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1
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- Introduction to the seven layers
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2
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- OSI – Open Systems Interconnect
- The Model was developed in the early 1970s by the International
Standards Organizations (ISO). It provides a set of general design
guidelines for data-communications systems and gives a standard way to
describe how various portions (layers) communicate in a system
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3
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- The hierarchical layering of protocols on a computer that forms the OSI
model is known as a stack. A given layer in a stack sends commands to
layers below it and services commands from layers above it.
- The seven layers in order from highest to lowest are Application,
Presentation, Session, Transport, Network, Data Link, and Physical can
be remembered by using the following memory aide: All People Seem To
Need Data Processing .
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4
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- Imagine Interstate highways, and all of the standards that they are
built with, standard sizes, traffic flows, signs, etc. This reduces chaos and improves the
ability of auto manufactures…OSI does the same for the Information
highway, or networks.
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5
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6
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- Application Layer – Allows applications to use the network.
- Presentation Layer – translates data to ensure that it is presented
properly for the end user.
- Session Layer – works primarily at the beginning and ending of the
transmission
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7
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- Transport Layer – organizes segments for delivery, and segments and
reassembles packets as they are sent/received.
- Network Layer – main purpose is to decide the path the information
should follow
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8
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- Data Link Layer – provides a system through which network devices can
share a communication channel
- Physical Layer – the interface through which the data moves along the
network
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9
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- When data is sent, it works down the layers, travels along the physical
layer, and then travels up the layers… the information is contained by
headers, which separate the layers.
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