The document provides an introduction to the history and development of the Internet and World Wide Web. It discusses the origins of ARPANET in the 1960s, the development of protocols like TCP and IP, and the invention of the World Wide Web in the 1980s and 1990s which led to widespread commercial use of the Internet. It also summarizes key technologies and standards like HTML, HTTP, and the role of organizations like W3C.

1. INTRODUCTION TO INTERNET
TECHNOLOGY
1

2. History of the Internet and
World Wide Web
 ARPANET
 Implemented in late 1960’s by ARPA (Advanced
Research Projects Agency of DOD)
 Networked computer systems of a dozen
universities and institutions with 56KB
communications lines
 Grandparent of today’s Internet
 Intended to allow computers to be shared
 Became clear that key benefit was allowing fast
communication between researchers – electronic-
mail (email)
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3. History of the Internet and World
Wide Web (Cont.)
 ARPA’s goals
 Allow multiple users to send and receive info at same time
 Network operated packet switching technique
 Digital data sent in small packages called packets
 Packets contained data, address info, error-control info
and sequencing info
 Greatly reduced transmission costs of dedicated
communications lines
 Network designed to be operated without centralized
control
 If portion of network fails, remaining portions still able to
route packets
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4. History of the Internet and World Wide
Web (Cont.)
 Transmission Control Protocol (TCP)
 Name of protocols for communicating over
ARPAnet.
 Ensured that messages were properly routed
and that they arrived intact.
 Organizations implemented own networks
 Used both for intra-organization and
communication.
4

5. History of the Internet and World Wide
Web (Cont.)
 Huge variety of networking hardware and software
appeared
 ARPA achieved inter-communication between all
platforms with development of the IP
 Internetworking Protocol
 Current architecture of Internet
 Combined set of protocols called TCP/IP
 The Internet
 Limited to universities and research institutions
 Military became big user
 Next, government decided to access Internet for
commercial purposes 5

6. History of the Internet and World Wide
Web (Cont.)
 Internet traffic grew
 Businesses spent heavily to improve Internet
 Better service their clients
 Fierce competition among communications carriers and hardware
and software suppliers
 Resulted in massive bandwidth increase and plummeting costs
 Tim Berners-Lee invents Hyper Text Markup Language (HTML)
 Also writes communication protocols to form the backbone new
information system = World Wide Web
 Hypertext Transfer Protocol (HTTP)—a communications protocol
used to send information over the web
 Web use exploded with availability in 1993 of the Mosaic browser
 Marc Andreessen founds Netscape
 Company many credit with initiating the explosive Internet of
late 1990s. 6

7. World Wide Web Consortium (W3C)
 W3C Founded in 1994 by Tim Berners-Lee
 Homepage at www.w3.org
 Goals
 Internet universally accessible
 Standardization
 W3C Recommendations:
Technologies standardized by W3C
include the Extensible Hyper Text Markup Language (XHTML),
Cascading Style Sheets (CSS), Hyper Text Markup Language
(HTML—now considered a “legacy” technology) and the
Extensible Markup Language (XML).
not an actual software product, but a document that specifies a
technology’s role, syntax rules and so forth.
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8. Internet Explorer 7 Features
 Web browser
 Software that allows the user to view certain types of Internet files in an
interactive environment
 URL (Uniform Resource Locator)
 Each web page on the Internet has unique URL
 Usually begin with http-:// or https://
 Hyperlinks
 Visual elements on web pages that when clicked, load a specified web
document
 Images and text
 Can reference other web pages, e-mail addresses, files and more
 Download files
 Tabbed Browsing
 Allows the user to browse multiple pages without many windows
 Page Organization
 Using the History Feature
 List of previously visited URLs in chronological order 8

9. Internet Explorer 7 Features (Cont.)
 AutoComplete
 URLs from the history can be displayed in a drop-down list when a user
types a URL into the Address bar
 Off-Line Browsing
 Web pages can be saved directly to the computer’s hard drive for off-
line browsing
 Not connected to the Internet
 Downloads
 Files from the Internet may be copied to a computer’s hard drive
 Applications
 Plug-ins
 Extensions
 Viewing Source Code
 Understand how the programmer created the page
 Learn how to develop your own pages
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10. Search engines or Directories
• Most people are primarily interested in tools
for finding information on the World Wide
Web.
• Originally there were two kinds of search
services on the Web:
Directories
Engines
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11. Search directories
• Search directories are hierarchical databases with references to
websites.
• The websites that are included are hand picked by living human
beings and classified according to the rules of that particular
search service.
• Yahoo is the mother of all search directories. However, in order
to search the directory you must go to their special directory
page.
• Their regular search results are not fetched from the directory,
but from their search engine.
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12. Search directories (Continued)
• The first page normally gives you the most general categories
(like "Computers and Internet" or "Education").
• Click your way down the hierarchy to the right category, select
the website you find the most interesting and start reading.
• If you use the search form when exploring a directory, remember
that you are not searching the text of the actual web pages of a
particular site.
• Instead you are searching the text contained in the site title and
the description of the site.
• These are composed by the directory editors, and are often
based on suggestions from the site owners themselves.
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13. Search engines
• Search engines are -- well -- "engines" or "robots" that crawl the
Web looking for new web pages.
• These robots read the web pages and put the text (or parts of the
text) into a large database or index that you may access.
• None of them cover the whole Net, but some of them are quite
large.
• The major players in this field are Google, Yahoo! Search (which is
not the same as the Yahoo! Directory), Live Search and Ask.
• Search engines should be your first choice when you know exactly
what you are looking for.
• They also cover a much larger part of the Web than the
directories.
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14. A Communications Model
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15. The key elements of this model are:
• Source - generates data to be transmitted
• Transmitter - converts data into transmittable
signals
• Transmission System - carries data from source
to destination
• Receiver - converts received signal into data
• Destination - takes incoming data
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16. Communications Tasks
The key tasks that must be performed in a data communications system.
Transmission system utilization - need to make efficient use of
transmission facilities typically shared among a number of communicating
devices
A device must interface with the transmission system once an interface is
established, signal generation is required for communication
There must be synchronization between transmitter and receiver, to
determine when a signal begins to arrive and when it ends there is a
variety of requirements for communication between two parties that might
be collected under the term exchange management
Error detection and correction are required in circumstances where 16
errors cannot be tolerated

17. Communications Tasks
• Flow control is required to assure that the source does not overwhelm the
destination by sending data faster than they can be processed and absorbed
• Addressing and routing, so a source system can indicate the identity of the
intended destination, and can choose a specific route through this network
• Recovery allows an interrupted transaction to resume activity at the point of
interruption or to condition prior to the beginning of the exchange
• Message formatting has to do with an agreement between two parties as to
the form of the data to be exchanged or transmitted
• Frequently need to provide some measure of security in a data
communications system
• Network management capabilities are needed to configure the system,
monitor its status, react to failures and overloads, and plan intelligently for
future growth
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18. Data Communications Model
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19. Networking
• Growth of number & power of computers is
driving need for interconnection
• Rapid integration of voice, data, image & video
technologies
• Two broad categories of communications
networks:
– Local Area Network (LAN)
– Wide Area Network (WAN)
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20. Wide Area Networks
• Span a large geographical area
• Rely in part on common carrier circuits
• Alternative technologies used include:
– circuit switching
– packet switching
– frame relay
– Asynchronous Transfer Mode (ATM)
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21. Circuit Switching
• Uses a dedicated communications path
established for duration of conversation
• Comprising a sequence of physical links
• with a dedicated logical channel
• eg. telephone network
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22. Packet Switching
• Data sent out of sequence
• Small chunks (packets) of data at a time
• Each packet is passed through the network from node
to node along some path leading from source to
destination.
• At each node, the entire packet is received, stored
briefly, and then transmitted to the next node.
• Packet-switching networks are commonly used for
terminal-to-computer and computer-to-computer
communications.
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23. Frame Relay
• Developed to take advantage of high data rates and
low error rates on modern WAN links.
• Whereas the original packet-switching networks were
designed with a data rate to the end user of about 64
kbps, frame relay networks are designed to operate
efficiently at user data rates of up to 2 Mbps.
• The key to achieving these high data rates is to strip
out most of the overhead involved with error control.
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24. Asynchronous Transfer Mode
• ATM uses fixed-length packets, called cells.
• As with frame relay, ATM provides little overhead for error control,
depending on the inherent reliability of the transmission system
and on higher layers of logic in the end systems to catch and
correct errors.
• By using a fixed packet length, the processing overhead is reduced
even further for ATM compared to frame relay.
• The result is that ATM is designed to work in the range of 10s and
100s of Mbps, and in the Gbps range.
• ATM allows the definition of multiple virtual channels with data
rates that are dynamically defined at the time the virtual channel
is created.
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25. Local Area Networks
• Smaller scope
– Building or small campus
• Usually owned by same organization as
attached devices
• Data rates much higher
• Switched LANs, eg Ethernet
• Wireless LANs
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26. Metropolitan Area Networks
• MAN
• Middle ground between LAN and WAN
• Private or public network
• High speed
• Covers a larger area
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27. The Internet
• Internet evolved from ARPANET
– first operational packet switching network
– applied to tactical radio & satellite nets also
– had a need for interoperability
– led to standardized TCP/IP protocols
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28. Internet Elements
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29. Internet Architecture
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30. Example Configuration
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31. OSI Seven Layer Model
• The Open Systems Interconnection Reference Model (OSI Reference Model
or OSI Model) is an abstract description for layered communications and
computer network protocol design.
• It was developed as part of the Open Systems Interconnection (OSI)
initiative.
• In its most basic form, it divides network architecture into seven layers
which, from top to bottom, are the Application, Presentation, Session,
Transport, Network, Data-Link, and Physical Layers.
• It is therefore often referred to as the OSI Seven Layer Model.
• A layer is a collection of conceptually similar functions that provide services
to the layer above it and receives service from the layer below it.
• For example, a layer that provides error-free communications across a
network provides the path needed by applications above it, while it calls the
next lower layer to send and receive packets that make up the contents of
the path.
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32. 32

33. 33

34. Layer 1:Physical Layer
• Defines physical means of sending data over
network devices
• Interfaces between network medium and
devices
• Defines optical, electrical and mechanical
characteristics
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35. Layer 2:Data Link Layer
• Defines procedures for operating the
communication links
• Frames packets
• Detects and corrects packets transmit
errors
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36. Layer 3:Network Layer
• Determines how data are transferred
between network devices
• Routes packets according to unique
network device addresses
• Provides flow and congestion control to
prevent network resource depletion
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37. Layer 4:Transport Layer
• Manages end-to-end message delivery in
network
• Provides reliable and sequential packet
delivery through error recovery and flow
control mechanisms
• Provides connectionless oriented packet
delivery
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38. Layer 5:Session Layer
• Manages user sessions and dialogues
• Controls establishment and termination of
logic links between users
• Reports upper layer errors
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39. Layer 6:Presentation Layer
• Masks the differences of data formats
between dissimilar systems
• Specifies architecture-independent data
transfer format
• Encodes and decodes data; Encrypts and
decrypts data; Compresses and
decompresses data
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40. Layer 7:Application Layer
• Defines interface to user processes for
communication and data transfer in
network
• Provides standardized services such as
virtual terminal, file and job transfer and
operations
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41. Benefits of the OSI Model
• By separating the network communications into logical smaller
pieces, the OSI model simplifies how network protocols are designed.
• The OSI model was designed to ensure different types of equipment
(such as network adapters, hubs, and routers) would all be
compatible even if built by different manufacturers.
• A product from one network equipment vendor that implements OSI
Layer 2 functionality, for example, will be much more likely to
interoperate with another vendor's OSI Layer 3 product because both
vendors are following the same model.
• The OSI model also makes network designs more extensible as new
protocols and other network services are generally easier to add to a
layered architecture than to a monolithic one.
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