Open Systems Interconnection OSI

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The OSI Layers

• Open Systems Interconnection OSI

2
Overview

• Provides a common basis for the coordination of
  standards development for the purpose of system
  interconnection, while allowing existing
  standards to be placed in perspective within the
  overall reference model.

3
OSI Seven Layer Model

• 7. Application
• 6. Presentation
• 5. Session
• 4. Transport
• 3. Network
• 2. Data link
• 1. Physical

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1. Physical

• Concerned with transmission of unstructured bit
  stream over physical medium deals with the
  mechanical, electrical, functional, and
  procedural characteristics to access the physical
  medium.

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2. Data link

• Provides for the reliable transfer of information
  across the physical link sends blocks of data
  (frames) with the necessary synchronization,
  error control, and flow control.

6
3. Network

• Provides upper layers with independence from the
  data transmission and switching technologies used
  to connect systems responsible for establishing,
  maintaining, and terminating connections.

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4. Transport

• Provides reliable, transparent transfer of data
  between end points provides end-to-end error
  recovery and flow control.

8
5. Session

• Provides the control structure for communication
  between applications establishes, manages, and
  terminates connections (sessions) between
  co-operating applications.

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6. Presentation

• Provides independence to the application
  processes from differences in data representation
  (syntax).

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7. Application

• Provides access to the OSI environment for users
  and also provides distributed information
  services.

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Overview OSI Model

• 7. Application
• 6. Presentation
• 5. Session
• 4. Transport
• 3. Network
• 2. Data link
• 1. Physical

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• Reference
• Data and Computer Communications
• W. Stallings
• Mac Graw Hill