Transcript Document

Internet- 6
Internet Background
- Soviet Union’s Sputnik, the first man-made
satellite
The Internet
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Started in 1969 as a U.S. government program to link
computers together.
At first, only a few people, mostly scientists and
professors, had access to the internet.
They knew the addresses of the computers that they
wanted to connect to.
There were no search engines and websites. The
Internet only provided a way to connect to different
computers separated by a great distance.
By 1990, the Internet was becoming more userfriendly.
Now there are at least 100 million computers on the
Internet and there are popular protocols for sending
email, accessing websites and transferring data
ISPs – Internet Service Providers
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To connect to the internet, you need an ISP.
Typically you can connect through a phone line,
satellite, TV cable or a special direct line
The ISP will have equipment like email servers, modems
to connect users and a router to connect to the rest of
the internet.
NSPs
 ISPs
then connect to Network Service
Providers (NSPs).
 These are big telecommunications
companies that provide access to the
fast fiber optic cables that make up the
"backbone" of the Internet.
 They might also connect through
satellites, phone lines, TV cable lines,
along with fiber optic lines
How is data transferred
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Your computer connects to your ISP's LAN through a
phone line. When that happens your computer is
able to use their network resources
This means you can use their router to connect to
the NSP. The NSP will forward your data to the
correct place and you will receive a reply
Your data can be sent using one of many types of
protocols for transferring data.
One of the most popular is TCP/IP which breaks the
data into packets and formats it in a certain way.
TCP/IP is used whenever a connection must be
established between two places. For example, to
make sure email is correctly sent both computers
must connect and talk to each other successively
before the email can be transferred.
Other Protocols
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TCP/IP is the foundation of most other protocols. It is responsible
for breaking data and sending it over long distances.
There are other protocols (see below) that work to help
communication between different services.
For example, a web browser and a web server use HTTP in order
to discuss how to retrieve web pages. The information they use
to communicate is then broken up according to the TCP/IP
protocol and then sent
Domain Name Servers
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The Internet would not be popular without easy to remember
names.
Every computer on the Internet needs an IP address, but
numbers are hard to remember, so Domain Name Servers (DNS)
provide a way for you to turn a name into an IP address or an IP
address into a name.
With this service, you can type in a name, your computer than
asks a DNS server for the IP, gets an IP, then sends the data to
that IP address
Connecting to the Internet Modems
The most common way to get on the internet is
through a modem
 A modem will dial an ISP over a regular phone line.
The ISP will have a computer pick up the phone
call.
 The ISP will then send your data through its network
service provider
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Modem Speeds
 Modem
speed is measured in “baud”
rate, or the number of bits it can send per
second over the phone line.
 There is a maximum baud rate of 56 Kbps,
but the speed also relies on the quality of
the phone lines and the connection
 Most of the time, you will not be able to
go faster than 44Kbps for downloads
Direct Connections
(DSL,ISDN,T1,T3)
 Your
internet session will last only until
you disconnect with a modem.
 Newer technology lets your computer
always be connected to the internet.
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ISDN – direct connection using special phone
lines
DSL – digital subscriber line – carries your data
over existing phone lines, but much faster
T1/T3 – Very expensive, very fast. You have to
lease cable lines from the phone company
for this connection.
LAN Security
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If your network or computer is always connected to
the internet, your computer might be vulnerable to
hackers (someone who tries to take over control of
your computer)
One way to protect your network is with a "firewall"
A firewall is a device (or computer) that examines all
data coming into a network link and decides
whether to allow it to pass through or deny it.
Hackers need to send data to computers in order to
take over. If it cannot send data, it cannot take over
the computer
Setting up a simple LAN
Setting up a LAN is not difficult.
First you must connect each computer with
an Ethernet cable to a hub/switch. When
you make a successful connection (and
your cable is good) you will see a light
appear on the hub.
 You must do this for the other computers as
well
 After physically connecting, you must
change the network configuration on each
computer to the accurate information so
each computer can connect
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Changing network properties
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After you log onto
the Windows XP
computer, go to
Start -> Control
Panel -> Network
Connections
This will allow you
to view and
change network
configuration
information
Changing Network Settings
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With network
connections open,
you will see a
picture that
represents your
Ethernet Card.
It will give the name
of your Ethernet
Card and tell if it is
connected
properly or not.
When you doubleclick on this you
can change
important settings
Changing Network Settings
You can view your
network settings by
looking at the
support option. This
will tell you things like
IP address, gateway
and netmask.
 If you look at
“Details,” you can
see even more
information about
your settings.
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Changing Network
Settings
 When
you are
ready to
change the
settings, go to
Properties
and then look
at “Internet
Protocol
(TCP/IP)”
What numbers should I put in?
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Click on “Use the following IP address”
This allows you to enter the IP address
Because you will be making a private LAN, you
should use the following form: “192.168.0.x”
This is a set of numbers that is reserved just for LANs
Usually the server on a network has the first number
(192.168.0.1) and other computers come after. You
are free to use any numbers between 1-254. If you
use 0 or 255, there could be problems
For the first computer, use 192.168.0.1 and the
second, 192.168.0.2
What numbers should I put in?
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For the netmask, you should use 255.255.255.0.
You will almost always use this number for all networks.
It is not necessary to have a gateway
You only need a gateway if you will be connecting your LAN
to the Internet. The gateway is another word for your router,
and the gateway number is the IP address of your router.
This router IP address is used when data will not travel to
another computer on your LAN. Your computer will
determine that the data must be sent to another network
and it will then use the router
The same goes for DNS. You can leave both blank unless you
are using the Internet. If you are using the Internet you will get
these IP numbers from your Internet provider (ISP).
Checking Networks
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After we enter the numbers and press “OK” how do we
know if the network is working?
The first thing to check is that the IP was set correctly and
the computer accepts it.
We can use a program from the command line called
“ipconfig” to check the IP settings
Checking Networks
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We also want to check to see if the network is working.
How can we tell if computers are talking to each other?
There is a program called “ping” that we use to check a
network connection
It sends a little piece of data to another computer. If the
computer gets it, the computer will respond.
This will show you if the network is correctly set up
Summary
 Network
physical structure and
communications protocol
 How the internet works
 TCP/IP and domain names
 Connection devices
 LANs