ppt on topic internet

1. THE INTERNET

2. The Internet
• The Internet: An internet that spans the world
– Original goal was to develop a means of connecting
networks that would not be disrupted by local disasters.

3. The Internet
• An information system
• Communication tool
• A large network of computer systems
world wide
• can be explored by using a Web Browser
• Services available through the Internet:
• Email (Discussion groups , Chat Rooms, etc.)
• Information search (including research)
• Education (Online courses; virtual colleges)
• Entertainment, News, and more…...

4. Internet Architecture
• Internet Service Provider (ISP)
• Access ISP: Provides connectivity to the Internet
– Traditional telephone (dial up connection)
– Cable connections
– Wireless

5. Internet Composition

6. A network protocol
Is the set of very detailed rules, sequences, message
formats, and procedures that computer systems use
and understand when exchanging data with each
other.

7. Examples of Protocols
– Transmission Control Protocol (TCP)
– User Datagram Protocol(UDP)
– File Transfer Protocol (FTP)
– Hypertext Transfer Protocol (HTTP)
– Simple Mail Transfer Protocol (SMTP)

8. Transmission Control Protocol (TCP/IP)
• It is connection oriented.
• It establish connection before data transfer
• It divide the whole message in small parts known as
packets
• It sends packets in order and it also receive in order
in destination

9. User Datagram Protocol(UDP)
• It is not connection oriented.
• It does not establish connection before data transfer
• It divide the whole message in small parts known as
packets.
• It sends packets to the available path on that
particular movement.
• The packets are not received in order and it required
a addition mechanism for ordering the packets on
destination.

10. File transfer protocol
• Is a network protocol used for transfer data from one
computer to another through a network such as
Internet (is commonly used for copying files to and
from other computers)
• FTP is a two-way system - it can be used to copy or
move files from a server to a client computer as well
as upload or transfer files from a client to a server
• FTP systems generally encode and transmit their
data in binary sets which allow for faster data
transfer

11. What is an IP Address?
• An IP address is a unique global address for a
network interface
– An IP address:
- is a 32 bit long identifier
- encodes a network number (network
prefix) and a host number.

12. Network prefix and host number
• The network prefix identifies a network and the host
number identifies a specific host (actually, interface
on the network).
network prefix host number

13. Dotted Decimal Notation
• IP addresses are written in a so-called dotted
decimal notation
• Each byte is identified by a decimal number in the
range [0..255]
• Example:
10000000 10001111 10001001 10010000
1st Byte
= 128
2nd Byte
= 143
3rd Byte
= 137
4th Byte
= 144
128.143.137.144

14. IP Addresses (continued)
• When IP addresses were originally created, they
were called classful addresses
– That is, each IP address fell into particular class
– A particular class address has a unique network address
size and a unique host address size
– There are basically five types of IP addresses: Classes A,
B, C, D and E
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15. IP Addresses (continued)
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16. IP Addresses (continued)
• When you examine the first decimal value in the
dotted decimal notation:
– All Class A addresses are in the range 0 - 127
– All Class B addresses are in the range 128 - 191
– All Class C addresses are in the range 192 – 223
– All Class D addresses are in the range 224 – 239
– All Class E addresses are in the range 240 - 255
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17. Name servers

18. DNS
• IP addresses are difficult to remember
– JohnDoe@140.203.8.22 would be difficult to remember
– If JohnDoe’s mail server moves to another machine, then his e-mail address
would not be valid anymore
– Something like JohnDoe@wuzwuz.ucg.ie would be appropriate
• Need some mechanisms to translate wuzwuz.ucg.ie to the IP address
– To solve this problem DNS was invented
• It is a hierarchical, domain-based naming scheme and a
distributed database system for implementing naming scheme.
• Usage:
– Map name onto an IP address, an application program calls an library
procedure, called resolver.
– The resolver sends packet to a local DNS server which looks up the name and
returns the IP address to the resolver
– The resolver returns the IP address to the application, which can establish an
TCP/IP connection with the destination (or send packets)

19. URL – Uniform Resource Locator

20. URL – Uniform Resource Locator

21. Traditional Internet Applications
• Electronic Mail (email)
– Domain mail server collects incoming mail and transmits
outgoing mail
– Mail server delivers collected incoming mail to clients
via POP3 or IMAP
• File Transfer Protocol (FTP)
• WWW (World Wide Web)

22. World Wide Web (WWW)
– a vast collection of information that’s connected like a
web
– accessible through the Internet using connections called
hyperlinks
– view the WWW resources through a program called a
Web Browser, such as:
• Netscape Navigator
• Internet Explorer
– Navigate through the WWW by pointing to and clicking on
hyperlinks (underlined or boldfaced words, phrases,
icons, or images)
– Also called Cyberspace or the Information Superhighway

23. Architectural Overview
• Browser displays a page on the client machine
– Click on a link, the browser sends a message to the abcd.com web server asking it for the
page
– When page arrives, it is displayed; if it contains a hyperlink on a page on xyz.com, that is
clicked, then the browser will send a message to xyz.com server and the process
continues

24. HTML – HyperText Markup
Language
• (a) HTML source code
– Markup language containing explicit commands for formatting
• (b) Formatted page