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The concept of layers is used to describe communication
from one computer to another. shows a set of questions
that are related to flow, which is defined as the motion
through a system of either physical or logical objects.
several examples of flow and ways that the flow process
can be broken down into details or layers.
A conversation between two people provides a good
opportunity to use a layered approach to analyze
information flow. In a conversation, each person wishing
to communicate begins by creating an idea. Then a
decision is made on how to properly communicate the
idea. For example, a person could decide to speak, sing
or shout, and what language to use. Finally the idea is
delivered. For example, the person creates the sound
which carries the message.
This process can be broken into separate layers that may
be applied to all conversations. The top layer is the
idea that will be communicated. The middle layer is the
decision on how the idea is to be communicated. The
bottom layer is the creation of sound to carry the
communication. |
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The same method of layering explains how a computer
network distributes information from a source to a
destination. When computers send information through a
network, all communications originate at a source then
travel to a destination. The information that travels on
a network is generally referred to as data or a packet.
A packet is a logically grouped unit of information that
moves between computer systems. As the data passes
between layers, each layer adds additional information
that enables effective communication with the
corresponding layer on the other computer.
The OSI and TCP/IP models have layers that explain how
data is communicated from one computer to another. The
models differ in the number and function of the layers.
However, each model can be used to help describe and
provide details about the flow of information from a
source to a destination.
In order for data packets to travel from a source to a
destination on a network, it is important that all the
devices on the network speak the same language or
protocol. A protocol is a set of rules that make
communication on a network more efficient. For example,
while sailing a ship, sailors, obey very specific rules
for communication with other ships and traffic control.
A data communications protocol is a set of rules or an
agreement that determines the format and transmission of
data.
Layer 4 on the source computer communicates with Layer 4
on the destination computer. The rules and conventions
used for this layer are known as Layer 4 protocols. It
is important to remember that protocols prepare data in
a linear fashion. A protocol in one layer performs a
certain set of operations on data as it prepares the
data to be sent over the network. The data is then
passed to the next layer where another protocol performs
a different set of operations.
Once the packet has been sent to the destination, the
protocols undo the construction of the packet that was
done on the source side. This is done in reverse order.
The protocols for each layer on the destination return
the information to its original form, so the application
can properly read the data. |
