Transcript Document

Internet Overview
(Chapter 1 in [2])
Outline
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History of the Internet
Seven Layers of the OSI Model
TCP/IP and the OSI Model
History of the World Wide Web
World Wide Web Consortium (W3C)
Hypertext Transfer Protocol (HTTP)
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History of the Internet (1/5)
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ARPAnet
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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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History of the Internet (2/5)
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ARPA’s Goals
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Allow multiple users to send and receive info at same time
Network operated packet switching technique
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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
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If portion of network fails, remaining portions still able to route
packets
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History of the Internet (3/5)
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Transmission Control Protocol (TCP)
Name of protocols for communicating over
ARPAnet
 Ensured that messages were properly routed and
that they arrived intact
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Organizations implemented own networks
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Used both for intra-organization and
communication
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History of the Internet (4/5)
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Huge variety of networking hardware and software
appeared
 ARPA achieved inter-communication between all
platforms with development of the IP
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Internet 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
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History of the Internet (5/5)
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Internet traffic grew
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Businesses spent heavily to improve Internet
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Better service their clients
Fierce competition among communications carriers
and hardware and software suppliers
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Bandwidth (info carrying capacity) of Internet increased
tremendously
 Costs plummeted
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Seven Layers of the OSI Model (1/4)
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Seven Layers of the OSI Model (2/4)
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Physical layer
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Data-link layer
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Be concerned with transmitting raw bits over a
communication channel.
To take a raw transmission facility and transform it into a line
that appears free of undetected transmission errors to the
network layer.
Network layer
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Determining how packets are routed from source to
destination
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Seven Layers of the OSI Model (3/4)
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Transport layer
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To accept data from the session layer, split it up into
smaller units if need be, pass these to the network
layer, and ensure that the pieces all arrive correctly at
the other end.
Session layer
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It establishes, maintains, and synchronizes the dialog
between communicating systems. It also adds what
called synchronization points for backup delivery in
case of system or network failure.
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Seven Layers of the OSI Model (4/4)
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Presentation layer
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Be requested sufficiently often to warrant finding a
general solution for them, rather than letting each
user solve the problems. A typical example is
encoding data in a standard agreed upon way.
Application layer
The application layer contains a variety of protocols
that are commonly needed.
 File transfer, Email, WWW
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TCP/IP and the OSI Model (1/2)
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The TCP/IP is a suite or a stack of protocols
that officially controls the Internet. TCP/IP was
developed before the OSI model.
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TCP/IP and the OSI Model (2/2)
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History of the World Wide Web
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WWW
Allows computer users to locate and view
multimedia-based documents
 Introduced in 1990 by Tim Berners-Lee
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Internet today
Mixes computing and communications technologies
 Makes information constantly and instantly available
to anyone with a connection
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World Wide Web Consortium (W3C)
(1/2)
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W3C
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Founded in 1994 by Tim Berners-Lee
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Devoted to developing non-proprietary and interoperable
technologies for the World Wide Web and making the Web
universally accessible
Standardization
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W3C Recommendations: technologies standardized by W3C
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include Extensible HyperText Markup Language (XHTML),
Cascading Style Sheets (CSS) and the Extensible Markup Language
(XML)
Document must pass through Working Draft, Candidate
Recommendation and Proposed Recommendation phases before
considered for W3C Recommendation
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World Wide Web Consortium (W3C)
(2/2)
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W3C Structure
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3 Hosts
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Massachusetts Institute of Technology (MIT)
European Research Consortium for Informatics and Mathematics
(ERCIM)
Keio University of Japan
400 Members
W3C homepage at www.w3.org
W3C Goals
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User Interface Domain
Technology and Society Domain
Architecture Domain and Web Accessibility Initiatives
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Hypertext Transfer Protocol
(HTTP)
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Hypertext Transfer Protocol (HTTP) is a clientserver program for accessing and transferring
documents on the World Wide Web (WWW), a
collection of multimedia documents.
The Uniform Resource Locator (URL) is a
standard identifier for specifying information on
the Internet.
URL:
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