THE INTERNET
_____________
The Internet
• The Internet is a vast. worldwide
network that enables you to read the
latest news. to do research. to shop. to
communicate. to listen to music. to play
games. and to access a wide variety of
information.
• The Internet is unlike any previous
human invention.
• It is a world-wide resource, accessible
to all of the humankind.
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 collection of interconnected
networks – looks like a single, unified network
Internet Networking Protocols
Communications on the Internet is controlled by a set of two protocols:
TCP and IP
TCP/IP (1)
Transmission Control Protocol/Internet Protocol
• Networking protocol used by all computers and networks on the
Internet
• Originally developed by the US Department of Defense for Unix, but
now available for most other OSes
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, TCP reassembles
them into the original message
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 address even if the
given address is not precise. That is not the case for Internet
addressing
•216.239.33.101
DNS address
IP address
•www.google.com
IP Address
• 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
• 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
• Example:
• 192.168.1.33
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:
216.239.33.101 www.google.com
DNS: Domain Name System
• Domain names are the alias or English language equivalent of a computer’s
IP addresses
• Domain Name System (DNS) allows the use of easier to remember domain
names instead of IP addresses to locate computers on the Internet
• There is a DNS server at most ISPs. It converts the domain names in our
Internet requests to actual IP addresses
• In case it does not have a particular domain name in its table, it makes a
request to another DNS server on the Internet
Domain Names
Some of the top Level Domains
• .com – commercial/company site
• .edu/ac - educational/academic
• .gov – government site
• .org – non-profit organization
• .mil – military sites
• .int – international organizations
• .net – network providers
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.
https://en.wikipedia.org/wiki/Main_Page
• Before, going any further, let us dissect this URL
https://en.wikipedia.org/wiki/Main_Page
Protocol Server Directory &
Identifier Address File Name
How does the Web work?
User launches the browser on his/her computer
User’s
Computer
Browser
User types-in the URL into the browser
User’s
Computer
The browser breaks
User’s
down the URL Computer
https://en.wikipedia.org/wiki/Main_Page
Wiki/Main_Page
Directory &
File Name
en.wikipedia.org
https Server’s Name
Protocol
Identifier
Browser sends server’s name to the DNS server
Domain Name
User’s DNS
Computer Server
IP Address
Browser establishes a connection with the server
User’s
Computer
Internet
Web
Server
Browser sends a ‘GET’ request for wiki/Main_Page
User’s
Computer
Web
Server
Server sends the requested file to the browser
User’s
Computer
Web
Server
Browser displays Main_Page
User’s
Computer
X
Tools & Services Available on the Internet
• Electronic mail (POP, IMAP, SMTP)
• Instant messaging (ICQ, MSN)
• Remote login (telnet)
• File transfer (ftp)
• Network news (nntp)
• WWW (http)
Chronology of events that
led to today’s Internet
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
ARPANET continued to expand throughout the 70's and 80's
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) was introduced, standardizing the
transfer of files between networked computers
1980’s
1983 - The TCP/IP protocols became 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
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
Plus, NSF supported institutions (universities, etc.) in their efforts to
connect to the regional nets
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
1989 - The backbone network is upgraded to T1, making it able to
transmit data at speeds of 1.5 Mb/s (approx. 60 pages of text/second)
1990’s
1990 - The ARPANET is dissolved
1993 - CERN releases WWW, developed by Tim Berners-Lee
It uses HTTP and hypertext, revolutionizing the way info is presented &
accessed on Internet
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 Network Access Points
ANY QUESTIONS?
