computer communication and...
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Computer Communication and Networks
Dr. Atiq Ahmed
Department of Computer Science & Information TechnologyUniversity of Balochistan
Lecture 02
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Outline
1 IntroductionTopologiesNetwork TechnologiesProtocolNetwork Functions
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Network Topologies
Map of a network
Defines how the nodes of a network are connected
Three basic categories
Physical topology
Signal topology
Logical topology
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Physical Topologies
Describe the layout of the cables and workstations and thelocation of all network components
Figure: Physical Topology Types
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Signal Topologies
Describes the mapping of the actual connections betweenthe nodes of a network
Point-to-point (PTP) topology
Figure: Point-to-Point Topology Types
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Logical Topologies
Describe the mapping of the apparent connections betweenthe nodes of a network
Are bound to network protocols and describe how data ismoved across the network
Are often closely associated with media access control(MAC) methods
Are able to be dynamically reconfigured by special types ofequipment such as routers and switches
NoteA network can have one type of ’physical topology and acompletely different logical topology
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Network Technologies
No generally accepted taxonomy into which all computernetworks fit
Two dimensions stand out as important
Transmission TechnologyScale
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Generalized Classification of Networks
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Classification Based on TransmissionTechnology
Broadly categorized into two types
Broadcast networksHave a single communication channel that is shared by all themachines on the network
Machines on the network receive short messages, calledpackets
Address field within the packet specifies the intended recipient
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Class. Based on Transmission TechnologyBroadcast networks
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Class. Based on Transmission TechnologyPoint-to-Point Networks
Point-to-Point Networks
End devices that wish tocommunicate are calledstations
Switching devices are callednodes
There may exist multiplepaths between asource-destination pair forbetter network reliability
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Classification based on Scale
Personal Area Network (PAN)
Local Area Network (LAN)
Campus Area Network (CAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
Global Area Network (GAN)
InternetworkIntranetExtranetInternet
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Classification based on ScaleLocal Area Network (LAN)
Usually privately owned
Links the devices in a single office, building or campus of upto few kilometers in size
Used to share resources (hardware or software) and toexchange information
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Classification based on ScaleLocal Area Network (LAN)
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Classification based on ScaleMetropolitan Area Networks (MAN)
Designed to extend over the entire city
May be a single network as a cable TV network or it may beconnecting a number of LANs into a larger network
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Classification based on ScaleMetropolitan Area Networks (MAN)
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Classification based on ScaleWide Area Network (WAN)
Provides long-distance transmission of data, voice, imageand information over large geographical areas that maycomprise a country, continent or even the whole world
May utilize public, leased or private communication devices
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Classification based on ScaleWide Area Network (WAN)
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Classification based on ScaleInternet
A network that interconnects hundreds of millions ofcomputing devices (hosts or end systems)
Traditionally desktop PCs, Linux workstations, and servers
Nontraditionally laptops, smartphones, tablets, TVs, gamingconsoles, Web cams, automobiles, environmental sensingdevices, picture frames, and home electrical & securitysystems
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Internet
Connected together by a network of
Communication Links: Different types of physical media,including coaxial cable, copper wire, optical fiber, and radiospectrum
Packet Switch: Takes a packet arriving on one of its incomingcommunication links and forwards that packet on one of itsoutgoing communication links
Sequence of communication links and packet switchestraversed by a packet from the sending end system to thereceiving end system is known as a route or path through thenetwork
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Internet
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InternetInternet Service Providers
End systems access the Internet through Internet ServiceProviders (ISPs)
Residential ISPs such as local cable or telephone companiesCorporate ISPsUniversity ISPs; andISPs that provide WiFi access in airports, hotels, coffee shops,and other public places
Each ISP is in itself a network of packet switches andcommunication links providing
Residential broadband access such as cable modem or DSLand 56 kbps dial-up modem accessHigh-speed LAN access, wireless accessInternet access to content providers, connecting Web sitesdirectly to the Internet
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InternetA Services Description
An infrastructure that provides services to applications
Electronic mailWeb surfingSocial networksInstant messagingVoice-over-IP (VoIP)Video streaming
Distributed gamesPeer-to-peer (P2P) filesharingTelevision over the InternetRemote login, and . . .
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InternetA Services Description
Applications are called Distributed Applications as theyinvolve multiple end systems that exchange data with eachother
Connection-oriented service: guarantees that datatransmitted from a sender to a receiver will eventually bedelivered to the receiver in-order and in its entiretyConnectionless service: does not make any guaranteesabout eventual delivery
An infrastructure in which new applications are beingconstantly invented and deployed
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Internet Usage in the World
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Internet Usage in the World
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ProtocolHuman Anology
Human Protocol
Specific messages wesend, and specific actionswe take in response to thereceived reply messagesor other events (such asno reply within somegiven amount of time)
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ProtocolNetwork Anology
Network Protocol
Defines the format andthe order of messagesexchanged between twoor more communicatingentities, as well as theactions taken on thetransmission and/orreceipt of a message
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Network Functions
Information Transmission
To transfer information between a source and a destination
Communication may involve
Transfer of a single block of information
Transfer of a stream of information between nodes
Information storageVoice data
Text
Figures
Multimedia data and potential new kind of data
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Network Functions
Information processing
Various computing techniques to meet the continuingrequirements for network users
Users can execute complex applications and obtain servicefrom ubiquitous networks
Can work as a virtual society of real-life world such as:
Virtual university (education)
Virtual game environment
Virtual social networks, etc.
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Network Functions
Network Management
The network operation must ensure that network resources areused effectively under normal as well as under problemconditions
Traffic controls are necessary to ensure the smooth flow ofinformation through the network
It includes:
Monitoring the performance of the network
Detecting and recovering from faults
Configuring the network resources
Maintaining accounting information for cost and billing
Providing security by controlling access to the information flowsin the network
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Future of Networks
Moore’s LawThe processing power of a microchip doubles every 18months; corollary, computers become faster and the price of agiven level of computing power halves every 18 months
Gilder’s LawThe total bandwidth of communication systems triples everytwelve months for the next 25 years
Bandwidth grows at least three times faster than computerpower
Cost per communication bit will begin to sink farther than it hasfallen previously and eventually the cost of a telephone call, orof a bit transmitted, will be “free”
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Future of Networks
Metcalfe’s Law
Value of a telecommunicationsnetwork is proportional to thesquare of the number of connectedusers of the system (n2)