Date post: | 30-Dec-2015 |
Category: |
Documents |
Upload: | josiah-evans |
View: | 28 times |
Download: | 0 times |
The Internet andWorld Wide Web
1
Objectives• Define the concept of a network• Describe the components of a network• Define Internet• Discuss how the Internet works• Understand ways to access the Internet• Define Domain Name• Describe the components of the URL• Define World Wide Web (WWW)• Describe the components of the WWW
2
The InternetWhat is a network?• A collection of
computers and devices connected together via communications devices and media– Modems– Cables– Telephone lines– Satellites
3p. 2.2
Next
What Is a Computer Network?
• Two or more connected computers• Major components in simple network
• Client computer
• Server computer
• Network interfaces (NICs)
• Connection medium
• Network operating system
• Hub or switch connecting multiple computers in a network
• Routers• Device used to route packets of data through different
networks, ensuring that data sent gets to the correct address
Components of a Simple Computer Network
Networks in Large Companies
• Components can include:• Hundreds of local area networks (LANs) linked to
firmwide corporate network
• Various powerful servers• Web site
• Corporate intranet, extranet
• Backend systems
• Mobile wireless LANs (Wi-Fi networks)
• Videoconferencing system
• Telephone network
• Wireless cell phones
Corporate Network Infrastructure
Key Digital Networking Technologies
• Client/server computing
• Distributed computing model
• Clients linked through network controlled by network server computer
• Server sets rules of communication for network and provides every client with an address so others can find it on the network
• Has largely replaced centralized mainframe computing
• The Internet: Largest implementation of client/server computing
Key Digital Networking Technologies
• Packet switching
• Method of slicing digital messages into parcels (packets), sending packets along different communication paths as they become available, and then reassembling packets at destination
• Previous circuit-switched networks required assembly of complete point-to-point circuit
• Packet switching more efficient use of network’s communications capacity
Packet-Switched Networks and Packet Communications
Data are grouped into small packets, which are transmitted independently over various Communications channels and reassembled at their final destination.
Key Digital Networking Technologies
• TCP/IP and connectivity• Connectivity between computers enabled by protocols
• Protocols: Rules that govern transmission of information between two points
• Transmission Control Protocol/Internet Protocol (TCP/IP) • Common worldwide standard that is basis for Internet
• Department of Defense reference model for TCP/IP• Four layers
• Application layer
• Transport layer
• Internet layer
• Network interface layer
TCP/IP Reference Model
• Application Layer– Defines the protocol that applications use to exchange data – FTP,
SMTP, HTTP, HTTPS• Transport Layer
– Provides communication session management between host computers.
– Defines the level of service and status of the connection used when transporting data.
– TCP• Internet Layer
– Addressing, routing, and packaging data packets called IP diagrams – IP
• Network Interface– Specifies details of how data is physically sent through the network,
including how bits are electrically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper wire.
The Transmission Control Protocol/Internet Protocol (TCP/IP) Reference Model
Types of Networks
• Signals: analog vs. digital
• Modem: Translates digital signals into analog form
• Local-area networks (LANs)• Campus-area networks (CANs)
• Peer-to-peer
• Topologies: star, bus, ring
• Metropolitan and wide-area networks
• Wide-area networks (WANs)
• Metropolitan-area networks (MANs)
• Spans a city and sometimes major suburs
Network Topologies
• Twisted-pair wire (modems)
• simplest and slowest
• Coaxial cable
• Copper wires surrounded by thick insulation
• Fiber optics and optical networks
• Dense wavelength division multiplexing (DWDM)
• Wireless transmission media and devices• Microwave
• Satellites
• Cellular telephones
• Transmission speed (hertz, bandwidth)
Physical Transmission Media
The Internet What is the Internet?
• Also called the Net• A worldwide collection of
networks that links billions of businesses, government agencies, educational institutions, and individuals
17
The InternetWhat are some of the services found on the Internet?
18
message board
instant messaging
file transfer
Web
chat
History of the InternetHow did the Internet originate?
19
History of the InternetWhat is a host node?• Also called a host• Any computer that
directly connects to a network
• Often stores and transfers data and messages
• Provides network connections for other computers
• Four original nodes on ARPANET
20
University of California at Los Angeles
University of California at
Santa Barbara
University of Utah
Stanford Research Institute
History of the InternetWhat is NSFnet?• The National Science Foundation’s network• Five supercomputer centers• Connected to ARPANET in 1986
21
NSFnetARPANETThe Internet!
History of the InternetHow has this network grown?
22
Today
More than 1 Billion users
1984
More than 1,000 host nodes
1969Four host nodes
23
From Research Project to Information Infrastructure
Growth In The Number Of Internet Hosts
24
The Web and Commercialization of the Internet
25
Growth Of The World Wide Web
26
New Structure for the Internet
• The Internet is organized around four network access points (NAPs).
• A different company operates each of these NAPs.
• These companies sell access to the Internet through their NAPs to organizations and businesses.
27
New Structure for the InternetNetwork Access Points On The Internet Backbone
28
How the Internet WorksWhat is an Internet service provider (ISP)?
• A business that has a permanent Internet connection
• Provides temporary connections to individuals and companies for free or for a fee
29p. 2.5
Next
History of the InternetWho provides the structure for the Internet today?
30
Networks from corporations, commercial
firms, and other companies
Telephone companies
Cable companies
GovernmentSatellite companies
How the Internet WorksWhat are other service providers?
31
How the Internet WorksHow can you connect to the Internet?
32
High speed connection• Employees• Computers part of a local area network (LAN)• Connect to service provider through a high-speed connection
line leased from local telephone company
Dial-up access• Home or small business
• Computer, modem, regular telephone line
• Dial into an ISP or OSP
Newer high-speed technologies• Home and small business
• Digital subscriber line (DSL) – provides high-speed Internet connections over regular copper telephone line
• Cable modem- provides high-speed Internet connections through cable television network
How the Internet WorksWhat is an Internet protocol (IP) address?• Number that uniquely identifies each computer or device
connected to the Internet• Four groups of numbers, each separated by a period• Number in each group is between 0 and 255
33
IP address 199.95.72.10
first part identifies network
last part identifies specific
computer
Tim Berners-Lee
• Created the World Wide Web
34
Director of the World Wide Web Consortium (W3C) at MIT
How the Internet WorksWhat is a domain name?• Text version of an IP address• Components are separated by periods• Each domain name represents one or more IP addresses
35
IP address 199.95.72.10
Domain name www.scsite.com
How the Internet WorksWhat is a top-level domain (TLD) abbreviation?• Identifies the type of organization associated with the
domain• Sometimes called dot com when TLD is com
36
TLD Abbreviation Type of DomainCom Commercial organizations,
businesses, and companies
Edu Educational institutions
Gov Government agencies
Mil Military organizations
Net Network provider
Org Non-profit organizations
The World Wide WebWhat is a Uniform Resource Locator (URL)?
• Unique address for a Web page• Browser retrieves a Web page by using the URL• Also called a Web address• Type the URL into the address text box on the browser and press
the Enter key to display a Web page
37
http://www.nationalgeographic.com/travel/index.html
address text box
address text box
The World Wide WebWhat are the parts of a URL?
38
protocol domain name path
Click to view Web Linkthen click URLs
http://www.nationalgeographic.com/travel/index.html
History of the InternetWho controls the Internet?• The Internet is a public, cooperative, and independent
network• No single entity controls or owns the Internet• Several organizations advise and define standards
39
World Wide Web Consortium (W3C)
• Oversees research and sets standards and guidelines
Internet2 (I2)
• Internet-related research and development project
• Develops and tests advanced Internet technologies
How the Internet WorksWhat systems control domain names?
40
Internet Corporation for Assigned Names and Numbers (ICANN)
Group that assigns and controls TLDs
Domain name system (DNS)
System on the Internet that stores the domain names and their corresponding
IP addresses DNS server
Translates the domain name into its associated IP
address
The World Wide WebWhat is the World Wide Web (WWW)?• Also known as the Web• A worldwide collection of electronic documents• Each document on the Web is called a Web page• Can contain text, graphics, sound, and video• Can contain built-in connections to other documents• A Web site is a collection of related Web pages
41
The World Wide WebWhat is a Web browser?• Also called a browser
42
Software program that allows you to access and view Web pages
Two popular browsers for personal computers• Netscape• Internet
Explorerp. 2.9 Fig. 2-6
Next
The World Wide WebWhat is downloading?
43
The process of receiving information, such as a Web page, onto your computer
from a server on the Internet
Can take from a few seconds to several minutes
You can speed up the display of pages by turning off the graphics and displaying only
text in most Web browsers
The World Wide WebWhat is a hyperlink?
• Also called a link• Built-in connection to
another related Web page or part of a Web page
• Allows you to obtain information in a nonlinear way
The World Wide WebHow can you identify a link?• Link can be a word, phrase, or image• Text links usually are underlined or in a color different
from the rest of the document• A graphical link may change its appearance when you
point to it
45
The shape of the pointer on the screen changes to a small hand with a pointing index finger when you position it on a link or point to the link
Click the link to activate it
The World Wide WebHow do you navigate a variety of links?
46
pointer
Some links display a different color when you point to them. Click the link to display its associated Web site or Web page.
pointer
Some links are underlined. Click the link to display the associated Web site or Web page.
pointer
Some links are graphical images. Click the link to display its associated Web site or Web page.
The World Wide Web
What is surfing the Web?• Links can point to an item on the same Web page, a
different Web page at the same Web site, or a separate Web page at a different Web site in another city or country
• The activity of jumping from one Web page to another is surfing
47
The World Wide WebWhat is a search engine?• A software program you can use to find Web sites,
Web pages and Internet files
48
Search text
A word or phrase entered in the search
engine’s text box
Also called keywords
Spider
A program that reads pages on Web sites in
order to find Web pages that contain the
search text
Also called a crawler or bot
The World Wide WebWhat is a hit?
• Any Web page name that lists as the result of a search
• The fewer ‘hits’ the better• Point of searching the web is to narrow
your search
The World Wide WebWhat is a directory?
• An organized set of topics
• Used by a search engine to aid in locating Web sites
• Each major topic has related subtopics
50
The World Wide WebWhat are the six basic types of Web pages?
51
advocacy Web page
informational Web page
business/marketing Web page
news Web page
personal Web page
portalWeb page
The World Wide WebWhat is an advocacy Web page?• Contains content that describes a
cause, opinion, or idea• Purpose is to convince the reader of
the validity of the cause, opinion, or idea
52
The World Wide WebWhat is a business/marketing Web page?• Contains content that promotes or
sells products or services• Often allows you to purchase
products or services online
53
The World Wide WebWhat is an informational Web page?
• Contains factual information• Many U.S. government sites provide information
54
The World Wide WebWhat is a news Web page?
• Contains newsworthy material• Stories and articles relating to current
events, life, money, sports, and the weather
55
The World Wide WebWhat is a personal Web page?
• A Web page maintained by a private individual who normally is not associated with any organization
• Reasons: job hunting and sharing life experience with the world
56
The World Wide WebWhat is a portal Web page
• Often called a portal• Offers a variety of Internet services from
a single, convenient location
57
The World Wide WebWhat services are often found on a portal?
58
maps
stock quotes
reference tools
sports and weather
search engine
local , national, and
worldwide news
free personal
Web pages
instant messaging
calendars
shopping malls and auctions
newsgroups or message
boards
chat rooms
p. 2.17
The World Wide WebWhat is a Web community?
• A Web site that joins a specific group of people with similar interests or relationships
• Usually offer special services to facilitate communication among members
59
newsgroup or message
board e-mail online photo
albumschat room