An Introduction to Internet

1
An Introduction to Internet

• - Shailesh

2
Greetings Newbie

• Newbie is Internet slang for a new Internet
  user. Because the Internet is vast and complex
  you can remain a newbie in some sense for a long
  time. It's not that it is difficult to learn.
  It's just diverse.

3
The Internet
The Internet is a "network of networks" that
links computers around the world. These computers
range from PCs and Macs to supercomputers, but
they all use a set of rules called TCP/IP to
exchange information. Driven by the popularity of
services like electronic mail, file transfer,
news groups, and the World-Wide Web, the
Internet's growth rate has been astonishing

• 1983 500 hosts
• 1987 20,000 hosts
• 1992 1,000,000 hosts
• 1994 4,000,000 hosts
• 1996 12,900,000 hosts
• 1997 19,540,000 hosts

4
TCP/IP

• The most accurate name for the set of protocols
  we are describing is the "Internet protocol
  suite". TCP and IP are two of the protocols in
  this suite. Because TCP and IP are the best known
  of the protocols, it has become common to use the
  term TCP/IP or IP/TCP to refer to the whole
  family.
• The file transfer protocol (FTP)
• Remote login. The network terminal protocol
  (TELNET)
• computer mail.

5
What You Can Do With It

• Log in to most of the world's libraries.
• Send email to your global colleagues.
• Join automated, special interest mailing lists
  and newsgroups and learn the latest.
• Search worldwide databases and obtain documents.
• Get tons of useful software, free!
• Be part of live, discussion groups or on-line
  classes .

6
Remote Login

• Over the Internet you can log in to any
  computer on which you have an account or which
  allows public logins. This includes many database
  services and almost all library catalogs. The
  means of doing this is called Telnet. Telnet is
  the remote login facility of Internet, and once a
  connection is made, works transparently. It's a
  heady experience to log into your account, Telnet
  to Yale to check on a book, then to U of Michigan
  for a weather report, then to Stanford for a
  bibliographic search--all from the comfort and
  convenience of home.

7
Magic

• Telnet makes your computer seem to be connected
  to a remote computer. What you enter from your
  keyboard is redirected to the remote computer.
  What the remote computer outputs is redirected to
  your monitor. It doesn't matter how far away the
  other computer is.

8
How To Do It

• To Telnet to another computer you simply type
  telnet followed by the address of the computer to
  which you are connecting.
• For example telnet newton.dep.anl.gov
• You can also use the remote computer's IP
  address telnet 146.139.100.50
• This sometimes works when a domain name will not.

9
Caught In The Web

• The World Wide Web, or WWW, or W3, or simply
  "the web," is an ambitious attempt to organize
  all the information available on the Internet as
  a set of interrelated hypertext documents.
  Hypertext is text that contains embedded links to
  other text, which contains links to yet other
  text, and so on, forming an interrelated web of
  active cross references. Each link is actually a
  pointer to another document or Internet resource.
  When you select a link you jump to that location.
  In this way the world of Internet information is
  tied together.

10
Hyper Text

• HTML HyperText Markup Language the language used
  to create Web pages.
• HTTP HyperText Transfer Protocol the
  client/server protocol for moving hypertext files
  on the Internet. Hypertext Text containing links
  that, when chosen by a user, will "jump" to
  another block of text, either in the same
  document or in another.

11
A Very, Very Brief History Of The Web

• Even though the
  European Laboratory for Particle Physics, CERN,
  can be credited for laying the foundation of the
  Web, the National Center for Supercomputing
  Applications, NCSA, developed many of the tools
  that made the Web usable to mere mortals.

12
What Is A Search Engine?

• Search engines are Web sites that can look-up
  and retrieve Internet resources based on a term
  you input. Let's say you want to look for Web
  sites that contain information about sky diving.
  You type the words sky diving in the search
  engine's dialog box and it will return a list of
  sites that feature sky diving in their content.
  There are many search engines on the Web you can
  use for free. The most popular is Yahoo! Lycos
  and HotBot are very good too. For detailed
  searches it's best to use more than one.

13
URL

• Tim Berners-Lee at CERN developed the World Wide
  Web using HTTP and one other incredibly useful
  concept the Universal Resource Locator (URL).
  The URL is an addressing scheme that lets
  browsers know where to go, how to get there, and
  what to do after they reach the destination.

14
URL Breakup
15
Web Power

• The web is so powerful because the links within
  documents may point to any type of Internet
  resource a Telnet session, a Usenet newsgroup,
  an ftp site etc. To use the web you need a
  browser--one as simple as the line oriented
  browser, Lynx, which is default with the shell
  account in VSNL, or as rich and complex as
  Netscape which runs as a Windows program capable
  of displaying images, playing sounds, and leaping
  to links with mouse click ease.

16
What's A Browser?

• A browser is a computer software program that
  allows a user to view Web pages while connected
  to the Internet. There are two browser programs
  currently in vogue -- Netscape Navigator from
  Netscape Communications and Internet Explorer
  from Microsoft Corporation. Both are equal to the
  task but Navigator is the most common program
  with roughly 70 percent of Web users using it. IE
  is quickly gaining a larger share of the action,
  though.

17
In a simplified overview, six things normally
happen when you fire up your Web browser and
visit a site on the World Wide Web

• 1.Your browser decodes the first part of the URL
  and contacts the server.
• 2.Your browser supplies the remainder of the URL
  to the server.
• 3.The server translates the URL into a path and
  file name.
• 4.The server sends the document file to the
  browser.
• 5.The server breaks the connection.
• 6.Your browser displays the document.

18
Electronic Mail

• Electronic mail, or e-mail, is a fast, easy, and
  inexpensive way to communicate with other
  Internet users around the world. Each day
  millions of mail messages traverse the Internet.
  They are carried by a standard system called SMTP
  (Simple Mail Transport Protocol), part of TCP/IP.
  An important restriction imposed by SMTP is that
  it can only handle TEXT data. That is, character
  data, like the characters you can type on your
  keyboard. To mail binary type data it must first
  be encoded as text data.

19
Uuencoded Files

• Most standard mail work only with text files, so
  if you want to mail a binary file, you must first
  convert it to a text file. This is what the
  program uuencode does. Uuencoded files are often
  given the file extension ".uue" To decode the
  file on the other end use the unix program
  uudecode. Uudecode does not remove the original
  encoded file from your directory after decoding.

20
Mailing Lists

• There are thousands of ongoing discussion groups
  carried
• out over the Internet via email. They work by
  subscription that is, if you have a special
  interest, you send your subscription request to
  the person (or computer) that maintains the
  mailing list and you are added to the number who
  automatically receive the group's common email
  each day. You may then post your invaluable
  insights to the group and read the less valuable
  insights of others by simply using your email
  program. Some groups are moderated, meaning that
  someone controls what gets posted, but most are
  not. Joining a list is called "subscribing," but
  there is no charge.

21
Controlling Your Mailing Lists

• The best advice anyone can get who is new to
  automated mailing lists is if you have an urge
  to subscribe, lie down until it passes! The vast
  riches of the lists invariably tempt the new user
  to oversubscribe. If you belong to more than 6
  groups, you are receiving far more mail than you
  can handle, because even a moderately active list
  can generate dozens of messages each day.

22
The second best advice is

• keep the acknowledgment letter you receive from
  the list immediately after subscribing. It
  contains valuable information on how to get off
  the list, to hold your mail when you are on
  vacation, etc., etc.

23
FTP

• FTP is an acronym for File Transfer Protocol, a
  very important part of the TCP/IP suite of
  protocols. It allows you to transfer any sort of
  file from any of thousands of remote computer
  systems to your own. You can transfer executable
  computer programs, graphics, sound, video or any
  other sort of files from remote archives to your
  own Internet host computer.
• And it's all free.

24
Which Way Is Up?

• When you transfer a file from a remote computer
  to your own, you say "I downloaded a file." When
  you transfer from your own computer to another
  one, you say "I uploaded a file. Down to you
  Up away from you. These terms can be confusing.

25
I Wish To Remain Anonymous

• The restriction to using remote computers is
  that you must have authorization to use them (an
  account, a user ID and a password). FTP gets
  around this problem by allowing a service called
  "anonymous ftp." That is, when you connect to a
  remote computer that allows anonymous ftp you
  enter your user ID as "anonymous." When asked for
  a password enter your full email address, eg
  fudd_at_sra.com. Some systems verify your email
  address, some do not, but in any event it is
  proper netiquette to provide it to the remote
  host.

26
Ye Be Properly Warned Says I

• Many ftp archives do not check their offerings
  for viruses. Before running any ftped file scan
  it with a good, current virus checker. All
  systems at SRA have McAfee Anti virus installed.

27
UseNet

• Usenet (short for user's network) is a giant
  collection of discussion groups, each centered
  upon a special topic of interest--boxing, bee
  keeping, photography, whatever. There are more
  than 5000 such groups within Usenet, the majority
  of which are devoted to topics of non-local
  interest. No one is in charge of Usenet. The
  procedures for transporting data (NNTP network
  news transport protocol), posting articles, and
  forming new groups have been established through
  tradition (Usenet began in 1979 at U of North
  Carolina). There is no control over content and
  there is no censorship. Whoever you are, you are
  sure to find lots of disagreeable things on
  Usenet--so ignore them.

28
The News?

• Though the discussion groups are called -
  newsgroups they have little to do with news in
  the traditional sense. They are more likely to be
  very specialized discussions of research trends,
  recipes, fan clubs... You name it. You can find
  most areas of human interest discussed somewhere
  on Usenet. It is a great place to go when you
  have specific questions and need expert answers.
  You simply post your question to the group and
  soon you will see an answer posted. It all
  depends on the group, of course. If your question
  is inappropriate, you can also expect to see some
  very deflating comments posted.

29
HTML

• HyperText Markup Language the language used to
  create Web pages. Web documents are ordinary text
  files that can be created with any word
  processing program. They include tags that
  control their appearance. For example, the
  boldface above is achieved with these tags
• ltBgttagslt/Bgt
• Tags can also define a word or phrase as a link.
  Selecting a link lets the user go to another
  document (or to another section of the same
  document). HTML documents (often called "pages")
  can also include color graphics and clips of
  digitized audio or video. Users need a web
  browser program (for example, Netscape Navigator)
  to view web pages.

30
Frames

• Frames give you a way to organize and structure
  the content of your HTML documents by letting you
  create compound documents that the user can view
  within the main window of the browser. The main
  window is divided into rectangular frames. Then,
  for each frame, a HTML document is specified
  which contains the content (text and images) to
  fill the frame.

31
Forms

• Forms provide a way to prompt the user for
  information and to carry out actions based on
  that input. A form consists of one or more input
  controls that the user uses to enter text and to
  select choices. the form collects the data and
  sends it to a destination specified in the form
  element.

32
CGI

• The Common Gateway Interface (CGI) specification
  lets Web servers execute other programs and
  incorporate their output into the text, graphics,
  and audio sent to a Web browser. The server and
  the CGI program work together to enhance and
  customize the World Wide Web's capabilities.

33
ISAPI

• Process Software has proposed a standard called
  ISAPI (Internet Server Application Programming
  Interface), which promises some real advantages
  over today's CGI practices.
• In a nutshell, the proposal says that it doesn't
  make sense to spawn external CGI tasks the
  traditional way. The overhead is too high, the
  response time too slow, and coordinating the
  tasks burdens the Web server. Instead of using
  interpreted scripts or compiled executables,
  Process proposes using DLLs (dynamic link
  libraries).

34
Java

• Java, a new programming language developed by
  Sun Microsystems, allows you to create
  self-contained programs and components (applets),
  that aren't tied to any specific hardware
  platform or operating system.

35
Scripting Languages

• Scripting languages are an intermediate stage
  between HTML and programming languages such as
  Java, C, and Visual Basic. HTML is generally
  used for formatting and linking text. Programming
  languages are generally used for giving a series
  of complex instructions to computers. Scripting
  languages fall somewhere in between. The primary
  difference between scripting languages and
  programming languages is that the syntax and
  rules of scripting languages are less rigid and
  intricate than those of programming languages.

36
Component Model

• A component model is an architecture and set of
  APIs that allow developers to define software
  components that can be dynamically combined
  together to create an application. A component
  model consists of two major elements components
  and containers.

37
Components

• Microsoft ActiveX controls are software
  components that provide dynamic features on your
  pages. For example, a stock ticker control could
  be used to add a live stock ticker to a page, or
  an animation control could be used to add
  animation features.
• Java Applets are software components that can be
  placed on Web pages however, they cannot
  interact with the page or with other Java applets
  on the page.
• Java Beans are the Sun Microsystems equivalent of
  ActiveX. Java Beans enhance the Java platform by
  allowing richer, more dynamic interaction.

38
Client In-Process Component

• Runs inside a container
• Explorer, Navigator
• Client-side scripts can provide illusion of
  interaction
• Leading technologies include Active-X and Java
  Beans

39
Server In-Process Component

• Runs inside a container
• Leading technology is a transaction server such
  as CICS or Microsofts Transaction Server (under
  DCOM)

40
Client/Server Tradeoffs

• Thick client
• Business logic runs on the client
• Offloads processing from server
• Can take full advantage of client OS
• Thick server
• Business logic runs on the server
• Centralizes processing on the server
• Returns to mainframe model

41
Client Tradeoffs

• Simple clients can use VBScript or JavaScript
• Serious clients need components (applets or
  Active X components), which changes the
  deployment model

42
Server Tradeoffs

• Simple servers can use common gateway interface
  (CGI)
• Serious servers need components (e.g. Microsofts
  Active Server Pages)

43
Tools Available

• HTML 3.2
• CGI
• ISAPI/ASP
• NSAPI
• Java

• Open Technology
• Open Technology
• Microsoft (Interdev)
• Netscape (Livewire)
• Open Technology (JDK/VJ/Symantec Cafe)

44
Conclusion

• This course was intended only as an
  Introduction to the vast and forever growing
  field of Internet. But now that you are
  Web-Smart, you should be able to find out more
  about the web and Internet.

45
Where do you want to go tomorrow?

• Check out http//www.amazon.com and order books
  online
• search for some information at http//
  www.yahoo.com
• Register at http// www.alumini.net and get a web
  presence
• Go to http// www.rediff.com for Desi stuff
• Or check out the Beeb at http// www.bbc.co.uk
• Indian bureaucracy at http// www.doe.gov.in
• For some tips on programming jump to http//
  www.programmersheaven.com
• Get tips on photography from New York Institute
  of Photography http// www.nyip.com
• Surf to http// www.cry.inindia.com
• At Case Western University you'll find some
  interesting tutorials on HTML - http//
  www.cwru.edu/help