Introduction to Internet
Contents
• What is Internet
• Some key concepts
• Internet history, Internet Services
• World Wide Web, types of web sites
• Internet and Libraries
• Example applications at NCSI, IISc
• Internet Resources: Examples
What is Internet?
• Interconnection of computers and
computer networks using TCP/IP
communication protocol
• Transport Control Protocol/ Internet
Protocol (TCP/IP)
• What is a protocol?
– A protocol is a set of rules defining
communication between systems
What is Internet?
• Intranet: Use of TCP/IP to connect
computers on an organizational LAN
• Internet: Use of TCP/IP to interconnect
such networks
• TCP/IP is the basic Internet protocol
• Various application protocols operate over
TCP/IP
– SMTP (E-Mail), HTTP (Web), IRC (Chat), FTP
(File transfer), etc.
• Internet consists of many
different types of networks
– Ethernet
– Token ring
How’s the
weather in
Seattle, Mar?
kashaw@cs.stanford.edu
Ethernet
• Different types of operating
systems and other software
• How do they work together?
Network
– Standards
Tokenring
MSN Messenger
mar@cs.washington.edu
Divide Work into Layers
Application
HTTP, SMTP, FTP,
TELNET, DNS
01010
End-to-End
TCP, UDP
Network
IP
Link Level
Ethernet, token ring

0 1 0 1 0
01010
make network simple and reliable
a
connect segments, address (locating
points on graph) and route (navigating
graph)
01010
01010


physically encode bits on “wire”
b
Sending Data Along Wires
• Connection-oriented
– Circuit switched
• Persistent connection set up between sender and
receiver
– Example: telephone system
• Connectionless
– Packet switched
Message
H
Data
H
Data
H
• Data partitioned into packets and
sent individually from sender to receiver
• Reassembled at receiver
Data
H
Data
TCP/IP
• Rules for information exchange between
computers over a network
• ‘Packet’ based – segment/ de-segment
information
• Client-Server (Request/ Response)
– Web browser (client), Website (Server)
• TCP – Handles data part
• IP – Handles address part – Identification of
every computer on the Internet – IP address
Internet – Some Key Concepts
• Backbone network
• Client/ Server
• IP Address
• Host name/ Domain name
– www.ncsi.iisc.ernet.in 144.16.72.150
• URL: Uniform Resource Locator
– Address for identifying a resource on a host with a
specific protocol
– access protocol://host.domain [:port]/path/file name
(Ex.: http://www.ncsi.iisc.ernet.in/ncsi/database.html)
Comparison of Switching Technologies
Circuit switched
• Advantages
– Only route once
– Latency and bandwidth
constant
• Disadvantages
Packet switched
• Advantages
– Efficient use of wires
– Small startup
overhead
– Idle resources unavailable• Disadvantages
for other connections
– Route each packet
– Large setup time
– Per packet overhead
– Single point of failure
• Distributed state
Ethernet
• Bob Metcalfe at Xerox PARC
• Used for local area networks (LANs)
– Physically near one another
– 200 computers within 100 meters
• Broadcast medium
– Single wire connects all computers
• Each computer has unique 48-bit MAC address
– All computers constantly listen
• “Carrier Sense, Multiple Access with Collision
Detect”
– Sender waits until wire unused before sending
– If hears collision, stops, waits random time, retransmits
Ethernet
Ethernet Variations
Ethernet Properties
•
•
•
•
Shared
Distributed (not Centralized)
Insecure
Unpredictable Latency & Bandwidth
Alternative to Ethernet:
Token Ring
• Alternative introduced by IBM (1980s)
• “Passing the Conch Shell”
Applications of the Internet
• Traditional core applications:
Email
News
Remote Login
File Transfer
• The killer application:
World-Wide Web (WWW)
• New applications:
Videoconferencing
Telephony
P2P applications
Internet Broadcast
Time Line of the Internet
Aug-01
Aug-99
Aug-97
Aug-95
Aug-93
Aug-91
Aug-89
Aug-87
Aug-85
Aug-83
Aug-81
Number of Hosts on the Internet
Growth of the Internet
1000000000
100000000
10000000
1000000
100000
10000
1000
100
Internet Infrastructure
Regional
Network
Backbone Network
Regional
Network
IXP
local ISP
IXP
Backbone Network
local ISP
Regional
Network
local ISP
IXP
corporate
network
Regional
Network
campus
network
Internet Infrastructure
• The infrastructure of the Internet consists of a
federation of connected networks that are each
independently managed (“autonomous system”)
– Note: Each “autonomous system may consist of
multiple IP networks
– Autonomous systems have a number (AS number)
• Hierarchy of network service providers (NSPs)
– Tier-1: nation or worldwide network (US: less than 20)
– Tier-2: regional networks (in US: less than 100)
– Tier-3: local Internet service provider (in US: several
thousand)
Internet Infrastructure
• Location where a network (ISP, corporate
network, or regional network) gets access to the
Internet is called a Point-of-Presence (POP).
• Locations (Tier-1 or Tier-2) networks are
connected for the purpose of exchanging traffic
are called peering points.
– Public peering: Traffic is swapped in a specific
location, called Internet exchange points (IXPs)
– Private peering: Two networks establish a direct link
to each other.
Topology of a Tier-1 NSP
Organization of a single node in a Tier-1 network
....
Peering points
Leased links
to customers
3Com
Bay Networks
Modem Bank
Modem Bank
Modem Bank
Modem Bank
Leased links
to customers
Leased links
to customers
Bay Networks
SD
3Com
....
3Com
Modem Bank
....
Links to other
nodes of the
network
....
SD
....
3Com
Dial-up and
leased links
to customers
Metropolitan
area networks
Who is Who on the Internet ?
•
•
•
•
•
Internet Society (ISOC): Founded in 1992, an international nonprofit professional
organization that provides administrative support for the Internet. Founded in
1992, ISOC is the organizational home for the standardization bodies of the
Internet.
Internet Engineering Task Force (IETF): Forum that coordinates the development
of new protocols and standards. Organized into working groups that are each
devoted to a specific topic or protocol. Working groups document their work in
reports, called Request For Comments (RFCs).
IRTF (Internet Research Task Force): The Internet Research Task Force is a
composed of a number of focused, long-term and small Research Groups.
Internet Architecture Board (IAB): a technical advisory group of the Internet
Society, provides oversight of the architecture for the protocols and the
standardization process
The Internet Engineering Steering Group (IESG): The IESG is responsible for
technical management of IETF activities and the Internet standards process.
Standards. Composed of the Area Directors of the IETF working groups.
Internet Services
• E-Mail
– One-to-one
– One-to-many (e.g. discussion forums)
• Telnet – remote login (e.g. library catalogue
access)
• FTP: File transfer (e.g. software packages)
• Web (HTTP): Hypertext linking/navigation
• IRC: Internet Relay Chat
• Internet telephony, mobile access, etc.
IISc
World Wide Web (WWW)
• “Killer Application”
• Hypertext linking of multi-media documents
• “Point and Click”
• Lingua-franca of Web: HTML
• Websites: Host multimedia documents, linked
using HTML (web pages)
• Web browsers: Access websites, “browse”
• Medium for Publishing, distributing, and
accessing information UNIQUE!
Growth of the Web
• Web is the totality of web pages stored on web servers
• Spectacular growth in web-based information sources
and services:
– Education and research
– Entertainment
– Business and commerce
– Personal home pages
• Estimated to contain several billion documents
• Doubling each year
• Over a billion web sites
• Almost every telephone owner – Internet user
Types of Websites
• Shopping sites
– www.amazon.com (book store)
– www.garden.com (gardening)
– www.indiabookshop.com (book store)
– www.shopperstop.com (clothes, etc.)
• Community sites
– www.acs.org (American Chemical Society)
– www.indiatimes.com
– www.gardencityinfo.com (Bangalore)
– www.nse-india.com (stock traders
Types of Websites
• Entertainment sites
– disney.go.com (Walt Disney)
– www.starwars.com
– www.carnaticmusic.com
– www.indiatalkies.com
• Identity sites
– www.ibm.com
– www.wipro.com
– www.iisc.ernet.in
Types of Websites
• Learning sites
– www.digitalthink.com (web-based training in IT)
– www.netskills.ac.uk (Internet training)
– www.nationalgeographic.com
• Information sites
– www.computers.com
– www.eb.com (Encyclopaedia Britannica)
– www.thomasregister.com
– www.timesofindia.com
Finding Information on Web
• Search Engines
– General
– Meta search engines
– Domain specific
• Directories
– General (e.g. Yahoo)
– Subject/Resource specific gateways (e.g.
EEVL)
Internet & Libraries
• Provide access to Internet resources
– Gateway services
• Electronic publishing and provision of L&I
services over intranet/ Internet
– OPAC, Portals, Digital Libraries
• Library administration and management
– Acquisition, Technical processing, etc.
• Professional self-learning