This document defines key data communication terminology like session, network, node, link, path, circuit, and packetizing. It describes different data flow types including simplex, half-duplex, and full-duplex transmission modes. Networks are introduced as interconnected groups of devices that allow sharing of information and resources. Distributed processing and important network criteria like performance, reliability, and security are also outlined. The physical structures of networks include type of connection, either point-to-point or multipoint, and topology.

1. DATA
COMMUNICATION
LeCTUre-2LeCTUre-2

2. reCAp Of LeCTUre 1reCAp Of LeCTUre 1
• DataCommunication
• DataCommunication System
• Factorseffecting DataCommunication system
• Componentsof datacommunication system
• DataRepresentation

3. OvervIew Of LeCTUre 2OvervIew Of LeCTUre 2
• Key DataCommunication Terminology
• DataFlow types
• Networksand Why weneed Them?
• Distributed Processing
• Network Criteria
• Physical structureof Network
• Typeof connection

4. Key DATA COMMUNICATIONKey DATA COMMUNICATION
TerMINOLOgyTerMINOLOgy
Session
Communication dialog between network usersor applications.
Network
Interconnected group of computersand communication devices.
Node
Any devicethat ispart of network.
Any device that is capable of sending or receiving data (e.g. computer, printer
etc.)
Link
connectsadjacent nodes.
e.g. Wires, Cables, any thing that physically connects two nodes, or it
can bewireless.

5. Key DATAKey DATA
COMMUNICATIONCOMMUNICATION
TerMINOLOgyTerMINOLOgy
Path
end-to-end routewithin anetwork.
Circuit
theconduit or physical path over which datatravels.
Packetizing
Dividing messages into fixed-length packets prior to
transmission over anetwork’scommunication media.
Routing
Determining a message’s path from sending to receiving
nodes.

6. DATA fLOw / TrANsMIssIONDATA fLOw / TrANsMIssION
MODeMODe
Communication between two devicescan be;
1. Simplex
2. Half-duplex
3. Full-duplex

7. sIMpLexsIMpLex
• Communication takeplaceonly in onedirection.
 Only sender just sendsdata& receiver just receivedata.
 The simplex mode can use the entire capacity of the channel to
send datain onedirection.
 Called asone-way transmission
 i.e. there is no back direction of transmission from receiver to
sender
 e.g.
 Radio, TV transmission.
 Input provided to the computer by keyboard, mouse, or scanner
etc.
 Theflow of datafrom thecomputer to monitor, and printer etc.

8. sIMpLexsIMpLex

9. Half-DuplexHalf-Duplex
• Each station can both transmit and receive, but not at the same
time.
• When one device is sending, the other can only receive, and
viceversa
• the entire capacity of a channel is taken over by whichever of
thetwo devicesistransmitting at thetime.
• e.g.
 wirelesssystem
 walky-talky
 In computer field a multi-user environment is a best example of
half duplex mode, in which a terminal transmits data to main
computer and then thecomputer respondswith acknowledgment.

10. Half-DuplexHalf-Duplex

11. full Duplexfull Duplex
• Two-way transmission.
• Both sender and receiver transmit datasimultaneously.
• Signalsgoing in either direction sharethecapacity of thelink.
• Thissharing can occur in two ways:
• Either thelink must contain two physically separatetransmission paths
• Or the capacity of the channel is divided between signals
traveling in both directions.
• The best example is telephone communication. Similarly
modem card, NIC, sound card etc are the devices used in
computer technology for full duplex transmission.

12. full Duplexfull Duplex

13. NetworksNetworks

14. NetworksNetworks
• When two or more Devices (Nodes) are connected through a
medium (e.g. cable) to sharetheir resourcesand information, it
iscalled anetwork”.
• A node can beacomputer, printer, or any other devicecapable
of sending and/or receiving data generated by other nodes on
thenetwork.
• In other words, a group of computers and other devices
connected together is called computer network, and this
processiscalled computer networking.

15. Networks- wHy we NeeDNetworks- wHy we NeeD
tHem?tHem?
• Point to point communication not usually practical
 Devicesaretoo far apart.
 Largeset of deviceswould need impractical number of connections.
• Solution is to connect all devices to a central system known as a
NETWORK

16. BeNefits of NetworkiNgBeNefits of NetworkiNg
• Sharing of information.
 e.g. sharing information in businessenvironment
• Sharing thehardwareresources.
 E.g. Printer, modem, scanner, hard disk, CDRom, floppy disc,
plotter etc.
• Sharing SoftwareResources.
 MSOfficeand Lotsof application software.
• Preserving theinformation.
 Centralized backup.
• Protecting theinformation.
 By applying authentication schemes.
• E-mail
 peopleto communicate.

17. DistributeD ProcessingDistributeD Processing
• “Instead of a single large machine being responsible for all
aspects of a process, each separate computer handles a subset
of thetask”
• Most networks use distributed processing, in which a task is
divided among multiplecomputers.

18. network criterianetwork criteria
Data Communication
Network Criteria
Performance Reliability Security

19. network criterianetwork criteria
1. Performance
• Can be measured in many ways including Transit and
Responsetime.
• Transit time is the amount of time required for a message to
travel from onedeviceto another.
• Response time is the elapsed time between an inquiry and a
response.
• Performancedependsupon thesefactors
1. Number of Users
2. Typeof Transmission Medium
3. Capabilitiesof Hardware
4. Efficiency of Software

20. network criterianetwork criteria
2. Reliability
• Dependsupon ano. of factors
• Frequency of failure
• Recovery Timeof anetwork after Failure
• Network'srobustnessin acatastrophe.
• E.g. Fireearthquakeor theft

21. network criterianetwork criteria
3. Security
• Issuesinclude;
• Protecting datafrom unauthorized access,
• Protecting datafrom damage,
• and implementing policies and procedures
for recovery from breachesand datalosses.

22. Physical structures ofPhysical structures of
networknetwork
1. Typeof Connection
2. Topology

23. Physical structuresPhysical structures
• Type of Connection
• Also refer asLineConfiguration.
• “Line Configuration refers to the way two or more devices
attach to alink”
• In a network two or more devices are connected through
links.
• A link is a communications pathway that transfers data
from onedeviceto another.
• For communication to occur, two devices must be
connected in someway to thesamelink at thesametime.
• Therearetwo possibletypesof connections:
• point-to-point
• and multipoint.

24. line configurationline configuration
Spatially Shared Time Shared
MultipointPoint-to-Point
Line Configuration

25. Point-to-PointPoint-to-Point
• A point-to-point connection provides a dedicated link
between two devices.
• The entire capacity/bandwidth of the link is reserved for
transmission between thosetwo devices.
• Most point-to-point connections use an actual length of
wire or cable to connect the two ends, but other options,
such asmicrowaveor satellitelinks, arealso possible.
• Data and control information pass directly between
entitieswith no intervening agent.
• e.g. TV Remote Control, mobile phone when talking, Base
station (Antenna)

26. Point-to-Point LinePoint-to-Point Line
ConfigurationConfiguration

27. MuLtiPointMuLtiPoint
• A multipoint (also called multi-drop) connection
is one in which more than two specific devices
shareasinglelink.
• Capacity (bandwidth) of thelink isshared.
• Spatial sharing
• Multipledevicessharethelink simultaneously.
• Temporal (Time) sharing
• User usesthelink only at their timeslot.

28. MuLtiPoint LineMuLtiPoint Line
ConfigurationConfiguration

29. SuMMarySuMMary
• Key DataCommunication Terminology
• DataFlow types/ Transmission Modes
• Networksand Why weneed Them?
• Distributed Processing
• Network Criteria
• Physical structureof Network
• Typeof connection

30. SuggeSted readingSuggeSted reading
 Section
 1.1,
 1.2,
 “Data Communications and Networking” 4th
Edition by Behrouz
A. Forouzan
 Sections
 1.3,
 “Data and Computer Communication” 6th Edition by William
Stallings