Lecture #7 -- Chapter 8
Download
Report
Transcript Lecture #7 -- Chapter 8
Welcome to CMPE003
Personal Computer
Concepts: Hardware and
Software
Winter 2003
UC Santa Cruz
Instructor: Guy Cox
Assignments
nd
2
Homework
Due Now!!
No late assignments will be accepted
January 19, 2003
2
The Internet:
A Resource for All of Us
Chapter 8
Part A
Objectives
Describe some of the history of the Internet
Explain what is needed to get on the Internet
Describe generally what an Internet service
provider does
Describe the rudimentary functions of a browser
Describe how to search the Internet
List and describe the non-Web parts of the
Internet
Explain some of the ongoing problems
associated with the Internet
January 19, 2003
4
History of the Internet
Government and Universities over 30 years
Who’s connected today?
Individuals
Educational institutions
Government/Military/Police
Research
Medical
Businesses
Everyone!
January 19, 2003
5
The Early Years
1969 – US Department of Defense and Rand
Corporation
Origins
Cold War – fear that a bomb could demolish computing
capabilities
Several computers, geographically dispersed, networked
together
Plan – if one computer was disabled, others could carry on
using alternative communication routes
January 19, 2003
6
The Early Years
Many WANs and LANs were installed, but
machines on the WANs could not access
information on the LANs..
Remote access was separated from local access
A single cohesive network was desirable.
January 19, 2003
7
The Early Years
US Department of Defense had a similar
scenario – lots of autonomous networks that
could not interoperate
The DoD funded network research in the
early ’70s through (D)ARPA creating various
network technologies, including a research
WAN called ARPANET.
January 19, 2003
8
The Early Years
ARPANET allowed researchers the
opportunity to build a working test-bed for
networking ideas.
Solved incompatibility issues
Solved interoperability issues
Created an internetwork of LANs and the WANs
The Internet is born
January 19, 2003
9
The Early Years
G2
G1
UCB
LAN
UCLA
LAN
January 19, 2003
ARPANET
Backbone
G4
G3
MIT
LAN
DARPA
LAN
10
The Early Years…
Internet Software
Internet Protocol (IP)
Transmission Control Protocol (TCP)
Provides basic communication
Handles the addressing and routing
Provides services for applications to communicate
Packetizes message, reassembles message at the
destination
The “TCP/IP Internet Protocol Suite”
January 19, 2003
aka TCP/IP
11
The Early Years
ARAPA placed the research and software into
the public domain.
All information was freely available to any person
or vendor, allowing them to create devices or
networks that would interoperate with the Internet
technology.
Improvements were documented and made
publicly available.
This philosophy is called an Open System
January 19, 2003
12
The Early Years
Internet documentation
On-line and accessible from the Internet
Reports for improvements to the Internet were initially a
two step process
Request for comments (RFC) went out first
Internet Engineering Note came out with the comments
as the final report.
Today the RFC remains as the definitive documentation for
the Internet
On-line at www.faqs.org/rfcs/
January 19, 2003
Also www.ietf.org/rfc.html
13
The Early Years
The UNIX operating system
Built at Bell Labs in the early ’70s
UNIX given to universities to study
UC Berkeley team added LAN software
January 19, 2003
Distributed to others via the Berkeley Software
Distribution (BSD) and became known as BSD UNIX
(The ancestor of today’s Free BSD)
14
The Early Years
ARPA negotiated with UCB to add the TCP/IP
suite to the BSD UNIX release.
Gave large number of universities access to
study networking, and deploy it in their
departments.
1982 the US Military chose the Internet as its
primary communication system.
1983 the ARPANET began running TCP/IP
exclusively.
January 19, 2003
15
The Early Years
Incredible growth from day one..
In 1982 ~200 machines were connected
By 1983 the number had doubled
With growth comes the problems..
January 19, 2003
Static lists of machines need updated
Limited memory space …
Software updates..
16
The Early Years
The Computer Science Network (CSNET)
Sponsored by NSF in early `80s
Goal was to connect every Computer Scientist in the
country over one network.
CSNET was deployed using TCP/IP and the Internet
By mid 1980s most major university and research labs
were connected to the Internet
Graduate students began to investigate the details of
these new technologies, and include them in their
research topics.
January 19, 2003
Developed new applications
Extended the technology
17
The Early Years
The IAB (Internet Activities Board)
(Now known as the Internet Architecture
Board)
Original controlling body to coordinate TCP/IP
research and Internet development.
Chairman – Internet Architect
RFC Editor
Formed volunteer task forces to solve problems
January 19, 2003
Task forces generated new RFCs
18
The Early Years
The IETF (Internet Engineering Task Force)
Originally chartered for short-term Internet
development.
Now is responsible for most of the Internet
technical development
Working groups meet and create the RFCs
January 19, 2003
Manet, ipsec, tcp…
19
The Early Years
NSFNET
NSF recognized the importance of the Internet to
the scientific community.
Interconnected the supercomputer centers
around the US with a TCP/IP WAN
January 19, 2003
Proved useful, but small
NSF looked for ways to improve the ARPA Internet
20
The Early Years
The NSFNET Backbone
1988 WAN established as main backbone of the
Internet
January 19, 2003
MCI – long distance transmission lines
IBM – dedicated computers and software
MERIT – network operation
21
The Early Years
The ANS Backbone (Advanced Networks and
Services)
Consortium of MCI, IBM & MERIT
Allowed the government to begin privatization of the
Internet
1992 – WAN was built to serve as the Internet
backbone
January 19, 2003
ANSNET, 30 times NSFNET capacity
22
The Early Years
Exponential growth …….
80000000
70000000
60000000
50000000
40000000
30000000
20000000
Computers
Connected
10000000
0
1983 1987 1991 1995 1999
January 19, 2003
23
The Early Years
By 1999, the Internet was growing so fast that,
on average, a computer was added to the
Internet every second – and the rate continues
to increase.
An interesting fact:
At any time from 1983 through 1999, approximately
half the growth of the Internet occurred in the previous
12 months…
So, after you have been “on” the Internet for
only one year, you will have had more
experience than half the other users….
January 19, 2003
24
The Early Years
Growth – Good and Bad
Good for vendors
Bad for the IETF
Predictions of imminent collapse
January 19, 2003
March 1993, Summer ’97
Technology improvements have kept up with
bandwidth and switching speeds required.
25
The Early Years
The Hard limit – Address space
The IP protocol is limited to a number contained in
4 bytes (32 bits)…
Byte 3
Byte 2
Byte 1
Byte 0
•This limits the number of possibilities to 232 = 4,294,967,296
•There are solutions – IPv6, NAT
January 19, 2003
26
The Early Years
Summary
The Internet began as an ARPA research project.
The TCP/IP protocol software was developed to
make the Internet operational.
The Internet is an Open System, with the
technology freely available to all.
The Internet documentation is available on-line in
the form of reports known as RFCs.
January 19, 2003
27
The Early Years
Summary (continued)
BSD UNIX distributed TCP/IP suite freely to
universities in the early 80s
1982 US Military adopted TCP/IP as primary
communication standard
Exponential growth from its inception
IAB formed to coordinate development
IETF - major technical development body
January 19, 2003
Working groups
28
The Early Years
Summary (Continued)
1988 – NSFNET Backbone
1992 – Privatization (ANSNET)
Exponential growth from its inception
Half of the users today have been there less than one
year……
IP Address 32 bit limitation
January 19, 2003
29
Tim Berners-Lee
1990
Perceived a spider’s web of computers with links
from computer to computer
CERN site
Dr. Berners-Lee’s physics laboratory
Birthplace of the World Wide Web
Easy movement due to links
Hypertext
Hyper-region
January 19, 2003
30
Marc Andreessen
1993
Created browser software
Mosaic – first graphical browser
Became Netscape (now owned by AOL)
Provided attractive images and a graphical interface
permitting users to click on pictures as well as text
January 19, 2003
31
Internet Explosion
September 2002
Over 600 million users worldwide
Part of our daily lives
Four factors
TCP/IP standard
Ability to link from site to site
Ease of use of browser
Growth of PC and LANs that can connect
January 19, 2003
32
Global Internet Usage
January 19, 2003
33
URL
Uniform Resource Locator
http://domain-name.top-level-domain/last-section
Unique address of a web page or file on the
Internet
Case-sensitive
January 19, 2003
34
http
hypertext transfer protocol
http://domain-name.top-level-domain/last-section
Protocol – rules
Communication using links
January 19, 2003
35
Domain name
http://domain-name.top-level-domain/last-section
Address of the ISP
Domain names are registered
Ongoing fee is paid for each domain
name
January 19, 2003
36
Top-level Domain
Represent the purpose of the organization of entity
.com
.gov
.edu
.org
.net
May be a two-letter country code
January 19, 2003
37
Last section
http://domain-name.top-level-domain/last-section
Directories and file names that specify a
particular web page
January 19, 2003
38
Getting Started
Computer with a modem or NIC
Internet service provider (ISP)
Browser client
Other related software
January 19, 2003
39
Internet Service Provider
Vehicle to access the Internet
Provides
Server computers
Email,
January 19, 2003
News, etc..
Software to connect
40
Wireless Internet Access
Supports mobile handheld devices
Text pagers
PDAs
Pocket computers
Web-enabled cellular phones
Applications
E-mail
Checking weather
Making airline reservations
January 19, 2003
41
Wireless Internet Access
Need
Account with wireless access provider
Cellular modem card or adapter
Slow
download speeds
Wireless Application Protocol (WAP)
Convert web pages into format for mobile devices
Resized for limited display area
Fewer graphics transmitted
January 19, 2003
42
Browser
Netscape Communicator
Microsoft Internet Explorer
Mozilla
January 19, 2003
43
Browser
Used to explore the Internet
Dials the ISP
Display web pages
January 19, 2003
44
Browser
Welcome
Parts of the window
Banner
Menu
Bar
Buttons
Bookmarks
“Hot List”
Status
Line
January 19, 2003
URL
Textbox
Control
Panel
Browser
Logo
Scroll
Bar
Display
Window
45
Browser
Functions and Features
Browser
display window
Displays contents of web page from each Internet
site visited
Screen limits how much of the site you can view at
a time. The page can be scrolled using the scroll
bar to see its entire contents
line – progress of data being
transferred and other messages
Status
January 19, 2003
46
Browser
Functions and Features
Welcome
banner on title bar
Browser logo – animation indicates you are
in the process of moving to a new site
Hot list
Bookmark
Favorites
Store your favorite URLs
Browser
January 19, 2003
control panel – menus and buttons
47
Browser
Menus and Buttons
Pull-down
menu
Buttons
Convenient shortcuts for commonly used functions
Click button rather than locate command from pulldown menu
January 19, 2003
48
Browser Support: Frames
Divides page into
rectangular
sections
Each section
displays web pages
independently
Several small pages
on one screen
Can be scrolled
independently
Can be replaced
with other pages
independently
Not all browsers
support frames
January 19, 2003
49
Plug-ins
Software
that increases the functionality of
a browser
Audio-video
Image viewing
Download
from web sites
Install
Example
Adobe Acrobat Reader
Shockwave
January 19, 2003
50
Programming
Java
Write software that is machine independent
Programming language
Dancing icons
Sound clips
Flashing messages
Banners that scroll
Applets – Permits dynamic web pages
Display animations
Receive input
Perform calculations
January 19, 2003
51
Programming
ActiveX Controls
Capabilities similar to Java
Browser must be enabled to support applets /
ActiveX Controls
Security issues
January 19, 2003
52
Moving Between Sites
Clickable
categories in the browser
Sports
Weather
News
Technology
Comic strips
Enter
the URL in the address text box and
press <Enter>
January 19, 2003
53
URL
Uniform Resource Locator
http://domain-name.top-level-domain/last-section
Unique address of a web page or file on the
Internet
Case-sensitive
January 19, 2003
54
Processing Requests
URL
User
enters a URL
User computer sends request to the ISP
server
ISP server sends request across networks of
TCP/IP computers
Destination site is reached
Content is transmitted back to your computer
(process in reverse)
January 19, 2003
55
Searching the Internet
Search engine
User specifies a search request
Browser links to Search Engine
Request returns matching pages based upon the
Search Engine’s database
Results presented
January 19, 2003
56
Processing Requests: Search
Engine Database
Search Engine builds database
Searchable terms
Related web sites
Spider, robot, bot
Follows links across the web
Automatically indexes pages to a database
One
word
All words
Pages may be submitted by the owner
January 19, 2003
57
Processing Requests: Search Engine
Database
Request
same search using different
engines yields different results
Databases built independently
Size
Content
Search methodology
– atomically puts the same
request to several search engines
Metasearch
January 19, 2003
58
Processing Requests
Directory vs. Search Engine
Directory
Human involvement
Sites organized by content category
May concentrate on specific content areas
Subjective decisions regarding inclusion and
importance
Search Engine
Spider, robot, or bot automatically builds database
Index on a few keywords
Index on all words on web page
January 19, 2003
59
Processing Requests: Search
Engine Limitations
Index
only a fraction of the Web
Approximately 20% to 33% of sites
More web pages added daily
Solution
Same request to several search engines
Metasearch
January 19, 2003
60
Search Tools
Directories
Yahoo!
NetGuide
Metasearch Sites
MetaCrawler
Dogpile
January 19, 2003
Search Engines
AltaVista
Excite
Google
HotBot
Infoseek
Lycos
Northern Light
61
Refine the Search
Add
words
Enclose words in “quotes”
Use Boolean logic
Examples
“World Trade Center”
Jordan AND NOT Michael
January 19, 2003
62
Other Uses of the Internet
Newsgroups
FTP
Telnet
E-mail
Internet
January 19, 2003
Relay Chat (IRC)
63
Newsgroups / Usenet
Large bulletin board divided by category
Posting and reading of messages that focus on
specific topics
Over 20,000 newsgroups
Functions
Conversation
File download
Newsreader software required (included with
most browsers)
January 19, 2003
64
Newsgroup Operations
Lurking
Posting
material
Inappropriate material
Flame
Flame
January 19, 2003
war
Moderated newsgroup
65
FTP Client
File Transfer Protocol
Download
files to your local computer
Upload files to another computer
Requirements to download file
Permission to download from a site
File is available for copying
FTP – do not need to identify
yourself to the remote computer
Anonymous
(But we do know your IP address)
January 19, 2003
66
Public Archives
Free files provided by educational institution or
the government
January 19, 2003
67
Telnet/SSH
Use your PC as a terminal providing remote access
to another computer
Permits
Log on to a host
Use as if you are sitting at a local terminal
Need account on the host system
Telnet software required (provided with most
browsers)
SSH available free on-line – must be installed
January 19, 2003
68
e-mail client
Send/receive written messages
Most used feature of the Internet
Mail server – Collects and stores e-mail
Mailbox – Assigned to each user
E-mail address
User name
@
Domain of the mail server
[email protected]
January 19, 2003
69
e-mail
Client Software Functions
Retrieve
Create
Send
Store
January 19, 2003
Print
Delete
Address book
Attach files
Filters
70
IRC: Internet Relay Chat
January 19, 2003
71
Not Quite Perfect Yet
Unregulated
Useless
web sites
Misinformation and misstatements on web
sites
Concern over government censorship
Security & Privacy Issues
January 19, 2003
72
Not Quite Perfect Yet: Social
Issues
Behavior
problems
Who is out there?
What are they doing?
Netiquette
Suggestions for appropriate behavior
Example: TYPING IN CAPS is shouting
January 19, 2003
73
Midterm #1
Wednesday – January 29
Chapters 1 – 4 and 8
~50 questions
Multiple choice
Bring Scantron form
#F-1712-ERI-L
(big & pink)
Bring #2 pencil
Bring your student ID
January 19, 2003
Required to take exam
74