Lecture7.Computer_Networks

What is a Computer Network?
Two or more independent computers connected
together through a communication media form a
computer network. The computers are
connected in a network to exchange information
and data. The computers connected in a network
can also use resources of other computers such
as software packages and peripherals like
modems, printers, backup drives, or CD-ROM
drives. Networks are built with a mix of
computer hardware and computer software.

3.

Typical computer network

4.

Basic hardware and terminology in
networks
Основной комплект оборудования и терминология в сетях
1. Node (узел)
2. Client
3. Server
4. Hub
5. IP Address
6. Network interface cards (сетевая интерфейсная карта)
7. Repeaters (ретранслятор)
8. Bridges (мост соединения)
9. Switches (комутатор)
10.Routers (маршрутизатор)

5.

Classifications of Computer Networks
Computer networks can be classified by
considering following different aspects
as the basis.
• The scale (Масштаб)
• The connection method (Метод связи)
• The functional relationship (Network
Architectures) (Функциональные отношения
(Сетевая Архитектура)
• The network topology (Сетевая топология)

6.

Classification of computer networks
by scale
Тhe networks can be classified into six
classes abbreviated as
WAN,PAN, LAN, MAN and GAN.

7.

A personal area network (PAN)

8.

Local Area Network (LAN)

9.

Wide Area Network (WAN)

10.

Metropolitan Area Network (MAN)

11.

LAN, MAN, and WAN

12.

Classifications of networks based on
the topology
the main network topologies are listed
below.
• Bus (шина)
• Star (звезда)
• Ring (кольцо)
• Mesh (петля)
• Tree/Hierarchical
(Дерево/Иерархический)

13.

Bus Topology

14.

Star Topology

15.

Ring Topology

16.

Mesh Topology

17.

Tree Topology

18.

The Internet

19.

The Intranet and Extranet
• A typical intranet may provide the services
such as E-mail, File transfer, Real time chat,
web pages, video and audio streaming
services. Each service requires at least one
server to provide the service. For example, the
intranet of the Open University of Sri Lanka
maintains two main servers; a web server for
the OUSL web site and a Moodle server for the
service of delivery of on-line courses.

20.

Advantages of an Intranet
(Преимущества интранета)
• Commercial or confidential data is kept secured
within the organization.
• E-mails remain private and may also be encrypted.
• High bandwidth. No connection limits unlike the
Internet 62
• Reliable. The organization will have dedicated IT
personnel to keep things running smoothly.
• Information specificity tailored to the organization
or staff‟s needs can be published.

21.

The Extranet
• An extranet can be configured (set up) either
using a direct leased line linking all intranets
or by using a secured separate link created
across the participants as a VPN (Virtual
Private Network). The latter method is more
cost effective than the firs method.

22.

Advantages of Extranets
• A cost effective method to share and trade
information and all other data effectively at any
time to the authorized people (internal and
external) such as the customers, partners, investors,
suppliers who are included within the built up
extranet.
• A platform for companies to conduct business-tobusiness deals. Can assist in strengthening
relationships between two or more organizations.
• Useful when the staff of the company works outside
the office, from their homes, or sales sites so that
they can still be in with the company network with
the access permission.

23.

Self Assessment Questions
1.
2.
3.
Why do we need to connect computers?
What is a computer network?
Briefly describe the following network components. a. Client b. Server c.
Hub d. Router
4. What are the differences between a Hub and a Switch?
5. What is the use of a MODEM?
6. Briefly describe the following categories of networks. a. PAN b. LAN c.
WAN d. MAN
7. Briefly explain the classifications of networks according to the topology.
8. What is meant by Internet and Intranet? Why it is important to use
intranet than internet?
9. What is the most suitable connection method for the following; a.
Computers within a laboratory. b. Connect two computer laboratories.
10. List the advantages of having an Extranet for a company.

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