Transcript networks

9th grade review and
Computer Networks,
LAN , Topologies
Mrs. Imen Tekaya Bouaziz
Review: Internet services:
Mrs. Imen Tekaya Bouaziz
Internet services:
• Electronic mail or e-mail : allows users to exchange messages. Each
user of has a mailbox address.
• The World Wide Web or WWW: Allows computers to search (access) data
stored on a remote computer. The World Wide Web is a huge set of electronic
documents, images, and other 'information resources' linked by an abstract 'web' of
hypertext links and URLs.
• The FTP Used to transfer files (uploading and downloading) between computers.
• The electronic commerce or e-commerce Means selling (e-selling)
and/or buying (e-shopping) products and / or services on the Internet.
• Forums or Online discussion groups, where participants with common
interests can reply to a message, post and open messages.
Mrs. Imen Tekaya Bouaziz
Internet services:
CHAT
When two
(IRCor)more
When
computer
two or
users
more
can see
computer
and respond
users
to instant
can see
messages
and[in
respond
real time
(live)].
to
instant messages [in real time (live)].
AA social
social networking
networking
service
service
is an online
is anservice.
onlineSocial
service.
networking
Social
sites
networking
allow users to
share allow
ideas, activities,
and
interests
within their
individual
networks.
E.g.
sites
users toevents,
share
ideas,
activities,
events,
and
interests
Facebook,twitter,Myspace,…
within their individual networks. E.g. Facebook,twitter,Myspace,…
Video conferencing is a set of interactive telecommunication
technologies which allow two or more locations to interact via twoway video and audio transmissions simultaneously. e.g.
Skype,OoVoO,…
Mrs. Imen Tekaya Bouaziz
Internet services: e-mail
Task 2: Give the correct number for each step while sending an email from your yahoo mail account:
❺
❶
❻
❷
❼
❸
❹
In the box « Sign in to Yahoo! », type the email
address in the box « Yahoo! ID » and password in the
box « Password ».
Launch the browser
Click the button « New ».
Type the web site address “www.yahoo.com
Type the receiver email and the mail text; finally click
the « Send » button.
Click the link « Mail »
Click « Sign In » button.
Mrs. Imen Tekaya Bouaziz
Task3: Your want to send an email message to 4 of your friends: Fedi,
Amal, Ali and Eya. Complete the fields of the “compose message” window
to send the email, knowing that:
 Subject of message: Invitation
 The message: I invite you to my birthday tomorrow at 16:00, See you soon.
 Email addresses of your friends:
“Compose message” window:
[email protected]
m
(Principal
receiver)
[email protected]
Receivers
m
addresses:
(Secondary
receiver)
[email protected]
Can see these
[email protected]
[email protected] [email protected]
m
addresses in his
m
m
m
[email protected]
received
[email protected]
[email protected]
[email protected]
[email protected]
message:
[email protected]
m
[email protected]
(Secondary
receiver)
Mrs. Imen Tekaya Bouaziz
[email protected]
(Secondary
receiver)
Mrs. Imen Tekaya Bouaziz
REMINDING
❶ What is the Internet? Definition and examples of
protocols.
What do you need to connect to the Internet?
The e-mail and some other services.
What are Net Ethics that you should respect?
Mrs. Imen Tekaya Bouaziz
1) Internet: definition
• Internet : is an international, interconnected networks,
which allows to exchange (send and receive) information
according to Protocols which are a set of universal rules
for the exchange of information.
• It’s the biggest W.A.N, it’s made up of Networks and subnetworks. It can be connected (linked) by different types
of physical links (e.g. optical fiber, coaxial cable,
telephone line, satellite transmission, etc.)
Mrs. Imen Tekaya Bouaziz
Mrs. Imen Tekaya Bouaziz
Mrs. Imen Tekaya Bouaziz
d) What do you need to connect to the Internet?
• A powerful computer
• A modem (integrated or internal as an
expanding card or external looking like
box)
• A communication system (téléphone line,
ADSL, satellite transmission, etc.).
• A browser to surf the web
• a subscription with an Internet Service
Provider (ISP).
Mrs. Imen Tekaya Bouaziz
a) What communication protocols means?
Communication protocol is a system of digital message formats
and a set of rules that defines how computers communicate with
each other across networks, and how messages are exchanged in
or between computing systems and in telecommunications.
Protocols may include signaling, authentication and error
detection and correction capabilities.
Here some examples:
Mrs. Imen Tekaya Bouaziz
TCP/IP the set of communication protocols named from two of the most important protocols
used for the Internet and other similar networks: the Transmission Control Protocol (TCP) and the
Internet Protocol (IP).
HTTP Hypertext Transfer Protocol: is a protocol for networked data. <<HTTP is the
foundation of data communication for the World Wide Web…building a network by using logical
links (the so called hyperlinks) between the nodes (e.g. text or words). HTTP is the protocol to
exchange or transfer hypertext.>> wikipedia.
FTP File Transfer Protocol: Protocol for exchanging files. Used to transfer files (uploading and
downloading) between computers.
POP Post Office Protocol: Protocol used when we receive an email
SMTP Simple Mail Transfer protocol: Protocol used when we send an email.
Mrs. Imen Tekaya Bouaziz
b) Net Ethics or Netiquette:
• Is a set of rules, attitudes and behaviors that each Internet
user should adopt for mutual respect of persons and
intellectual property. You also have to verify the cyberreputation of the source of information and whether the
given information is correct or not.
• Cyber ethics: Respect the feelings,
property, and rights of others online.
•Cyber security: Make sure your computer
has up-to-date security software/hardware to
protect you and the people with whom you
communicate online from viruses and other online
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threats.
• E.g. of respecting intellectual property: you have to
respect copy rights, « so if people distribute programs
without the author's permission, it is illegal. » You have
to mention the source of information (e.g.
Webtography).
• E.g. of mutual respect of persons: you always have to
use a courteous language and adopt politeness rules
while sending e-mails or chatting with friends or
making a statement on “Face book “, also never
provide private information about you or other persons
without their consent to avoid physical or financial
jeopardy.
Mrs. Imen Tekaya Bouaziz
• Online addiction: Be aware that when
text messaging, playing online games, chatting,
or other online activities become more important
than friends, family, or schoolwork, it may
indicate an addiction that should be addressed
immediately.
• Online privacy: Protect your personal
privacy online to avoid physical or financial
jeopardy. Children should never provide
personal or financial information online without
the permission of a parent or other trusted adult.
Mrs. Imen Tekaya Bouaziz
Cyber  .Respect the feelings, property, and rights of
ethics others online.
Cyber  Never agree to meet in person strangers you
meet online.
safety
Cyber  Make sure that your computer has up-to-date
security software/hardware to protect you
security
and the people with whom you
communicate online from viruses.
Online  Be aware that when text messaging,
addiction chatting, or other online activities will be
more important than personal life.
Mrs. Imen Tekaya Bouaziz
Computer Network
Mrs. Imen Tekaya Bouaziz
Solutions
Comments
Copy the folder on CD then
each one will have his own
CD.
Waste of time and money.
When one of your friends
will need a file, he will copy
it on a removable support.
Waste of time because of
the number of copies.
Establish a connection
between computers in
order to share the
folder.
o Reliable solution.
o Consultation of the
folder’s contents at any
moment.
Mrs. Imen Tekaya Bouaziz
Presentation of Local
Network
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IT’S A COMPUTER NETWORK
Picture1
Picture2
Picture1: represents a group of computers linked together via cables
and they are exchanging data.
Picture2: a set of computers around the world linked together via cables,
satellites, waves, etc.
Mrs. Imen Tekaya Bouaziz
c) What is a computer network?
Task 3:
Complete the following definition with words from
information,
communicate, wires, share
this
list:
exchange,
computers,
connected,
computers terminals, and
 A computer network is a system of two or more ………………,
connected by …………,
wires cables, or a
communication devices* linked (……………..)
share
telecommunication system** in order to ……………..
resources and
exchange
…………………….information.
It allows computers to communicate
……………………. with each
other.
* Terminals, and communication devices: iPad; i phone; smart phones; e-book; PSP;…
**wires, cables, or a telecommunication system: are means of connection through wires or wireless connection.
Mrs. Imen Tekaya Bouaziz
Computer Network
A computer network is a set of computers (2 or more)
linked together and allowing the exchange of
information and the sharing of material resources
(printer, CD drive, Hard disk, …).
Share
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computers
A computer network is a system of two or more ……………..,
terminals, and communications devices linked (connected) by
wires (cables) or a telecommunications system in order to
………….
share hardware and software
……….
…………. resources. It allows computers
communicate with each other.
to ………………..
Mrs. Imen Tekaya Bouaziz
Picture 2
Figure 2
In a LAN we use special connectivity technologies
different from the WAN cabling.
Mrs. Imen Tekaya Bouaziz
Types of computer networks:
Networks may be classified according to a wide variety of characteristics such as:
Scale, the medium used to transport the data , Topology, Communication protocols used, Organizational
scope, etc .
• Types of computer networks according to the geographic scale: It depends on how much large is the area
where it spans.
Mrs. Imen Tekaya Bouaziz
Introduction to Computer
Networking
•
A computer network is literally, a network of computers. Each computer in it is connected
to another via a transmission medium such as an Ethernet cable.
There are many different kinds of computer networks, such a LAN, MAN or WAN. There
are also many different types of network topologies, expl a backbone network structures.
LAN (Local Area Network)
• LAN network is one of the commonly used network and one of the simplest. This network
connects computer over a small distance such as within a building or a single computer lab
consisting of many computers. This network do not contain more than one subnet
because they are controlled by one administrator. Advantage of using this network is small
distance data sharing cause less errors and noise are minimum. Data transfer rate is 10 to
100 mbps. Coaxial cable and CAT 5 cables are normally used for connection.
PAN (Personal Area Network)
• This network is setup in the environment of an individual user which refers to the
interconnection of devices or gadgets within range of 10 meters. Interconnected devices
must be a laptop computer, PDAs, cellphones, printers, PCs or othe computer devices.
Sometimes Pan is also known as wireless personal area network(WPAN). This is the
technology that could enable wearable computer devices to communicate with other
nearby computers and exchange information and data.
Mrs. Imen Tekaya Bouaziz
Types of computer
networks (scale)
MAN (Metropolitan Area Network)
• This network is same as LAN but cover a distance an entire city or
campus and formally connected with LAN. This network is larger than
LAN but smaller than WAN network that we discuss later.
Transmission media used by this network is fibre optic cables which
provide efficient and fast communication. This network can be up to
5 to 50 km but data transfer rate is low as compared to LAN. MAN
network is owned by organization and individuals like organization
with the different branches located in the city.
WAN (Wide Area Network)
• This network is slightly more complex in nature by connecting
computers together over a large distance. The network capable to
remotely connecting computers over a huge network and allowing
them to communicate even when they are far apart. This network
contain multiple LANs and MANs network such as internet using
routers to transfer data or information faster and securely. MAN
network is distinguished from other network in terms of geographical
range. Data transfer rate in this network depends upon ISP provider
and varies over the location. Sometimes it also use satellites and
microwave relays. Example of WAN is Internet.
Mrs. Imen Tekaya Bouaziz
Advantages of Networks
• File Sharing
The major advantage of a computer network is that is allows file sharing and remote file access. A person
sitting at one workstation that is connected to a network can easily see files present on another workstation,
provided he is authorized to do so. This saves him/her the hassle of carrying a storage device every time data
needs to be transported from one system to another. Further, a central database means that anyone on that
network can access a file and/or update it. If files are stored on a server and all of its clients share that
storage capacity, then it becomes easier to make a file available to multiple users.
Resource Sharing
Resource sharing is another important benefit of a computer network. For example, if there are twelve
employees in an organization, each having their own computer, they will require twelve modems and twelve
printers if they want to use the resources at the same time. A computer network, on the other hand,
provides a cheaper alternative by the provision of resource sharing. All the computers can be interconnected
using a network, and just one modem and printer can efficiently provide the services to all twelve users.
Inexpensive Set-Up
Shared resources mean reduction in hardware costs. Shared files mean reduction in memory requirement,
which indirectly means reduction in file storage expenses. A particular software can be installed only once
on the server and made available across all connected computers at once. This saves the expense of buying
and installing the same software as many times for as many users.
Mrs. Imen Tekaya Bouaziz
Advantages of Networks
• Flexible Handling
A user can log on to a computer anywhere on the network and access his files. This offers
flexibility to the user as to where he should be during the course of his routine. A network also
allows the network administrator to choose which user on the network has what specific
permissions to handle a file. For example, the network administrator can allot different
permissions to User A and User B for File XYZ. According to these permissions, User A can read
and modify File XYZ, but User B cannot modify the file. The permission set for User B is read-only.
This offers immense flexibility against unwarranted access to important data.
Increased Storage Capacity
Since there is more than one computer on a network which can easily share files, the issue of
storage capacity gets resolved to a great extent. A standalone computer might fall short of storage
memory, but when many computers are on a network, the memory of different computers can be
used in such a case. One can also design a storage server on the network in order to have a huge
storage capacity.
Mrs. Imen Tekaya Bouaziz
LAN Vs. WAN: Differences Between LAN and WAN
• The two most popular network types today are LAN (Local Area
Network) and WAN (Wide Area Network). These two networks are
generally classified on the basis of their coverage area. Given below
are few points that differentiate these two networks.
• Typically, a local area network exists in a house or a university campus, while
a wide area network exists over many office buildings separated by a vast
distance. The office buildings in a WAN may be in different countries or even
continents. For example, the headquarters may be in USA, the regional
office may be in the UK, and the branch office may be in India. The workers
in these three buildings use a Wide Area Network to collaborate with each
other. The Internet can also be considered as a WAN, with the Ethernet
being a classic example of WAN. Let us have a look at the two structures and
their differences.
Mrs. Imen Tekaya Bouaziz
LAN Vs. WAN: Differences Between LAN and WAN
Mrs. Imen Tekaya Bouaziz
The DTR: Data Transfer Rate
The Data Transfer Rate (DTR) is the speed at which data can be
transmitted between devices. It’s often expressed in KB per second
(KB/s) or MB/s. it depends on the distance, the quality of the line, and
the wire gauge.
Mrs. Imen Tekaya Bouaziz
 The water transfer rate of these 2 apartments is not the same because the distance
between it and the water resource isn’t the same as well as the number of relays between
apartments is different.
 The water transfer rate of the apartment 3 is higher than the one of the
apartment 6 because the house 3 is near to the water resource.
 So, the power of the transfer rate depends on the distance (that
influence the time) and the number of relays ( the number of
computers).
Mrs. Imen Tekaya Bouaziz
Computer network
topologies
Activity 5
Mrs. Imen Tekaya Bouaziz
Computer Network Topology
When you look at these figures what is the difference
between them?
Mrs. Imen Tekaya Bouaziz
The difference between these networks is in their:
Shape, Structure, layout pattern
is the physical communication schema used by connected devices.
What is a computer network topology
• Network Topology refers to the shape or the layout, structure,
architecture of a computer network. It determines how different links and
nodes (Computer, printer, modem…) are connected to each other in a network
and It’s the schematic description of how they communicate.
• A physical topology describes how network devices are physically connected how devices are actually plugged into each other. We're talking about cables,
wireless connectivity, etc.
• A logical topology describes how network devices appear to be connected to
each other.
Mrs. Imen Tekaya Bouaziz
Computer network
topologies
Activity 7:
Mrs. Imen Tekaya Bouaziz
Network topologies
Bus Network Topology :
All devices are connected to a central cable called the
bus which is the backbone. Bus networks are relatively
inexpensive and easy to install for small networks but
hard for troubleshooting (in case there’s a problem)
Mrs. Imen Tekaya Bouaziz
Network topologies
Ring Network Topology :
All devices are connected to one another in the shape of a
closed loop. Ring topologies are relatively expensive and
difficult to install, but they offer high data transfer rate and can
span large distances.
Mrs. Imen Tekaya Bouaziz
Network topologies
Star Network Topology :
All devices are connected to central equipment: hub. Star networks are
relatively easy to install and manage. All data must pass through the hub.
Mrs. Imen Tekaya Bouaziz
Network topologies
Tree Network Topology :
integrates the star and bus topologies in a hybrid approach to improve
network scalability
Mrs. Imen Tekaya Bouaziz
Advantages
Bus topology
• Simple and easy
to set up
• Good for small
networks not
requiring higher
speeds.
• Cheaper than
other
topologies.
Ring topology
• Offer higher
data transfer
rate
• Can span large
distances (in a
LAN).
• It is less costly
than a star
topology.
Mrs. Imen Tekaya Bouaziz
Star topology
• A fault on one of
the nodes will
not affect the
rest of the
network
• More
performance
than other
topologies
• Easy to install
and manage.
Disadvantages
Bus
topology
Limited cable length and
limited number of nodes.
If there is a problem with
the cable or one node
fails, the entire network
goes down.
Low security
Ring topology
More expensive than the Bus Top
and difficult to install.
Star
topology
The failure of the hub
makes the network
inoperable.
Any moves, adds and changes of
devices can affect the network.
Data packets must pass through every
computer between the sender and
recipient therefore this makes it slower.
If any of the nodes fail then the ring is
broken and data cannot be transmitted
successfully.
Cabling more expensive
and Extra hardware
required (hub , switch)
45
Computer Network
Activity9
Mrs. Imen Tekaya Bouaziz