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
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
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.
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.
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.