CS1010 Introduction to Computing
Lecture 18
Today’s Goals
(Introduction to the Internet)
• To become able to appreciate the role of the
Internet in today’s computing
• To become familiar with the history and
evolution of the Internet
• To look at several services provided by the
It belongs to …
Mr. Tom Peters of
After the accident, Mr. Peters …
filled out a form, giving info about:
– Himself
– The circumstances of the accident – Estimated repair expenses
1/
7
2/
7
3/
7
Claims processing in Lahore
5/
7
6/
7
7/
7
Key Question!
Answer: Everybody Wins!
• Tom Peters
Answer: Everybody Wins!
• Tom Peters
• ACME Insurance
• Bhola eServices
Lower premium &
Answer: Everybody Wins!
• Tom Peters
• ACME Insurance • Bhola eServices
Answer: Everybody Wins!
• Tom Peters
• ACME Insurance
• Bhola eServices
The Key Point …
Bhola eServices (Pvt) Ltd is … … supplying a service
… using local, attractively-priced workers … to a remote, overseas client
… over the Internet
Internet
:
What else does
the Internet
What Else?
• Enables users located at far-way locations to easily
share information with others located all over the world
• Enables users to easily and inexpensively
communicate with others located all over the world
• Enables the users to operate and run programs on
The Internet is unlike
any previous human
invention. It is a
world-wide resource,
accessible to all of
Internet Users Worldwide
2.4B in 2012
10.8M
Internet users in Pakistan in
5/2012
(
10%
of population)
In early 2012,
82
% of
Australian
population
75
% of
Singaporean
population
80
% of
Japanese
population
Key Characteristics (1)
Geographic Distribution
Global - reaches around the world
Robust Architecture
Adapts to damage and error
Speed
Key Characteristics (2)
Universal Access
Same functionality to everyone
Growth Rate
The fastest growing technology ever
Freedom of Speech
Promotes freedom of speech
The Digital Advantage
Internet: Network of Networks
• A large number of networks, interconnected
physically
• Capable of communicating and sharing data
with each other
• From the user’s point view, Internet – a
Intranet
An intranet is a network based on TCP/IP protocol (an internet) belonging to an
Internet Networking Protocols
Communications on the Internet is controlled by a set of two protocols:
TCP/IP (1)
Transmission Control Protocol/Internet Protocol
• Networking protocol used by all computers and
networks on the Internet
• Originally developed by the US DoD for Unix, but
TCP/IP (2)
Transmission Control Protocol/Internet Protocol
• TCP breaks down the message to be sent over the
Internet into packets
• IP routes these packets through the Internet to get
them to their destination
• When the packets reach the destination computer,
Tools & Services Available on the Internet
• Electronic mail (POP, IMAP, SMTP)
• Instant messaging (ICQ, MSN, Skype)
• Remote login (telnet) • File transfer (ftp)
• Voice over internet protocol (voip)
1960's
1969 - DoD-ARPA creates an experimental network – ARPANET – as a test-bed for emerging
networking technologies
ARPANET originally connected 4 universities &
enabled scientists to share info & resources across long distances
40
1970's
Networking tools developed in the 70's include:
1972 - The National Center for Supercomputing Apps. (NCSA) develops the telnet application for
remote login, making it easier to connect to a remote computer
1973 - FTP (File Transfer Protocol) is introduced,
1980's
1983 - The TCP/IP protocols becomes the only set of protocols used on the ARPANET
This sets a standard for all networks, and generates the use of the term Internet as the net of nets
ARPANET splits into two nets to keep military &
non-military network sites separate: ARPANET and
1980's
In 1982 and 1983, the first desktop computers
begin to appear
Many are equipped with an OS called Berkeley Unix, which includes networking SW, allowing
easy connection to the Internet using telnet
1980's
1985-86: NSF connects the US’s six
supercomputing centers together, calling it the the NSFNET, or NSFNET backbone
To expand access to the Internet, NSF developed
regional nets, which were then connected to the NSFNET backbone
1980's
1987 - NSF awards a grant to Merit Network, Inc. to operate & manage future development of the
NSFNET
Merit collaborates with IBM & MCI on R&D for fast networking technologies
1990's
1990 - The ARPANET is dissolved
1991 - Gopher is developed.
It provides a hierarchical, menu-based method for
providing & locating info on the Internet
1993 - CERN releases WWW, developed by Tim Berners-Lee
1990's
1993 - The NSFNET is upgraded to T3 (45 Mb/s or about 1800 pages/s)
1993-1994 - Web browsers Mosaic & Netscape Navigator are introduced
Their GUI makes WWW & Internet more appealing to the general public
1995 - NSFNET is replaced by a new architecture, called vBNS which utilizes regional networks and
Who runs the Internet
?
Internet Addressing
• Regular post cannot be delivered unless we write a
destination address on the envelope
• Same is true for the Internet
• Regular post can be delivered at the intended
180.150.151.104
www.uol.edu.pk
IP Address (1)
• A unique identifier for a computer on a TCP/IP
network
• Format: four 8-bit numbers separated by periods.
Each 8-bit number can be 0 to 255
• Example:
IP Address (2)
• Networks using TCP/IP route messages based on
the IP address of the destination
• Any IP addresses (as long as they are unique) can
be assigned within a Private Network
• However, connecting a Private Network to the
?
server
Client/Server Structure of the
Web
• Web site is a collection of files that reside on computers,
called Web servers, that are located all over the world and are connected to each other through the Internet.
• When you use your Internet connection to become part of the Web, your computer becomes a Web client in a worldwide client/server network.
Domain Names
• IP addresses are fine for computers, but difficult to
recognize and remember for humans
• A domain name is a meaningful, easy-to-remember
‘label’ for an IP address
• Examples:
180.150.151.104 www.uol.edu.pk
• A fully qualified domain name can be made up of a
top level domain (TLD), second level domain (SLD).
• Seven popular Top Level Domains are:
.com, .edu, .org, .gov, .net, .countryname, .int
• SLDs represent the name of a company/institution/
entity
• Subdomains represents the functional unit of a
cs . uol . edu . pk
Sub
DNS: Domain Name System (1)
• DNS is the way that Internet domain names are
located & translated into IP addresses
• Maintaining a single, central table of domain
name/IP address relationships is impractical
– Billions of DNS-IP translations take place every day
Internet Services
There are many, but we will look at only the following:
• FTP
• Telnet • Web • eMail
FTP: File Transfer Protocol
• Used to transfer files between computers on a TCP/
IP network (e.g Internet)
• Simple commands allow the user to:
– List, change, create folders on a remote computer
– Upload and download files
• Typical use: Transferring Web content from the
Telnet Protocol
• Using Telnet, a user can remotely log on to a
computer (connected to the user’s through a TCP/IP
network, e.g. Internet) & have control over it like a local user, including control over running various programs
• In contrast, FTP allows file operations only
The Web
• The greatest, shared resource of information
created by humankind
• A user may access any item on the Web through a
URL, e.g.
http://www.uol.edu.pk/cs/index.html
http://www.uol.edu.pk/cs/index.html
Protocol Identifier
Server Address
What is the World Wide Web?
• A huge resource of information
• Logically unified, but physically distributed
• Logically unified: Any one from any where can
access the information using a very simple scheme
consisting of links & URLs
• Physically distributed: The information is stored on
What is a Web site?
• A collection of related documents available on the
Web
• The first portion of the URLs in the Web pages of a
Web site is the same e.g.
– http://www.uol.edu.pk/ – http://www.uol.edu.pk/cs
– http://www.uol.edu.pk/cs1010
What is a URL?
• Uniform Resource Locator
• The unique address assigned to each unique
Examples
http://dawn.com
http://www.uol.edu.pk/cs
User’s
Computer
User launches the browser on his/her computer
User’s
Computer
User’s
Computer
The browser breaks down the URL
User’s
Computer
DNS Server
Browser sends server’s name to the DNS server
User’s
Computer
Web
In ter net
User’s
Computer
Web Server
User’s
Computer
Web
User’s
Computer
Browser displays index.html
• Computer-to-computer messaging
• Inexpensive, and quite quick, but not instant!
• The most popular service on the Internet, even
more than surfing, but soon to be overtaken by instant messaging
But first, the components:
• eMail client
• SMTP server
eMail Clients
• Programs used for writing, sending, receiving, and
displaying eMail messages
SMTP: Simple Mail Transfer Protocol
POP3: Post Office Protocol
• A protocol used for receiving eMail messages
• A POP3 server maintains text files (one file per user
account) containing all messages received by a user
• eMail client interacts with the POP3 server for
• To use pop3 server, you must have an account
on it, it prepares a text file (1 text file per user, all messages that arrived are stored in same text file)
• Email client talk with pop3 server, search for
Sender’s Computer
The message is prepared using the eMail client
Sender’s Computer
SMTP Server
Sender’s Computer
SMTP Server
POP3 Server
Sender’s Computer
POP3 Server
The receiver picks it at his/her convenience
Receiver's Computer SMTP
Sender’s Computer SMTP Server SMTP Server In ter net
Sender’s Computer
SMTP Server
POP3 SMTP
Sender’s Computer SMTP Server POP3 Server SMTP Server
The receiver picks it at his/her convenience
The Trouble with eMail
• Slow response times
• No way of knowing if the person we are sending
eMail to is there to read it
• The process of having a conversation through eMail
by exchanging several short messages is too
cumbersome
Instant Messaging
• The IM services available on the Internet (e.g. ICQ,
AIM, MSN Messenger, Yahoo! Messenger) allow us
to maintain a list of people (contacts) that we interact with regularly
• We can send an instant messages to any of the
Using Instant Messaging (1)
• Whenever a contact in our list comes online, the IM
client informs us through an alert message and by playing a sound
• To send an instant message to a contact, just click
Using Instant Messaging (2)
• The selected contact will receive that message
almost immediately after you press ‘Enter’
• When the contact’s IM client receives the message,
Using Instant Messaging (3)
• That contact then can type a response to the
received message, and send it instantly
• Several such conversations can be carried out
VoIP: Voice over IP
• Voice delivered from one device to another using
the Internet Protocol
• Voice is first converted into a digital form, is broken
down into packets, and then transmitted over a TCP/IP network (e.g. Internet)
• Four modes: – C2C
– C2T – T2C
Pro
Much cheaper than traditional phone service
Con
Noticeably poor quality of voice as compared with land-line phone service, but not much
What is a Web Search Engine?
• Search engines continuously scan the Web and compile a
list of all the Web pages that they find
• The search engine with the largest such list (or index) is
Google – with a list of over 2 billion Web pages and over
330 million images
• We use the search engine by typing a “search key word” or
Today’s Goal:
Introduction to the Internet
• We looked at the role Internet plays in today’s
computing
• We reviewed some of the history and evolution
