ISOOSI Reference Model

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ISO/OSI Reference Model

• Best tool for people learning about sending and
  receiving data on a network

Nancy Nakakura
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Background

• International Organization for Standardization
  (ISO)
• Researched proprietary and non-proprietary
  networks
• Developed by ITUTT (International
  Telecommunications Union Telecommunication)
• Open Systems Interconnection (OSI)
• 1984

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What the OSI provided Vendors

• Standards ensuring greater compatibility and
  interoperability between the various types of
  network technologies in existence

TCP/IP
IBMS SNA
DECNET
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Why a Layered Model?

• Reduces Complexity
• One big into 7 Smaller
• Facilitates modular engineering
• Assures interoperable technology
• Accelerates evolution
• Simplifies teaching and learning

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Advantage

• Best tool to us learn about SENDING data
• and
• RECEIVING data on a network

Protocols
Communication
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Not tangible.Conceptual framework

• Cannot touch
• Network functions that occur at each layer

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1 Physical Layer

• Bits (0 and 1) converted
• electrical current
• light pulses
• Carries signals that transmit data generated by
  higher layers
• Examples of devices
• Repeater
• Hub
• Network Media (cables)

11101011
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2 Data Link

• Defines how network layer packets are transmitted
  as bits
• Bridges (traffic cop)
• MAC Address (12 bits)
• NIC Card
• Frame (header trailer)

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3 Network Layer

• Defines how info from transport layer is sent
  over networks
• Defines how hosts are addressed
• IP Addresses
• Router

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4 Transport Layer

• Takes care of data transfer
• Checks integrity of data if desired by upper
  layers
• TCP and UDP operate at this layer

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5 Session Layer

• Establishes and terminates connections
• Arranges sessions to logical parts
• TCP and RPC provide some functions at this layer

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6 Presentation Layer

• Responsible for protocol conversion
• Networks translator
• Manages data compression to reduce number of bits

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7 Application Layer

• Defines protocols used between application
  programs
• Email Protocols take place
• SMTP
• FTP
• Telnet

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As information to be sent descends through layers
of a system, it looks less and less like human
language and more and more like 1s and 0s that
the computer understands
10001111000101110100110101110001000110000111.
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How Layers Are Grouped
Host Layers Provide accurate data delivery
between computers
Media Layers Control physical delivery of
messages over the network
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Devices Function at Layers
NIC
IP Addresses Router
Mac Address NIC Frame Bridge
Repeater Hub Network Media
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Away Pizza Sausage Throw Not Do Please
Anything People Sales Tell Not Do Please
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Simply. A model is a way of picturing how
information travels through networks