Communications Technology
14.1 - Fundamental Network Models
When computers are connected together, a network is created. The
reason as to why we need to connect is to share data and resources, and
communicate with each other. There are three fundamental parts of the
network. These are known as the components of the network, which is,
the structure and the protocol. The protocol is important in effective
transfer of data, many protocols have been created to make sure that
thedata transfer is done ef iciently and securely. There are two core
network models that many networks are built upon. These include:
- Transmission Protocol/Internet Protocol (TCP/IP)
- Open Systems Interconnection (OSI) model
Both of them outline rules and standards about how communications
should take place over a network. Each is divided into several layers, the
OSI model has seven different layers which include:
- Application: This is the top layer of the model that directly interacts
with data from the user. Software applications, such as web
applications and email clients, rely on the applications layer to
communicate. However, user applications, such as word processing
applications, are not included in this applications. The application layer
is responsible for managing the protocols that allow meaningful data
to be presented by the user. It manages protocols such as HyperText
Transfer Protocol [HTTPS] and Simple Mail Transfer Protocol [SMTP]
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, - Presentation: The primary function of the presentation layer is to
prepare data ready for use in the applications layer. This could involve
the translation, encryption and compression of data. It makes sure that
the data is translated into a form that will be understood by the
receiving device. If the devices are communicating over a secure
connection, the data will be encrypted. It will also decrypt any data
that is received. It will also compress any data that is required to
increase the speed of transmission.
- Session: This layer is responsible for opening and closing
communication links between devices. The time that passes between
a communication link being opened and closed again is called
session. This layer makes sure that the session is open for long enough
to allow all the data to be transmitted and then closes it immediately,
as soon as transmission is completed
- Transport: This layer is responsible for breaking down the data from
the session layer into segments. It is also responsible for reassembling
the segments in the receiving device. This layer is also responsible for
low control and error checking. It checks that all the data has been
received and will request a retransmission if it is not complete.
- Network: The network layer breaks down the segment from the
transport layer into smaller units, known as packets. It is also
responsible for routing, which is the process of inding the best path
across the network. The network layer performs these tasks when data
is transmitted from network to network. A router is one of the key
network components in this layer.
- Data Link: This layer performs a very similar role to the network layer,
but rather than transmitting data from network to network, it is
responsible for transmitting data from node to node within a network.
It takes the packets created at the network layer and converts them
into frames. A switch is one of the main components of this layer.
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, - Physical: This layer involves the physical equipment that is used to
transmit data, such as the cables. In this layer, layer is broken down
into bits to be transmitted as binary. This layer is also responsible for
reassembling the bits into frames, after transmission.
The OSI model is a logical model that can be applied when creating a
network. An alternative setup is the TCP/IP model. In the most simplest
form, TCP/IP model is a condensed version of OSI model. It has 4 layers
which include:
- Application Layer: This layer condenses the role of the application,
presentation and session layers from the OSI model. It uses several
protocols to provide a standardized exchange of data. The protocols
this layer uses includes HTTP, SMTP, post of ice protocol [POP] and ile
transfer protocol [FTP].
- Transport Layer: This layer is comparable to the transport layer in the
OSI model. It is responsible for maintaining end to end
communications between devices. The are two fundamental
protocols used at this level which includes, transmission control
protocol and user datagram protocol.
- Network Layer: This layer can also be known as the internet layer and
it is comparable to the network layer in the OSI model. It breaks data
down into packets and transmits it network to network. There are two
fundamental protocols used at this level which includes, internet
protocol [IP] and internet control message protocol [ICMP].
- Link Layer: This layer can also be known as the physical layer and it
condenses the role of data link layer and physical layer from the OSI
model. A protocol used at this level is the address resolution protocol
[ARP].
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14.1 - Fundamental Network Models
When computers are connected together, a network is created. The
reason as to why we need to connect is to share data and resources, and
communicate with each other. There are three fundamental parts of the
network. These are known as the components of the network, which is,
the structure and the protocol. The protocol is important in effective
transfer of data, many protocols have been created to make sure that
thedata transfer is done ef iciently and securely. There are two core
network models that many networks are built upon. These include:
- Transmission Protocol/Internet Protocol (TCP/IP)
- Open Systems Interconnection (OSI) model
Both of them outline rules and standards about how communications
should take place over a network. Each is divided into several layers, the
OSI model has seven different layers which include:
- Application: This is the top layer of the model that directly interacts
with data from the user. Software applications, such as web
applications and email clients, rely on the applications layer to
communicate. However, user applications, such as word processing
applications, are not included in this applications. The application layer
is responsible for managing the protocols that allow meaningful data
to be presented by the user. It manages protocols such as HyperText
Transfer Protocol [HTTPS] and Simple Mail Transfer Protocol [SMTP]
f
, - Presentation: The primary function of the presentation layer is to
prepare data ready for use in the applications layer. This could involve
the translation, encryption and compression of data. It makes sure that
the data is translated into a form that will be understood by the
receiving device. If the devices are communicating over a secure
connection, the data will be encrypted. It will also decrypt any data
that is received. It will also compress any data that is required to
increase the speed of transmission.
- Session: This layer is responsible for opening and closing
communication links between devices. The time that passes between
a communication link being opened and closed again is called
session. This layer makes sure that the session is open for long enough
to allow all the data to be transmitted and then closes it immediately,
as soon as transmission is completed
- Transport: This layer is responsible for breaking down the data from
the session layer into segments. It is also responsible for reassembling
the segments in the receiving device. This layer is also responsible for
low control and error checking. It checks that all the data has been
received and will request a retransmission if it is not complete.
- Network: The network layer breaks down the segment from the
transport layer into smaller units, known as packets. It is also
responsible for routing, which is the process of inding the best path
across the network. The network layer performs these tasks when data
is transmitted from network to network. A router is one of the key
network components in this layer.
- Data Link: This layer performs a very similar role to the network layer,
but rather than transmitting data from network to network, it is
responsible for transmitting data from node to node within a network.
It takes the packets created at the network layer and converts them
into frames. A switch is one of the main components of this layer.
f f
, - Physical: This layer involves the physical equipment that is used to
transmit data, such as the cables. In this layer, layer is broken down
into bits to be transmitted as binary. This layer is also responsible for
reassembling the bits into frames, after transmission.
The OSI model is a logical model that can be applied when creating a
network. An alternative setup is the TCP/IP model. In the most simplest
form, TCP/IP model is a condensed version of OSI model. It has 4 layers
which include:
- Application Layer: This layer condenses the role of the application,
presentation and session layers from the OSI model. It uses several
protocols to provide a standardized exchange of data. The protocols
this layer uses includes HTTP, SMTP, post of ice protocol [POP] and ile
transfer protocol [FTP].
- Transport Layer: This layer is comparable to the transport layer in the
OSI model. It is responsible for maintaining end to end
communications between devices. The are two fundamental
protocols used at this level which includes, transmission control
protocol and user datagram protocol.
- Network Layer: This layer can also be known as the internet layer and
it is comparable to the network layer in the OSI model. It breaks data
down into packets and transmits it network to network. There are two
fundamental protocols used at this level which includes, internet
protocol [IP] and internet control message protocol [ICMP].
- Link Layer: This layer can also be known as the physical layer and it
condenses the role of data link layer and physical layer from the OSI
model. A protocol used at this level is the address resolution protocol
[ARP].
f f
