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Data Communication & NetworkingData Communication & Networking
IntroductionIntroduction
Data Communication & Networking are changing the way we do business and the way we live.
For better business decision we require immediate access to accurate information.
Technological advances are making it possible for communication links to carry more & faster signals.
When we communicate we share information, this sharing can be local or remote.
The term telecommunication which includes telephony, telegraphy & television means communication at a distance (Tele is Greek for “far”)
Data CommunicationsData Communications
DataData Information presented in whatever form is agreed upon by the Information presented in whatever form is agreed upon by the
parties creating and using the dataparties creating and using the data Data communicationData communication
Exchange of data between two devicesExchange of data between two devices Via some form of transmission medium such as wire cableVia some form of transmission medium such as wire cable
Fundamental characteristics of data communicationFundamental characteristics of data communication Delivery : System must deliver the data to the correct Delivery : System must deliver the data to the correct
destination.destination. Accuracy: System must deliver the data accurately. Accuracy: System must deliver the data accurately. Timeliness:Timeliness: Jitter: Refer to the Variation in the packet arrival time For Ex Jitter: Refer to the Variation in the packet arrival time For Ex
assume that video packet are sent every 30 ms. If some of the assume that video packet are sent every 30 ms. If some of the pocket arrive with 30 ms delay and others with 40 ms delay, an pocket arrive with 30 ms delay and others with 40 ms delay, an uneven quality in the video is the resultuneven quality in the video is the result.. ..
Five Components of Data Five Components of Data CommunicationCommunication
Five Components of Data Five Components of Data CommunicationCommunication
Message: Information(data) to be communicatedMessage: Information(data) to be communicated
Sender : Device that sends the data message. It can be computer, telephone handset, Sender : Device that sends the data message. It can be computer, telephone handset,
video camera & so onvideo camera & so on
Receiver: That receive the message . It can be computer, telephone handset, video Receiver: That receive the message . It can be computer, telephone handset, video
camera & so on camera & so on
Transmission medium: Physical path by which a message travels. Ex. Twisted pair, Transmission medium: Physical path by which a message travels. Ex. Twisted pair,
coaxial cable, fiber-optical cable, radio waves. coaxial cable, fiber-optical cable, radio waves.
Protocol: A set of rules that govern data communication without a protocol device may be Protocol: A set of rules that govern data communication without a protocol device may be
connected but not communicating, just as speaking French cannot be understand by a connected but not communicating, just as speaking French cannot be understand by a
person who speak only Japanese person who speak only Japanese
Direction of Data FlowDirection of Data Flow
Data FlowData Flow SimplexSimplex
UnidirectionalUnidirectional As on a one-way streetAs on a one-way street Ex: Keyboard, MonitorEx: Keyboard, Monitor
Half-duplexHalf-duplex Both transmit and receive possible, but not at the same timeBoth transmit and receive possible, but not at the same time Like a one-lane road with two-directional trafficLike a one-lane road with two-directional traffic Walkie-talkieWalkie-talkie
Full-duplex (Duplex)Full-duplex (Duplex) Transmit and receive simultaneouslyTransmit and receive simultaneously Like a two-way street, telephone networkLike a two-way street, telephone network Channel capacity must be divided between two directionsChannel capacity must be divided between two directions
NetworkNetwork
Network: A set of devices (nodes) connected by communication linksNetwork: A set of devices (nodes) connected by communication links Node: Computer, printer, or any device capable of sending and/or Node: Computer, printer, or any device capable of sending and/or
receiving datareceiving data To be considered effective and efficient, a network must meet a To be considered effective and efficient, a network must meet a
number of criterianumber of criteria
NetworkNetwork Performance : can be measure by transit time & Response time.Performance : can be measure by transit time & Response time.
Transit time is the amount of time required for a message to travel from one device to Transit time is the amount of time required for a message to travel from one device to
another.another.
Response Time: is the elapsed time between an inquiry and response.Response Time: is the elapsed time between an inquiry and response.
Performance depends up number of users ,types of transmission medium, capacity of Performance depends up number of users ,types of transmission medium, capacity of
hardware, efficiency of the softwarehardware, efficiency of the software
Performance also evaluated using Performance also evaluated using Throughput and DelayThroughput and Delay
Network throughput is the average rate of successful message delivery over a Network throughput is the average rate of successful message delivery over a
communication channel.communication channel. The throughput is usually measured in The throughput is usually measured in bits per second (bit/s per second (bit/s
or bps), and sometimes in or bps), and sometimes in data packets per second or data packets per per second or data packets per time slot. .
NetworkNetwork
Reliability : can be measure frequency of failure, the time it takes a Reliability : can be measure frequency of failure, the time it takes a
link to recover from failure.link to recover from failure.
Security: It include protecting data from unauthorized access, Security: It include protecting data from unauthorized access,
protecting data from damage and development and implementing protecting data from damage and development and implementing
policies and procedures for recovery from breaches and data policies and procedures for recovery from breaches and data
losses.losses.
Uses of Computer NetworksUses of Computer Networks
Business ApplicationsBusiness Applications Home ApplicationsHome Applications Mobile UsersMobile Users Social IssuesSocial Issues
Uses of Computer NetworksUses of Computer NetworksBusiness ApplicationsBusiness Applications Many companies have a substantial number of Many companies have a substantial number of
computerscomputers the issue here is resource sharing, and the goal the issue here is resource sharing, and the goal
is to make all programs, equipment, and is to make all programs, equipment, and especially data available to anyone on the especially data available to anyone on the network without regard to the physical location network without regard to the physical location of the resource and the user. of the resource and the user.
An example is having a group of office workers An example is having a group of office workers share a common printer, scanners, and CD share a common printer, scanners, and CD burnersburners
more important, is sharing informationmore important, is sharing information
Uses of Computer NetworksUses of Computer NetworksBusiness ApplicationsBusiness Applications Most companies have customer records, Most companies have customer records,
inventories, accounts receivable, financial inventories, accounts receivable, financial statements, tax information, and much more statements, tax information, and much more online.online.
If all of its computers went down, a bank could If all of its computers went down, a bank could not last more than five minutes. A modern not last more than five minutes. A modern manufacturing plant, with a computer-controlled manufacturing plant, with a computer-controlled assembly line, would not last even that long. Even assembly line, would not last even that long. Even a small travel agency or three-person law firm is a small travel agency or three-person law firm is now highly dependent on computer networks for now highly dependent on computer networks for allowing employees to access relevant information allowing employees to access relevant information and documents instantly.and documents instantly.
Uses of Computer NetworksUses of Computer NetworksBusiness ApplicationsBusiness Applications Most companies have customer records, Most companies have customer records,
inventories, accounts receivable, financial inventories, accounts receivable, financial statements, tax information, and much more statements, tax information, and much more online.online.
If all of its computers went down, a bank could If all of its computers went down, a bank could not last more than five minutes. A modern not last more than five minutes. A modern manufacturing plant, with a computer-controlled manufacturing plant, with a computer-controlled assembly line, would not last even that long. Even assembly line, would not last even that long. Even a small travel agency or three-person law firm is a small travel agency or three-person law firm is now highly dependent on computer networks for now highly dependent on computer networks for allowing employees to access relevant information allowing employees to access relevant information and documents instantly.and documents instantly.
Business Applications of Business Applications of NetworksNetworks
A network with two clients and one server.A network with two clients and one server.
Business Applications of Networks Business Applications of Networks as Communication Mediumas Communication Medium
A computer network can provide a powerful communication medium among employees.
Virtually every company that has two or more computers now has e-mail (electronic mail)
Yet another form of computer-assisted communication is videoconferencing
A third goal for increasingly many companies is doing business electronically with other companies
A fourth goal that is starting to become more important is doing business with consumers over the Internet. Called e-commerce
Business Applications of Business Applications of Networks as Communication Networks as Communication
MediumMedium The client-server model involves requests The client-server model involves requests
and replies.and replies.
Home Network ApplicationsHome Network Applications
• Access to remote informationAccess to remote information• It can be surfing the World Wide Web for It can be surfing the World Wide Web for
information or just for fun. information or just for fun. • Information available includes the arts, Information available includes the arts,
business, cooking, government, health, business, cooking, government, health, history, hobbies, recreation, science, sports, history, hobbies, recreation, science, sports, travel, and many others.travel, and many others...
• Person-to-person communicationPerson-to-person communication• Interactive entertainmentInteractive entertainment• Electronic commerceElectronic commerce
Home Network ApplicationsHome Network Applications
• Person-to-person communicationPerson-to-person communication• instant messaging, chat roominstant messaging, chat room• peer-to-peer communication-In this peer-to-peer communication-In this
form, individuals who form a loose form, individuals who form a loose group can communicate with others in group can communicate with others in the groupthe group
• Interactive entertainmentInteractive entertainment• Electronic commerceElectronic commerce
Home Network Applications Home Network Applications (2)(2)
In peer-to-peer system there are no fixed In peer-to-peer system there are no fixed clients and servers.clients and servers.
Home Network Applications Home Network Applications (3)(3)
Some forms of e-commerce.Some forms of e-commerce.
Type of ConnectionType of Connection A network is two or more devices connected through link. A A network is two or more devices connected through link. A
link is communication pathway that transfer data from one link is communication pathway that transfer data from one device to another. Two types connectiondevice to another. Two types connection
Point-to-pointPoint-to-point Dedicated link between two devicesDedicated link between two devices The entire capacity of the channel is reservedThe entire capacity of the channel is reserved Ex) Microwave link, TV remote control Ex) Microwave link, TV remote control
Multipoint also called Multidrop Multipoint also called Multidrop More than two devices share a single linkMore than two devices share a single link Capacity of the channel is eitherCapacity of the channel is either
• Spatially sharedSpatially shared: Several Devices can use the link : Several Devices can use the link simultaneouslysimultaneously
• TimeshareTimeshare: Users take turns: Users take turns
Type of ConnectionType of Connection
Physical TopologyPhysical Topology It refers to the way in which a network is laid out It refers to the way in which a network is laid out
physically.physically. Two or more devices connect to a link; two or more link Two or more devices connect to a link; two or more link
form a topology.form a topology. The topology of a network is the geometric The topology of a network is the geometric
representation of the relationship of all the links and representation of the relationship of all the links and linking device to one another.linking device to one another.
Four basic topologies: Mesh, Star, Bus, RingFour basic topologies: Mesh, Star, Bus, Ring
Mesh TopologyMesh Topology
Mesh TopologyMesh Topology Every device has a dedicated point-to-point link to every other device.Every device has a dedicated point-to-point link to every other device.
To find the number of physical link in a fully connected mesh network To find the number of physical link in a fully connected mesh network
with n nodes.with n nodes.
Each nodes must be connected to every other nodes. Nodes 1 must be Each nodes must be connected to every other nodes. Nodes 1 must be
connected to n-1 nodes, nodes 2 connected to n-1 and finally node n connected to n-1 nodes, nodes 2 connected to n-1 and finally node n
must connected to n-1 nodes.must connected to n-1 nodes.
We need n(n-1) physical link.We need n(n-1) physical link.
However if each physical link allows communication in both direction However if each physical link allows communication in both direction
we can divide the number of link by 2 we can divide the number of link by 2
A mesh network with A mesh network with nn nodes has nodes has n(n-1)/2n(n-1)/2 links. links.
Mesh TopologyMesh Topology Advantages:Advantages:
Use of dedicated links guarantees that each connection can carry its own data Use of dedicated links guarantees that each connection can carry its own data
load. Thus no traffic problems, load. Thus no traffic problems,
Robust If one link become unusable, it does not incapacitate the entire system.Robust If one link become unusable, it does not incapacitate the entire system.
Security, only intended recipient see the message Security, only intended recipient see the message
Easy fault identificationEasy fault identification & isolation & isolation
Disadvantages:Disadvantages:
Amount of cabling and the number of port required. Amount of cabling and the number of port required.
Every device must be connected to every device therefore difficult Every device must be connected to every device therefore difficult
installation/reconfiguration, space, costinstallation/reconfiguration, space, cost
Star TopologyStar Topology Dedicated point-to-point link Dedicated point-to-point link only toonly to a central controller, called a a central controller, called a hubhub Devices are not directly linked to one another. Devices are not directly linked to one another. Hub acts as an exchange: No direct traffic between devicesHub acts as an exchange: No direct traffic between devices Advantages: Less expensive, robust, easy to install and reconfigureAdvantages: Less expensive, robust, easy to install and reconfigure Disadvantages: dependency of the whole on one single point, the hubDisadvantages: dependency of the whole on one single point, the hub Example LAN Example LAN
Bus TopologyBus Topology One long cable that links all nodesOne long cable that links all nodes Nodes are connected to the bus cable by tap and drop line Nodes are connected to the bus cable by tap and drop line As signal travels along the backbone some of its energy is transferred into heat. As signal travels along the backbone some of its energy is transferred into heat.
Therefore there is limit on the number taps a bus can support and on the distance Therefore there is limit on the number taps a bus can support and on the distance between those tapsbetween those taps
Advantages: Easy installation, cheapAdvantages: Easy installation, cheap Disadvantages: Difficult reconfiguration, no fault isolation, a fault or break in the bus Disadvantages: Difficult reconfiguration, no fault isolation, a fault or break in the bus
stops all transmissionstops all transmission
Ring TopologyRing Topology Dedicated point-to-point link only with the two nodes on each sidesDedicated point-to-point link only with the two nodes on each sides A signal is passed along the ring in one direction, from device to device, A signal is passed along the ring in one direction, from device to device,
until it reaches its destination.until it reaches its destination. Each device in the ring incorporate a repeater.Each device in the ring incorporate a repeater. Advantages: Easy reconfiguration, fault isolationAdvantages: Easy reconfiguration, fault isolation Disadvantage: Unidirectional traffic, a break in the ring cab disable the Disadvantage: Unidirectional traffic, a break in the ring cab disable the
entire networkentire network
Hybrid TopologyHybrid Topology Example: Main star topology with each branch connecting several stations in Example: Main star topology with each branch connecting several stations in
a bus topologya bus topology To share the advantages from various topologiesTo share the advantages from various topologies
Hybrid TopologyHybrid Topology
Categories of NetworksCategories of Networks
LANLAN Usually privately ownedUsually privately owned A network for a single office, building, or campus A network for a single office, building, or campus a few Km a few Km Common LAN topologies: bus, ring, starCommon LAN topologies: bus, ring, star An isolated LAN connecting 12 computers to a hub in a closetAn isolated LAN connecting 12 computers to a hub in a closet
MANMAN Designed to extend to an entire cityDesigned to extend to an entire city Cable TV network, a company’s connected LANsCable TV network, a company’s connected LANs Owned by a private or a public companyOwned by a private or a public company
WANWAN Long distance transmission, e.g., a country, a continent, the worldLong distance transmission, e.g., a country, a continent, the world Enterprise network: A WAN that is owned and used by one companyEnterprise network: A WAN that is owned and used by one company
Wired Network Transmission MediaWired Network Transmission Media Twisted-pair cable Twisted-pair cable
Pairs of wires twisted togetherPairs of wires twisted together Used for telephone and network Used for telephone and network
connectionsconnections Coaxial cableCoaxial cable
Thick center wireThick center wire Used for computer networks, short-run Used for computer networks, short-run
telephone transmissions, cable television telephone transmissions, cable television deliverydelivery
Fiber-optic cableFiber-optic cable Glass or fiber strands through which light Glass or fiber strands through which light
can passcan pass Used for high-speed communicationsUsed for high-speed communications
Wired Network Transmission MediaWired Network Transmission Media
InternetworkInternetwork
Internetwork (internet) : two or more networks are Internetwork (internet) : two or more networks are connected by internetworking devicesconnected by internetworking devices
Internetworking devices: router, gateway, etc.Internetworking devices: router, gateway, etc. The Internet: a specific worldwide networkThe Internet: a specific worldwide network
The InternetThe Internet The Internet has revolutionized many aspects of our daily lives. It The Internet has revolutionized many aspects of our daily lives. It
has affected the way we do business as well as the way we has affected the way we do business as well as the way we
spend our leisure time. The Internet is a communication system spend our leisure time. The Internet is a communication system
that has brought a wealth of information to our fingertips and that has brought a wealth of information to our fingertips and
organized it for our use.organized it for our use.
1967: ARPANET proposed by DoD’s ARPA(Advanced Research Project 1967: ARPANET proposed by DoD’s ARPA(Advanced Research Project
Agency)Agency)
1969: ARPANET in a reality: UCLA, UCSB, SRI, U. of Utah1969: ARPANET in a reality: UCLA, UCSB, SRI, U. of Utah
1973: Vint Cerf and Bob Kahn propose TCP, 1973: Vint Cerf and Bob Kahn propose TCP,
To split TCP into two protocols TCP and IPTo split TCP into two protocols TCP and IP
Internet Internet TodayToday
• ISP (Internet service providers)
• NISP (national ISP)
• NAP (network access point)
ProtocolsProtocols Protocol : ruleProtocol : rule
A set of rules that govern data communicationA set of rules that govern data communication For communication to occur, entities must agree upon a protocolFor communication to occur, entities must agree upon a protocol A protocol define what is communicated, how it is A protocol define what is communicated, how it is
communicated, and when it is communicatedcommunicated, and when it is communicated.. Key elements of a protocolKey elements of a protocol
Syntax: structure or format of dataSyntax: structure or format of data Semantics: meaning of each section of bits. How is a particular Semantics: meaning of each section of bits. How is a particular
pattern to be interpreted,& what action is to be taken based on pattern to be interpreted,& what action is to be taken based on that interpretation?.that interpretation?.
Timing: Timing: whenwhen and and how fasthow fast data should be sent data should be sent
Standards: agreed-upon rulesStandards: agreed-upon rules Standards is essential inStandards is essential in
Creating/maintaining open and competitive markets for equipment Creating/maintaining open and competitive markets for equipment
manufacturersmanufacturers
Guaranteeing national/international interoperability of data & technologyGuaranteeing national/international interoperability of data & technology
Two categoriesTwo categories
De jure (“by law” or “by regulation’) standardsDe jure (“by law” or “by regulation’) standards
De facto (“by fact” or ‘by convention’) standardsDe facto (“by fact” or ‘by convention’) standards
• Proprietary standards: closed standardsProprietary standards: closed standards
• Nonproprietary standards: open standardsNonproprietary standards: open standards
Standards OrganizationsStandards Organizations Standards are developed byStandards are developed by
Standards creation committeesStandards creation committees ForumsForums Regulatory agenciesRegulatory agencies
Standards committees & forumsStandards committees & forums Standards committees are slow movingStandards committees are slow moving Forums are made up of interested corporationsForums are made up of interested corporations Forum are able to speed acceptance of a Forum are able to speed acceptance of a
particular technologyparticular technology
Standards CommitteesStandards Committees
ISO( International Organisation for Standardization)ISO( International Organisation for Standardization) Voluntary international organization Voluntary international organization
ITU-T ( International Telecommunication Union- ITU-T ( International Telecommunication Union- Telecommunication standards SectorTelecommunication standards Sector
Formerly, CCITT (Consultative Committee for International Formerly, CCITT (Consultative Committee for International Telegraphy & Telephony formed by UNTelegraphy & Telephony formed by UN
ANSI ( American National Standards Institute)ANSI ( American National Standards Institute) Private non-profit corporation in the USPrivate non-profit corporation in the US
IEEE( Institute of electrical & electronic engg.)IEEE( Institute of electrical & electronic engg.) The largest engineering society in the worldThe largest engineering society in the world
EIA( electronic Industries AssociationEIA( electronic Industries Association Non-profit organization in the USNon-profit organization in the US
Internet StandardsInternet Standards
IETF (Internet Engineering Task Force)IETF (Internet Engineering Task Force) Internet DraftInternet Draft
working document with no official statusworking document with no official status with a 6-month lifetimewith a 6-month lifetime
RFC (Request for Comment)RFC (Request for Comment) Edited, assigned a number, and made Edited, assigned a number, and made
available to all interested partiesavailable to all interested parties