ISO – OSI MODEL

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					ISO – OSI MODEL
        +
 TCP/IP MODEL
    Prepared By K. Clark
        For use with
     AK ITEC 1010.30
       All copyright reserved
International Standards Organization
                  -
     Open Systems Interconnect


     Defines layers, or functions, that
      facilitate connectivity between
            different computers.
Seven Layers to OSI Model
  1.   Application Layer
  2.   Presentation Layer
  3.   Session Layer
  4.   Transport Layer
  5.   Network Layer
  6.   Data Link Layer
  7.   Physical Layer
    OSI Application Layer

Purpose: To handle communication
between applications. Data is sent to
the correct port, according to the
application, such as ftp, http, snmp.
User-based network applications
operate at this level.
      OSI Presentation Layer

Purposes:
1: To encode information into a format
    understandable by the other computer.
    May involve encryption.
2: To manage file level security.
    Example: file locking.
       OSI Session Layer


Purpose: To manage communications,
including logon-logoff procedures.
Transmission error-checking also occurs
here.
   OSI Transport Layer


Purpose: To define data packets,
including packet level error-
checking
   OSI Network Layer


Purpose: The routing, switching,
and control of information packets
through the network. Uses the
logical address to determine where
to send.
         OSI Data-Link Layer
Purposes: to prepare data at the bit level ,
   including addressing and bit-level error
   checking.
Two sublayers:
1. Logical Link Control – connects Network Layer
   with access method (eg: Ethernet).
2. Media Access Control – handles details of type of
   media, such as co-axial, fibre optic, etc.
    OSI Physical Layer


    Purpose: Manage the actual
 transmission according to type of
connection and topography in use.
Physical and Data-link layers interact
           to some degree.
            The OSI Layer Tree
                    H   Application Layer    T

                H       Presentation Layer       T

            H             Session Layer              T

        H                Transport Layer                 T

    H                    Network Layer                       T

H                       Data Link Layer                          T

                         Physical Layer
Transmission Control Protocol
              /
     Internet Protocol


  Defines layers, or functions, that
   facilitate connectivity between
         different computers.
     “Language of the Internet”
              TCP/IP Model
• Designed Before OSI model was published
• Based on U.S. DoD model
• Four levels roughly equivalent to OSI
  Seven levels.
  –   Application Layer
  –   Transport Layer
                                        Learn !
  –   Network (Internet) Layer
  –   Network Interface or Link Layer
TCP/IP Application Layer

Combines functions of OSI Model
   -     Application Layer
   -     Presentation Layer
   -     Session Layer
TCP/IP Transport Layer


Equivalent to OSI Transport Layer
  TCP/IP Internet Layer

Equivalent to OSI Network Layer
TCP/IP Network Interface Layer



  Combines Functions of OSI
     -     Data-Link Layer
     -     Physical Layer
The TCP/IP Layer Tree
        Original Data (file)
          Application Layer

            Transport Layer

      Internet or Network Layer

   Network Interface or Link Layer
Recommended Reading:
   TCP/IP JumpStart
   by: Andrew Blank
   pub: Sybex, 2000
   ISBN: 0-7821-2644-8
                       End !!



Slide Set Created September, 2003
Modifications: June, 2004, October, 2007

				
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