receiving of sending and receiving messagesmessages
Communication channelsCommunication channels are are the paths through which the paths through which messages are passedmessages are passed
Communication devicesCommunication devices transform electronic signals transform electronic signals
© Prentice-Hall, Inc
Putting Together a NetworkPutting Together a Network
Basic ComponentsBasic Components Sending deviceSending device Communications linkCommunications link Receiving deviceReceiving device
A Communications ModelA Communications 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
Simplified Communications Simplified Communications Model - DiagramModel - Diagram
Simplified Data Simplified Data Communications ModelCommunications Model
Continuous & Discrete SignalsContinuous & Discrete Signals
Frequency Domain ConceptsFrequency Domain Concepts
Signal usually made up of many Signal usually made up of many frequenciesfrequencies
Components are sine wavesComponents are sine waves Can be shown (Can be shown (Fourier analysisFourier analysis) that any ) that any
signal is made up of component sine signal is made up of component sine waveswaves
Can plot frequency domain functionsCan plot frequency domain functions
Addition of Frequency Addition of Frequency ComponentsComponents
© Prentice-Hall, Inc
Data Rate and BandwidthData Rate and Bandwidth
Any transmission system has a limited Any transmission system has a limited band of frequenciesband of frequencies
This limits the This limits the data ratedata rate that can be carried that can be carried
BandwidthBandwidth BandwidthBandwidth is usually used to refer to the data is usually used to refer to the data
rate (i.e., the amount of data that can be rate (i.e., the amount of data that can be transmitted through a communications transmitted through a communications channel)channel)
Digital bandwidth is measured in bits per Digital bandwidth is measured in bits per second (bps), kilobits per second (Kbps), second (bps), kilobits per second (Kbps), megabits per second (Mbps), or gigabits per megabits per second (Mbps), or gigabits per second (Gbps)second (Gbps)
Low bandwidth is 56 Kbps and high bandwidth Low bandwidth is 56 Kbps and high bandwidth is 622 Mbpsis 622 Mbps
© Prentice-Hall, Inc
Modulation
DigitalAnalog
Analog Digital
Demodulation
Modems: From Digital to Analog Modems: From Digital to Analog and Backand Back
ModemsModems are devices that transform signals when are devices that transform signals when sending and receiving transmissionssending and receiving transmissions ModulationModulation – Transforming digital signals to analog – Transforming digital signals to analog DemodulationDemodulation – Transforming analog signals to digital – Transforming analog signals to digital
NetworkingNetworking
Point to point communication not usually Point to point communication not usually practicalpractical Devices are too far apartDevices are too far apart Large set of devices would need impractical Large set of devices would need impractical
number of connectionsnumber of connections Solution is a communications networkSolution is a communications network
© Prentice-Hall, Inc
Circuit switchingCircuit switching Networks create an end-Networks create an end-
to-end circuit between the to-end circuit between the sending and receiving sending and receiving computerscomputers
Electronic switches Electronic switches establish and maintain establish and maintain the connectionthe connection
Switching and Routing TechniquesSwitching and Routing TechniquesPacket switchingPacket switching
Outgoing messages are Outgoing messages are divided into fixed-size divided into fixed-size data units called data units called packetspackets
Packets are numbered Packets are numbered and addressed to the and addressed to the receiving computerreceiving computer
Routers examine the Routers examine the packets and send them to packets and send them to
their destinationtheir destination
© Prentice-Hall, Inc
AdvantagesAdvantages DisadvantagesDisadvantages
CircuitCircuit switchingswitchingVoice and real-time Voice and real-time transmissiontransmission
No delivery delaysNo delivery delays
CostlyCostly
A direct electrical A direct electrical connection between connection between the computers is the computers is requiredrequired
Packet switchingPacket switching
Efficient, less Efficient, less expensive, and expensive, and reliablereliable
Will function if part Will function if part of the network is of the network is downdown
Delays in receiving Delays in receiving packetspackets
Not ideal for real-Not ideal for real-time voice time voice communicationcommunication
Advantages and Disadvantages Advantages and Disadvantages of Circuit and Packet Switchingof Circuit and Packet Switching
© Prentice-Hall, Inc
ProtocolsProtocolsProtocolsProtocols are fixed, formalized standards are fixed, formalized standards
that specify how computers can that specify how computers can communicate over a networkcommunicate over a network
© Prentice-Hall, Inc
Network LayersNetwork Layers
Network architecture is the overall design of a networkNetwork architecture is the overall design of a network The network design is divided into layers, each of which The network design is divided into layers, each of which
has a function separate from that of the other layershas a function separate from that of the other layers Protocol stackProtocol stack – The vertical (top to bottom) arrangement – The vertical (top to bottom) arrangement
of the layers; each layer is governed by its own set of of the layers; each layer is governed by its own set of protocolsprotocols
user
physical media
user
physical media
receiving
sending
protocol
layerstack
© Prentice-Hall, Inc
Reduced hardware costsReduced hardware costs
Users share equipmentUsers share equipment
Connected peopleConnected people People can work People can work
together without being together without being at the same locationat the same location
Groupware enables Groupware enables sharing of schedules sharing of schedules and communicationsand communications
Advantages of NetworkingAdvantages of Networking
Shared applicationsShared applications Users share softwareUsers share software File server enables all File server enables all
users to work with the users to work with the same application program same application program
Building information Building information resourcesresources
Users create common Users create common pools of data that can be pools of data that can be accessed by employeesaccessed by employees
© Prentice-Hall, Inc
Local Area Network Local Area Network (LAN)(LAN)
Links computers within a Links computers within a building or group of building or group of buildingsbuildings
Uses direct cables, radio, Uses direct cables, radio, or infrared signalsor infrared signals
Types of Computer NetworksTypes of Computer Networks
Wide Area Network Wide Area Network (WAN)(WAN)
Links computers separated Links computers separated by a few miles or by a few miles or thousands of milesthousands of miles
Uses long-distance Uses long-distance transmission mediatransmission media
© Prentice-Hall, Inc
Local Area Networks (LANs)Local Area Networks (LANs) Network access is controlled by a network Network access is controlled by a network
administratoradministrator
Users can access software, data, and Users can access software, data, and peripheralsperipherals
LANs require special hardware and softwareLANs require special hardware and software
Computers connected to a LAN are called Computers connected to a LAN are called workstations workstations or or nodesnodes
© Prentice-Hall, Inc
LAN Hardware and SoftwareLAN Hardware and Software
Networking HardwareNetworking HardwareNetwork interface card Network interface card
(NIC)(NIC) – Provides the – Provides the connection between the connection between the computer and the networkcomputer and the network
Inserted into a computer’s Inserted into a computer’s expansion slotexpansion slot
Networking SoftwareNetworking SoftwareOperating system that Operating system that
supports networking supports networking (Unix, Linux, Windows, (Unix, Linux, Windows, Mac OS)Mac OS)
Additional system Additional system softwaresoftware
NIC
© Prentice-Hall, Inc
Peer-to-Peer NetworksPeer-to-Peer Networks
All computers on the network are treated as equalAll computers on the network are treated as equalUsers decide which files and peripherals to shareUsers decide which files and peripherals to sharePeer-to peer is not suited for networks with many Peer-to peer is not suited for networks with many
computerscomputersPeer-to-peer is easy to set up. Example: home networksPeer-to-peer is easy to set up. Example: home networks
© Prentice-Hall, Inc
Client-Server NetworksClient-Server Networks
Typical corporate networks are Typical corporate networks are client-serverclient-server
Clients send requests to servers for programs Clients send requests to servers for programs and data, and to access peripheralsand data, and to access peripherals
© Prentice-Hall, Inc
Wide Area Networks (WANs)Wide Area Networks (WANs)
WANsWANs are similar to long-distance are similar to long-distance telephone systemstelephone systems
© Prentice-Hall, Inc
WAN ApplicationsWAN Applications
LAN-to-LANLAN-to-LAN WANs are used to connect LANs at two or WANs are used to connect LANs at two or
more geographic locationsmore geographic locations
Companies use WANs to connect their Companies use WANs to connect their branches to one network systembranches to one network system
© Prentice-Hall, Inc
BackbonesBackbones
BackbonesBackbones, high-capacity transmission lines, , high-capacity transmission lines, are regional, continental, or transcontinentalare regional, continental, or transcontinental
Internet backbones can carry 2.5 gigabits of Internet backbones can carry 2.5 gigabits of data per seconddata per second