introduction to data communications and computer networks
TRANSCRIPT
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Introduction to Data Communications and Computer Networks
Chaiporn Jaikaeo
Department of Computer EngineeringKasetsart University
01204325 Data Communications and Computer Networks
Based on lecture slides by Assoc.Prof.Surasak Sanguanpong
Revised 2020-07-14
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Outline•Communications Model•Basic Data Communication Terminology•Protocols and Standards Organizations
•Networking• The Internet
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Telecom vs. Datacom• Communications
◦ Transfer of data from one entity to another via some form of transmission medium
• Telecommunications◦ Communication over a distance by definition◦ All type of communications using signaling such as
voice (telephone), images (television), data (computers)
• Data communications◦ Subset of telecommunications that involves the
transmission and reception of data to and from computers and components of computer systems
Image by Pezibear, Alexas_Fotos, and Michael Schwarzenberger from Pixabay
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Communication Model
input message
communications system
source system destination system
source device
transmitter transmissionmedium receiver
destination device
input data
transmitted signal
received signal
output data
output message
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Example of Communication System
Telephone Network
source system destination systemA
110011 110011
A
computer
modem modem
computer
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Components of Data Communications
message
communication system
source system destination system
source device
transmitter transmissionmedium receiver
destination device
input data
transmitted signal
received signal
output data
message
1 2
3
4
5 protocol
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Protocols and Standards•Protocol
◦ A set of rules governing data communications◦ Syntax: format of data block◦ Semantics: meaning of each section◦ Timing: speed and sequencing◦ etc.
•Standard◦ De facto (in practice) standards
◦ ® not approved but widely adopted
◦ De jure (in law) standards◦ ® approved by an organization
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Examples of Standards OrganizationslList of some major standard bodies
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ITU-T
• International standard organization that develops standard for telecommunications• Some well known standards
◦ V series◦ X series◦ H series◦ G Series
International Telecommunications Union –Telecommunication Standard Sector
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ISO
•An International standard organization that develops standard for variety of fields
International Standards Organization
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IETF
•A large open international community of network designers, operators, vendors, and researchers concerned with the evolution of the Internet architecture
Internet Engineering Task Force
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IEEE
• The largest professional group involved in standards for computing, communications, electrical and electronics
Institute of Electrical and Electronics Engineers
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Networks•A network is a set of two or more devices connected
through a communication system
Communication System
Cliparts are taken from http://openclipart.org
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Line Configurations
Point-to-Point
Multipoint
Line configurations
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Point-to-Point Connection•Only two devices share the medium• The entire capacity of the link is reserved for the
transmission between those two devices
Station Station
A direct link between two devices
A direct link between two devices
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Multipoint Connection•More than two devices share the same medium• The capacity of the link is shared
StationStation
A link is sharedbetween several devices
StationStation Station
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Direction of Data Flow
Simplex
Half-duplexType of Direction
Full-duplex
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Simplex
Unidirectional
Computer Display
Hi….
TelevisionBroadcast station
•Data are only transmitted in one direction•One device can only transmit; the other can only receive
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Half-duplex•Both stations may transmit; but only one at a time
(alternate in transmitting)• Example: Walkie-Talkies
Transmit from S1 to S2 at time T1
Transmitter/ReceiverTransmitter/Receiver Transmit from S2 to S1 at time T2
S2S1
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Full-duplex• Full-Duplex operation can occur in two ways:
◦ two separate transmission path◦ channel is divided between signals traveling in opposite directions
• Example: telephones
Simulteneous send and receive data from each other
Transmitter/ReceiverTransmitter/Receiver
S2S1
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Data Transmission
Parallel
Serial
Asynchronous
Data Transmission
Synchronous
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Parallel Transmission• Simultaneous transmission results in high speed•Required more data lines, hence higher cost•Usually limited to short distances because its costs and
crosstalk
Need eight data lines for sending each byte
0
1
0
1
1
0
1
1
https://en.wikipedia.org/wiki/Parallel_port#/media/File:Parallel_computer_printer_port.jpg
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Serial Transmission•One bit follows another, only one data line for each
direction• The sender needs a parallel-to-serial converter and the
receiver needs a serial-to-parallel converter.
Need only one data line
0101101110 0100101110 0000101110 0110101110
A group of bits are sent one after another
https://en.wikipedia.org/wiki/USB#/media/File:Usb_head_Cable.jpg
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Network Topologies•Common topologies are bus, ring, star, and mesh
Network Topologies
Bus
Ring
Star
Mesh
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Switching Technologies•Circuit switching
◦ A circuit is established for the two parties
•Packet switching◦ Data are put into packets, each
stamped with source and destinationaddresses
◦ Routers know where to forward packets
telephoneswitch
RouterPacket
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Network Categories by Distance
Network categories(by distance)
Local Area Network(LAN)
Metropolitan Area Network(MAN)
Wide Area Network(WAN)
Body/Personal Area Network(BAN/PAN)
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LAN – Local Area Networkhub/switch
hub/switch
hub/switch
hub/switchrouter
General Characteristics :
l Confined geographical areal Under single managementl High data rate
servers
stations
stations
stations
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MAN – Metropolitan Area Network•A network which cover an entire city•A single network or a number of connected LANs
Public city network
LANLAN
LANLAN
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WAN – Wide Area Network•A network that covers a relatively broad geographic area• It often uses long-distance transmission facilities provided
by public carriers
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BAN/PAN – Body/Personal Area Network
http://developer.sonymobile.com
Nike.com
https://www.bhphotovideo.com/images/images1000x1000/Adesso_IMOUSE_S100_Bluetooth_Mini_Optical_Scroll_696816.jpg
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Network of Networks
Company A
Company D
Network Interface Card (NIC)
Company B
Company C
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Internetworking• How to allow devices of different standards to communicate?
• Gateways/routers – devices capable of communicating in several standards
• These become "network of networks", i.e., internetwork
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Internetworks•Collection of networks interconnected by routers and
other devices
LAN
LAN
LAN
LAN
MAN
WAN
LAN
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The Internet• The largest internetwork in the world•Devices communicating with TCP/IP protocol suite
UCLA
Stanford
UC Santa Barbara
U. of Utah
Early ARPANET nodes in 1969
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Internet Growth
https://devcentral.f5.com/articles/security-sidebar-defending-the-internet-of-things
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Technologies Around Us•New generation of switching technologies provide
improved services to home and workplace
Frame RelayNetwork
ATMNetwork
ISDNNetwork
E/T-carrier
Cable ModemADSL CATV
PSTNNetwork
Modem
Cellular3G/4G/5G
Internet
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Summary•Data communications
◦ Protocols and standards◦ Data flows◦ Connectivity
•Computer networks◦ Topologies◦ LAN/MAN/WAN/BAN/PAN
• Internetworks (networks of networks)• The Internet