Computer Network

1. Chapter 4
SC161: Principles of Information Technology
Communication and Network
Part 2: Computer Network
Thiti Theerathean
Center for Teaching Excellence
University of the Thai Chamber of Commerce
E-mail : thiti_the@utcc.ac.th

2. 2
• Introduction to Computer Network.
- Types of Computer Network.
- The basic Configurationsof Computer Network.
- The Benefits of Computer Network.
• Network Architecture Model.
- OSI Model.
- InternetModel.
• Local Area Network.
- The Components of LAN.
- Topologies of LAN.
• Wide Area Network.
- TransmissionFacility.
- Modulation.
- Multiplexing.
SC161: Principlesof Information Technology

3. 3SC161: Principlesof Information Technology
A Computer network is an interconnection of computers and computing equipment using
either wire and wireless over small or large geographic areas.
Twisted pair, Radio wave
Coaxial, Fiber Optic
Fiber Optic, Microwave

4. 4SC161: Principlesof Information Technology
Personal Area Network : PAN
A personal area network is a computer network organized around an individual person.
PANs typically involve a mobile computer, a cell phone or a handheld computing device such
as a PDA.
Bluetooth PANs are also called piconet.

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The Big Picture of Computer Network.

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The Basic Configurations of Computer Network.
PCs to LAN
LAN to LANs

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The Basic Configurations of Computer Network.
PC to WAN
LAN to WAN

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The Benefits of Computer Network
People and Organizations use networks for the following reason, the most important of
which is the sharing of resource.
• Resource sharing
• Data and information sharing
• Better Communications
• Reduced Cost
• On-line services
• Electronic data interchange

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10. 10SC161: Principlesof Information Technology
How do you sends a message to your friends ?
Message.
Department.
Company.
POST Code.
Country.
Thiti Theerathean.
Faculty of Science.
University of the Thai Chamber of Commerce.
Vibhavadee-Rangsit Rd. Dindang
Department of Information & Communication Technology.
Bangkok 10400
Thailand
Application Set
Transport Set

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The Open Systems Interconnection Reference Model
The architectural model adopted by the International Standards Organization (OSI) .
Bits
Frame
Packet
Segment
Data
Application Set
Transport Set

12. 12SC161: Principlesof Information Technology
The Open Systems Interconnection Reference Model
Application Interface.
Web browser, File Transfer, e-Mail
Application Layer
Presentation Layer Encryption Data.
ASCII, EBCDIC, UNICODE
Session Layer Transmission Control.
Simplex, Half-duplex, Full-duplexApplication Set
Transport Set
Transport Layer Flow Control.
Connection-Oriented, Connectionless
Network Layer Routes data.
IP Address
Data Link Layer Node to Node Transmission.
MAC Address
Physical Layer Send and Receive Bits.
Signal and Media.

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The Internet Model
The Internet model is a most widely used that it is accepted as a network architecture. The
Internet’s Protocol suite is called Transmission Control Protocol/Internet Protocol (TCP/IP).
OSI Model Internet Model Protocols
HTTP FTP POP3 DNS
TCP UDP
IPv4 IPv6 ICMP
Not Specified
User Data
Datagram
Packet
Segment
Encapsulation

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The Internet Model in Action.
Router
Router
Link Layer
Internet Layer
Transport Layer
Application Layer
Application Layer
Transport Layer
Internet Layer
Internet Layer
Internet Layer
Link Layer
Link Layer Link Layer
Link Layer
Link Layer

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A Local Area Network (LAN) is a communication network that interconnects a variety of
data communicating devices within a small geographic area and broadcasts data at high data
transfer rates with very low error rates.

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Client/Server
Microcomputer users, or clients, share
services of a centralized computer called a
server.
Peer-to-Peer
Computers share equally with one
another without having to rely on a central
server.

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A Topology is the physical layout of nodes in a network, which often dictates the type of
communications protocol used by the network.
Topologies of LANs.
Three Network Topologies.

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T-Connector
BUS
Desktop Computer
Terminator
• All nodes are connected to a single wire or cable, called a Backbone.
• Node is connected to a backbone with T-connector.
• Terminators are required at both ends of the backbone cable.
• A message (signal) that is sent by a node travels along the bus through all other nodes.

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Server
Desktop Computer
RING
• All the nodes are connected in a closed circle of cable.
• Electronic messages are passed around the ring.
• The Token determines which user on the network can send information. It is called
“Token passing”

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• All devices connected with a central Hub.
• The Hub monitors the flow of traffic.
• The Hub also acts as a repeater for the data flow and then retransmits the signals to
all other nodes.
Server
HUB
Desktop Computer

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23. 23SC161: Principlesof Information Technology
A Wide Area Network (WAN) is a data communications network that covers a
relativelybroad geographicarea and that often uses transmissionfacilitiesprovided by common
carriers such as telephone companies.
A WAN is contrasted to smaller Local Area Networks (LANs) and Metropolitan Area
Networks (MANs).
Home Network
Company Network
Internet Service Provider
(ISP)
InternetSatellite

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Transmission Facility.
What is the most efficient way to send message over a WAN network ?

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Transmission Facility.
Circuit switching : Best for voice.
Message

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Transmission Facility.
Packet switching : Best for data.
1
2
3

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Modulation.
The telephone system transmit analog signals, the transfer of a computer’s digital data over a
telephone line requires conversion of the data to an analog signal.
• The technique of converting digital data to an analog signal is called “modulation”.
• The technique of converting analog signal back to digital data is called “demodulation”
Analog signal
Digital signal
Modem
Modulates Signal
Modem
Demodulates Signal

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Multiplexing.
The multiplexing is a technique of transmitting multiple signals over a single medium. It is
performed at the physical layer of the OSI model. For multiple signals to share one medium. The
medium must be divided.
Frequency Division Multiplexing Time Division Multiplexing

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