The document provides an overview of basic internet concepts including what the internet and world wide web are, parts of URLs, domain names, packet switching, standards bodies, and several common internet protocols. It defines the internet as a network of networks that connects computers worldwide and the world wide web as a system of interlinked web pages accessed via the internet. Key points covered include parts of URLs like protocols, domains, ports, and file paths. It also describes standards organizations like IETF and W3C and protocols for email (SMTP), file transfer (FTP), remote access (Telnet), and more.

1. Basic concept of internet
Ms.Snehal Kulthe
Department of Management Science

2. What is the Internet?
 The Internet is a network of networks of
computers.

3. Parts of the Internet
 World Wide Web
 Telnet
 Email
 Ftp

4. What is the World Wide Web?
 The World Wide Web is a hyperlinked network of
documents and other resources found on the
computers of the Internet.

5. Locating resources
 In order for the WWW to be useful, we need a way of
referencing all the resourses available.

6. URL
 What does URL stand for?
 Uniform Resource Locator

7. URL
 What does a URL do?
 A URL allows every resource (e.g. HTML page, image,
sound clip etc.) on the WWW to have a unique
address.

8. Parts of a URL
http://www.someaddress.com:8080/files/intro.html

9. Parts of a URL
 The protocol gives the method of
communication to be used. http is most
common, but you may see ftp as well.

10. Parts of a URL
 The domain name is the name of the computer
that has the resource you want.
 This computer is often called the host.

11. Domain names
 Domain names are broken down into different levels.
 E.g. www.someaddress.com
 The top level domain name is com
 The second level domain name is someaddress
 The third level domain name is www

12. Domain names
 What are some top level domain names?
 How many levels do there have to be?
 Does the lowest level domain have to be www?
 Are domain names case sensitive?
 What is the highest price paid for a domain name?

13. Domain names
 Host machines actually have IP (internet protocol)
addresses, not domain names.
 IP addresses have the form 255.255.255.255
 A series of Domain Name Servers keep lists which map
domain names to IP addresses.

14. Domain names
 Why bother with domain names?
 Why not just use IP addresses and save looking them
up?
 How can we easily find an IP address for a given
domain name and vice versa?

15. Parts of a URL
 The port specifies the port number that the
server is listening to for requests.
 Port number is optional
 If not given, the default of port 80 is used.

16. Port number
 Why use different port numbers?

17. Parts of a URL
 The exact path to the desired resource follows
the domain name (and port number if given).

18. Directory and resource path
 This is a description of the file structure on the host
system.
 If the host is Unix or Linux, this part of the URL is
case-sensitive.
 To avoid problems it is best to use lower case for all
resource paths, on all systems.

19. Directory and resource path
 Different levels of a path are always separated by
forward slashes, regardless of the host system.
 If multiple users are hosted on a system, the first part
of the path will be ~user

20. Directory and resource path
 The last part of the path is the actual resource desired,
usually an HTML page.
 The extension for HTML files can be .htm or .html
(recommended)
 If no resource is given, the server will try to display a
page named index.html. If not found, it may display a
directory listing, if permitted.

21. Directory and resource path
 A fragment identifier can be used to specify a given
part of an HTML page.
 E.g. the URL
http://www.someaddress.com/files/intro.html#part3
will show the page intro.html, starting with the section
labelled part3.
 This is useful for long documents.

22. Paths
Since graphics are not embedded in web pages,
the location of the graphic is indicated to the
web browser with a path in HTML.

23. Relative vs. absolute URLs
 In Unix terms what is the difference?
 In URL terms what is the difference?
 When are relative URLs used?
 Why?
 What problems can there be with use of relative URLs?

24. Packet switching
 Packet switching is one of the key concepts of the
Internet.
 This involves the use of two separate concepts, packets
and switching.

25. Packets
 A message is broken up into small pieces called
packets, usually about 1 kb in size.
 Each packet recieves a header containing the
destination IP address, the sender’s IP address, the
total number of packets that make up a message, and
the sequence number of that packet.

26. Switching
 Since the packets are individually addressed, and
numbered for sequence, they can be sent and received
in any order.
 This means that packets can be switched to different
routes to get to the destinations, according to network
traffic.

27. Request/Response
 The HTTP protocol is set up to work in terms of
requests and responses.

28. Request/Response
 In a typical WWW example, you type in a URL in your
browser’s location window, and press enter.
 Your browser then sends a message (request) to a web
server, asking for a given HTML page.
 The web server sends back the page, or a reason it
can’t comply (response).

29. A Typical Internet Request
1. You type in a URL in your web browser
(http://www.test.com)
2. The web browser needs to know the IP address that
is assigned to this URL, so it makes a request to a
Domain Name Server (DNS). The request gets
passed along from one name server to the next, until
the address is found, or the request times out.

30. A Typical Internet Request
3. Once the browser has the IP address
(123.456.789.123), it can prepare the HTTP request
packets and send them to the server.
4. The message is divided into packets, which can be
addressed with the source and destination IP
addresses.

31. A Typical Internet Request
5. The message packets are then sent on their way.
6. From a dial-up connection, the first step is the ISP.
7. The ISPs router looks at the destination address, and
if it can’t deliver the message, it passes it on to
another router, etc. until the message reaches its
destination.

32. A Typical Internet Request
8. The message reaches its destination site, usually a
web server, which processes the request. It then gets
the requested page, if available, and prepares a reply
message, including the requested information, and
then divides it into packets and sends it back to the
originator of the request.

33. Standards on the Internet/WWW
 Technical standards related to the Internet (e.g.
TCP/IP) are published as Requests for Comment
(RFCs). These are very technical, detailed descriptions
of the technology behind the Internet.
 URL - www.ietf.org

34. Standards on the Internet/WWW
 Standards related to the World Wide Web (e.g. HTML)
are set by the World Wide Web Consortium (W3C)
 URL – www.w3.org
 Standards released by the W3C are not necessarily
implemented completely or in the same way by
different web browsers.

35. Searching the web
 Search engines are necessary to even attempt to
catalogue the estimated 270,000,000 web sites, with an
estimated 7,000,000 being added daily.
 What are some popular search engines?
 How do they work?

36. IP addresses
 The current method of IP addressing uses 32 bit
addresses, and we are quickly running out of addresses
 Work is underway to introduce IPv6 or IPng, which
uses 128 bit addressing.

37. IP addresses
 This will provide
340,282,366,920,938,463,463,374,607,431,768,211,456
addresses, which could give up to
3,911,873,538,269,506,102 addresses per square metre of
the Earth’s surface.

38. Review
 What is the Internet?
 What is the WWW?
 Is email a part of the Internet?
 What are the parts of a URL?
 What are the parts of a domain name?

39. Review
 How does packet switching make Internet
communication more reliable?
 What organization makes decisions about HTML
standards?
 Are HTML standards always followed by the different
browsers?

40. Web browsers
A Web browser contains the basic software you need in order to find,
retrieve, view, and send information over the Internet.
This includes software that lets you:
Send and receive electronic-mail (or e-mail)
messages
worldwide nearly instantaneously.
Read messages from newsgroups (or forums) about
thousands of topics in which users share
information
and opinions.
Browse the World Wide Web (or Web) where you
can
find a rich variety of text, graphics, and interactive
information.

41. FTP/TELNET
TELNET: The Internet allows computers to converse with each other over
networks. A telnet program allows us to log into a distant computer
almost as if we were actually sitting physically at that computer.
FTP: File Transfer Protocol allows us to transfer files between two
different computers on the Internet.

42. TCP/IP
 TCP/IP, or the Transmission Control Protocol/Internet
Protocol, is a suite of communication protocols used to
interconnect network devices on the internet. TCP/IP
can also be used as a communications protocol in a
private network (an intranet or an extranet).


43. HTTP
 HTTP means HyperText Transfer Protocol. HTTP is the
underlying protocol used by the World Wide Web and this
protocol defines how messages are formatted and
transmitted, and what actions Web
servers and browsers should take in response to various
commands.
 For example, when you enter a URL in your browser, this
actually sends an HTTP command to the Web server
directing it to fetch and transmit the requested Web page.
The other main standard that controls how the World
Wide Web works is HTML, which covers how Web pages
are formatted and displayed.

44. POP
 On the Internet, a point-of-presence (POP) is an
access point from one place to the rest of
the Internet. (POP also stands for the e-mail Post
Office Protocol; see POP3.) A POP necessarily has
a unique Internet Protocol (IP) address. Your
Internet service provider (ISP) or online service
provider (such as AOL) has a point-of-presence on
the Internet and probably more than one. The
number of POPs that an ISP or OSP has is
sometimes used as a measure of its size or growth
rate.

45. SMTP
 SMTP is part of the application layer of the TCP/IP protocol. Using a
process called "store and forward," SMTP moves your email on and
across networks. It works closely with something called the Mail
Transfer Agent (MTA) to send your communication to the right
computer and email inbox.
 SMTP spells out and directs how your email moves from your
computer's MTA to an MTA on another computer, and even several
computers. Using that "store and forward" feature mentioned before,
the message can move in steps from your computer to its destination.
At each step, Simple Mail Transfer Protocol is doing its job. Lucky for
us, this all takes place behind the scenes, and we don't need to
understand or operate SMTP.

46. IMAP
 IMAP (Internet Message Access Protocol) is a standard email protocol that stores
email messages on a mail server, but allows the end user to view and manipulate the
messages as though they were stored locally on the end user's computing device(s).
This allows users to organize messages into folders, have multiple client
applications know which messages have been read, flag messages for urgency or
follow-up and save draft messages on the server.
IMAP can be contrasted with another client/server email protocol, Post Office
Protocol 3 (POP3). With POP3, mail is saved for the end user in a single mailbox on
the server and moved to the end user's device when the mail client opens. While
POP3 can be thought of as a "store-and-forward" service, IMAP can be thought of as
a remote file server.
Most implementations of IMAP support multiple logins; this allows the end user to
simultaneously connect to the email server with different devices. For example, the
end user could connect to the mail server with his Outlook iPhone app and his
Outlook desktop client at the same time. The details for how to handle multiple
connections are not specified by the protocol but are instead left to the developers
of the mail client.
Even though IMAP has an authentication mechanism, the authentication process
can easily be circumvented by anyone who knows how to steal a password by using
a protocol analyzerbecause the client’s username and password are transmitted as
clear text. In an Exchange Serverenvironment, administrators can work around this
security flaw by using Secure Sockets Layer (SSL) encryption for IMAP.

47. PING
 Ping is a basic Internet program that allows a user
to verify that a particular IP address exists and can
accept requests.
 Ping is used diagnostically to ensure that
a host computer the user is trying to reach is
actually operating. Ping works by sending an
Internet Control Message Protocol (ICMP) Echo
Request to a specified interface on the network and
waiting for a reply. Ping can be used for
troubleshooting to test connectivity and determine
response time.

48. Thank You