Transcript CIS110 Unit2Ax

Unit 2
Section A
The Internet
A LITTLE HISTORY
The Internet has been around since:
1991
1984
1977
1969
1961
1956
The Internet was largely unnoticed for years
Mostly for military and education use before 1995
Two innovations caused it to explode in the mid-90s
Tim Berners-Lee created the World Wide Web in 1991
Two students at the University of Illinois wrote the first
graphical web browser, Mosaic, in 1993
Internet & World Wide Web are not synonymous
The Web is a subset of the Internet
Chapter 1, Slide
Introduction
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WHAT IS THE INTERNET?
The Internet is a communications infrastructure
Using a common communications protocol
Linking networks and servers worldwide
The Internet communication protocol is TCP/IP
(Transmission Control Protocol/Internet Protocol)
The goal: send data from one point to another
It’s a highly decentralized network
Internet servers are found everywhere… worldwide
Data can take many paths to a destination,
automatically routing around failing components
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Introduction
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WHAT IS A PROTOCOL?
All forms of communication follow a set of rules
You understand these words because they follow
the rules of the English language
If this were in Chinese, it would be gibberish to you
Source and recipient must follow the same rules
Computers must agree upon a set of rules for
communication, just like people do
There are many different sets of rules for digital
communication
Protocol is just a set of rules for communication
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THE INTERNET BACKBONE
The Internet backbone is a network of very
high-speed and high-capacity data lines
The backbone is like the Interstate Highway System
Consider driving from Waynesville to Nashville
First task is to find the quickest way to I-40
The slowest part of the trip is getting to I-40
Can only get on I-40 at an interchange
Once on I-40, it’s a non-stop trip at high speed
Similarly, internet data must get to the backbone
Chapter 1, Slide
Introduction
to Computers
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Unit 2A – The
Starting
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HOW DOES DATA GET TO THE BACKBONE?
Individuals contract with an ISP (Internet
Service Provider) to gain access to the Internet
ISP connects you to the Internet by providing:
A means to connect you to a local point of presence
A fiber optic line connects local point of presence to
backbone at a network access point (NAP)
Connection to ISP is like the street leading out
of your neighborhood… it takes you to US-276
The fiber optic line is like US-276… it takes you
to an interchange with I-40
Chapter 1, Slide
Introduction
to Computers
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Unit 2A – The
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CONNECTING TO YOUR ISP
Currently four major connection methods
Dial-up – uses voice grade standard phone line
Cable – uses cable television coaxial connection
DSL – uses digital signal on a standard phone line
Mobile broadband – uses cell phone system
Dial-up top speed is about 56Kbps
Top speed for other connections about 5Mbps
Dial-up, cable, DSL need some type of modem
Converts signal for transmission on the medium
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Introduction
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Unit 2A – The
Starting
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DIAL-UP CONNECTIONS
Advantages:
Setup is easy and service is inexpensive
Uses the standard modem already in your computer
Uses “plain old telephone service” (POTS)
Disadvantages
Very slow, top speed is 56 Kbps
Less reliable than cable or DSL
Only one person at a time may use the Internet
Ties up phone line when someone’s on the Internet
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Introduction
to Computers
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Unit 2A – The
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CABLE CONNECTIONS
Advantages:
Up to 90 times faster than dial-up
Highly reliable, very few “dropped” conversations
Multiple people may use Internet at the same time
Does not tie up your phone line
Disadvantages
Purchase/lease cable modem, service more costly
Some don’t have access to cable television service
You share bandwidth with your neighbors
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DSL CONNECTIONS
Advantages:
Up to 90 times faster than dial-up
Highly reliable, very few “dropped” conversations
Multiple people may use Internet at the same time
Does not tie up your phone line
Disadvantages
Purchase/lease DSL modem, service more costly
Unavailable to many, too far from switching station
Slower as distance from switching station increases
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Introduction
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Unit 2A – The
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MOBILE BROADBAND CONNECTIONS
Advantages:
Up to 90 times faster than dial-up
Internet access most anywhere “on the go”
Multiple people may use Internet if their laptop has
been “paired” with the phone
Disadvantages
Must purchase a data plan from cell provider
Few data plans offer unlimited access
Very slow connection speeds in some rural areas
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OTHER TYPES OF CONNECTIONS
Satellite
Fast and reliable, but more costly
The best and often only option for high-speed
access in most remote areas
Severe rain or snow can cause signal interruption
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Unit 2A – The
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BROADBAND CONNECTIONS
Cable, DSL, mobile provide broadband access
All use a wide range of frequencies or bands
Broadband is an “always-on” connection
Cable and DSL can be wired or wireless
Router needed for wireless access or multiple users
Most routers function as both wired or wireless
If using wired access, network port is used to connect
Allows a single internet connection to be shared
Mobile broadband is usually a wireless signal
A wireless router is built into many mobile devices
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Introduction
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A ROUTER PROVIDES A FIREWALL
A router also provides a firewall for security
A router hides your computer behind a firewall
Without one, your computer is directly accessible to
hackers on the Internet
With one, hackers see your router on the Internet
but not the computers hiding behind the router
A wireless router should require a password
If not, neighbors or passersby can “hitchhike” on
your wireless signal & use your internet connection
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DATA IS SENT TO AN IP ADDRESS
Every device connected to the Internet has a
unique number called an IP address
An IP address consists of 4 sets of numbers, each
separated by a period, ranging from 0 to 255
Why 0 to 255? An IP address consists of 4 bytes!
A typical IP address might be 204.84.169.23
247.271.13.87 is not a valid IP address. Why?
An IP address is like the address of your home
It’s unique! It’s where your mail is delivered.
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Introduction
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A TRIP ON THE INTERNET
Request the MSN web site in your web browser
Browser sends a packet to the MSN server
The packet contains:
IP address of the web site being requested (destination)
IP address of browser submitting the request (source)
Routers are the “traffic cops” of the internet
Look at destination IP address at data line intersections
Steer data toward the destination IP address
Each router successively steers the packet closer to its
destination
Packet eventually arrives at destination server
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A TRIP ON THE INTERNET
MSN server returns a web page by
Sending packets of data to requesting computer
Several small packets are sent containing:
IP address of computer making request (destination)
IP address of MSN server (source)
Data that makes up that web page
Routers use IP address to steer packet along the
Internet communication links back to your browser
Your computer receives several packets of data
Packets reassembled and web page displayed
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WHO USES IP ADDRESSES?
Instead of an IP address, you key in msn.com
when requesting the MSN web site
Msn.com is a domain name
Domain names automatically map to an IP address
Domain names much easier to use and remember
Try it yourself
Click on the web address http://151.193.224.81
Click on the web address www.travelocity.com
Both take you to the same web page
But www.travelocity.com is far easier to remember!
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Introduction
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Unit 2A – The
Starting
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LOCAL AREA NETWORKS & THE INTERNET
Large organizations do not provide an Internet
connection for each and every computer
Businesses and educational institutions like HCC
use a local area network to tie computers together
Computers on the network all share a single, highspeed, large bandwidth Internet connection
LAN’s are a more sophisticated version of the
personal area networks (PANs) found in homes
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Introduction
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Unit 2A – The
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OTHER PROTOCOLS ON THE INTERNET
TCP/IP is the overarching Internet protocol that
determines how data is transmitted
Other protocols dictate subsets of the Internet
World Wide Web - Hypertext Transfer Protocol (HTTP)
Receive Email - Post Office Protocol (POP3)
Send Email - Simple Mail Transfer Protocol (SMTP)
Send or Receive Files - File Transfer Protocol (FTP)
Voice Conversations - Voice Over IP (VoIP)
Control a remote computer - Telnet
Chapter 1, Slide
Introduction
to Computers
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Unit 2A – The
Starting
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