Transcript Connecting to the Internet

CIT 1100
In this chapter you will learn how to:
 Describe the hardware used to connect
to the Internet
 Explain protocols and software used
with networking and the Internet
 Discuss Web content and Web-delivered
services
Millions of smaller networks connected together form
the Internet. Like telephone network, the Internet is a
"supernetwork" of smaller networks
 It was designed to make certain that nothing could
stop the flow of communication, not even a nuclear
attack, so they specified a highly decentralized
network with multiple connections between the
various computers
 The heart of the Internet- the backbone - consists
of many university, corporate, and government
networks, connected together via thick bundles of
glass filaments, called fiber optic
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Specialized devices were developed that would
automatically route traffic to the proper destination
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Routers provide multiple paths to
multiple end points
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In the event a cable gets cut, or a router fails the
network can continue to route messages, routers
can easily find alternate paths
Routers provide connection points between networks
and determine the route for a data packet to take from
the source network to destination network
 Routers range from high-end machines that direct
huge amounts of Internet traffic to the little box
attached to your cable modem at home
 Home routers often offer multiple functions, most
have built-in switches and wireless access points
 Routers know the destination of data because routers
use TCP/IP the common protocol of the Internet
 They read network ID of each data packet and send it
by the shortest route they know to its destination
Getting your computer connected to the Internet
requires some sort of intermediary network with
a router into which you can tap. This router
connects to the Internet through an Internet
service provider (ISP)
Establishing a link between your computer and the ISP requires
three things:
 Some kind of network device on your computer, like a modem
or network card
 A cable or radio transmitter that enables the network device
to access the world outside your door
 Programs to make that hardware go, like the built-in network
software in Windows and TCP/IP installed

The least expensive Internet connection is
called dial-up networking. It consists of three
pieces:
◦ A modem
◦ A working telephone line
◦ An ISP
Early on, people realized that computer
information traveled slowly over regular analog
telephone lines. The concept of an Integrated
Service Digital Network (ISDN) began in1984
 It was supposed to evolve into a completely
digital telephone system so that data would go
faster through phone lines.
 ISDN never caught on as was expected because
other, faster technologies soon came along
such as DSL and cable
 ISDN supports data transfer rates of 128 Kbps.
Broadband connection gives you access to the
Internet through a single high-speed connection
 Always on, as opposed to a dial-up connection
 Two technologies dominate the broadband
connection field
◦ Cable
◦ DSL
Cable connections use regular cable TV cables to
delivering TV programming and high speed
internet access
 Supports upload speeds of up to 1.5 Mbps and
download speeds from 2 to as high as 24 Mbps
 Cable connections use a cable modem that
connects to a NIC in your PC via an Ethernet cable
 Cable TV companies take advantage of the fact
that their cable TV signal occupy only a fraction
of the capacity of the cables running into your
home leaving room for internet access
DSL makes use of the fact that standard copper
telephone lines can handle a much greater range
of frequencies, or bandwidth, than what is
needed to transmit voice during phone calls
 DSL uses this extra bandwidth capacity to send
data over telephone wires without disturbing
their ability to carry voice conversations
Once you have a physical connection to the
Internet, your computer, switch, and router all
start talking to one another exchanging data.
 In order to know how to communicate, they
need to use a predetermined language
Protocols fill that need
A major issues for early computer networks have
never been which pathway you use to send
information. Rather, they're concerned with how you
send the information so that it goes to the right place
and it is understood
 This became a big problem for the U.S. military, the
Navy bought their computer equipment from one
company, the Army from somebody else, each being
proprietary
 They couldn't send information back and forth, since
these different systems had different ways of
treating information
 The Department of Defense created a common
protocol that would run on any platform TCP/IP
Protocols are the ”Rules of the Road” when
establishing communications
 Transmission Control Protocol/Internet
Protocol (TCP/IP) protocol suite does the same
thing for networks,
 Providing a common set of rules and guidelines
for electrical signals, packaging of information,
error correction, security, etc.
Transmission Control Protocol (TCP) controls the
sending and receiving of information
 Two computers communicating use TCP to make
a connection and handle flow of data between
them
 Computers use the Internet Protocol (IP) to
determine packaging and labeling of data
 When data is sent its neatly cut up and packaged
into bits of information that are all the same size
The Operating System uses IP to determine how to
package the data, the operating system on the
receiving computer knows how to unpack the
information (and how to put it back together)
 To address the data so it is sent to the correct
endpoint your operating system uses IP to put a
numerical destination and source address-called
IP addresses-onto the packets
 IP addresses follow specific conventions. Most
commonly, IP addresses have four sets of
numbers ranging from 0 to 255, separated by
periods, like this: 192.168.1.52.
There are two different components to an IP
address:
 The Network ID defines the network
 The Host ID describes your node-the computer
you use to access the Internet
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Special computers, called Domain Name Service
(DNS) servers keep databases of IP addresses and
their corresponding names
 For example it may be hard to remember
74.125.65.106 but most people can remember
Google.com
 When you enter WWW.Google.Com into your
browser the DNS server responds with the actual IP
address, otherwise your browser would not be able
to locate Google
 For a small annual fee the ISP will maintain DNS
settings allowing users to quickly locate web pages
Open a Browser on a PC
“Hey who is WWW.Google.com?”
The ISP has a DNS server that will resolve
URL to an IP Address
Internet
That’s 74.125.95.106
The first thing that must happen is the
Name www.google.com must be resolved to
an IP Address
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
DHCP Dynamic Host Configuration Protocol
enables you to create a pool of IP addresses
that are given temporarily to machines
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IP Address: 192.168.1.17
the pool of IP
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Default Gateway:192.168.1.1
I’ll let you know
The PC now has an IP Address
It knows the address of the DNS server
It knows the Default Gateway to send
any internet traffic to.
After you've established a connection between
the PC and the ISP, you can do nothing on the
Internet without applications designed to use
one or more TCP/IP services:
◦
◦
◦
◦

The World Wide Web
E-mail
FTP (File Transfer Protocol)
VoiP (Voice over IP)
Each of these services requires a special
application each having special settings
The Web provides a graphical interface for the Internet Web
servers, providing Web sites that you access by using HTTP on
port 80
 Using Web-browser software, you can click a link on a Web
page and be instantly connected the Web server anywhere
in the world
 One thing the protocol HTTP lacks is security. When you
want to buy something from an online retailer you don't
want someone else covertly capturing your credit card
number
 Secure Sockets Layer (SSL) security protocol, used to create a
secure connection to Web sites which has been incorporated
into a secure web browser HTTPS
 HTTPS is very similar to HTTP but uses a different port
number 443
The File Transfer Protocol (FTP), using ports 20 and 21,
is a protocol used to share files between systems
 Instead of typing in a Web address and seeing a Web
page, typing an FTP address like ftp://ftp.cise/ufl.edu
brings you to a file and folder directory structure
 Here, you can upload and download files (if you have
permission to do so)
E-mail clients, such as Microsoft Outlook need to
be configured before you can use them to access
your e-mail, fill in your e-mail address and
password
 Next you add the names of the Post Office
Protocol ver. 3 (POP3) or Internet Message
Access Protocol (IMAP) server and the Simple
Mail Transfer Protocol (SMTP) server
 POP3 or IMAP server is the computer that
handles in-coming (to you) e-mail, SMTP
handles outgoing mail
POP3 is the most widely-used standard,
although the latest version of IMAP, IMAP4,
supports some newer features POP3 doesn't
 IMAP4 enables you to search through
messages on the mail server to find specific
keywords, then select the messages you
want to download onto your machine
 Even with the advantages of IMAP4 over
POP3, the vast majority of incoming mail
servers use POP3
You can use Voice over IP (VoiP) to make voice calls over
your computer network
 Allowing you to use the extra capacity on the data
network for phone calls
 VoiP works with every type of high-speed Internet
connection such as DSL and cable
 Remember when installing VoiP is that low network
latency is more important than high network speed
 Latency is the amount of time a packet takes to get to
its destination measured in milliseconds