OSI and TCP/IP Model

OSI and TCP/IP Model

OSI and TCP-IP are network models used today.

 So why is a model needed? 

The answer is actually very simple. It is to package and transmit data circulating on the Internet within a certain rule. In this way, devices communicate with each other in a regulated and controlled manner.

1) As you can see, the OSI model consists of 7 layers.

2) The full expansion of OSI = Open Systems Interconnection

3) Today, more and more TCP-IP models are used.

4) In the picture, the right side shows the layers and the left side shows the protocols used in these layers.

Hardware (Physical) Layer:

1) Another name for the hardware layer is the physical layer.

2) The resolution of the bits is done in this layer.

3) Decoded bits are sent in two ways. In analog or signal form. This layer makes the decision of this shipping method.

4) There are also transfer modes of data. These are called half-duplex, full-duplex or simplex. This layer also determines the decision of this transmission mode.

Datalink Layer:

1) It works to detect errors that occur at the hardware layer.

2) The most important task of this layer is assigned to establish and terminate connections between physically connected (wired or wireless) devices.

3) Data flow control is done in this layer.

4) The most important done MAC for this layer is IEEE 802.2

Network layer:

1) In this layer, the best path selection is made for the data to reach the target.

2) Router works in this layer.

3) There is no guarantee that the data will be transmitted securely. But if we want, we can ensure to move the data securely. (IPsec)

4) Each device gets a credential in its own network. We call this IP. IPv4 and IPv6 operate at this layer.

5) The most important thing is that the control of whether the data reaches the other party in a complete manner is not done in this layer.

Transport Layer:

1) It transmits the information from the upper layer to the lower layers.

2) It controls the flow of the data and whether it reaches it completely.

3) The packaging process takes place in this layer. In other words, the large data coming from the upper layer is divided into smaller data in this layer and sent to the receiver on the opposite side.

4) With ICMP, information is exchanged about whether the packets have been received from the other party. If there is a missing package, information is given with ICMP and the missing package is requested from the other party.

5) Protocols used here are TCP or UDP.

Session Layer:

1) Controls connections between devices.

2) It can establish, manage and terminate local or remote connections when the time comes.

3) Socket opening is also the task of this layer.

4) SQL and NFS can be used in this layer.

Presentation Layer:

1) It brings the data into a format that applications can accept.

2) It takes part in the conversion of data formats to each other.

Application Layer:

1) It is the layer with which the end-user interacts.

2) User-interactive applications are used in this layer. For example, protocols such as HTTP, SMTP are given as examples.

Summary of OSI Layers:

• Application: User interactive applications are in this layer.

• Presentation: Conversion of data formats to each other is in this layer.

• Session: Socket opening or login is the task of this layer.

• Transport: Error and flow control is done in this layer.

• Network: End-to-end communication and virtual addressing (IP) is done here.

• Data: Access to the media is done in this layer.

• Physical: This is the layer where the cables work.

1) It consists of only 4 layers.

2) TCP = Transmission Control Protocol

3) We can say that it forms the basis of the current internet.

Application Layer:

1) The application that wants to send data and the file format used are determined in this layer.

2) It provides communication between applications.

3) The application layer interacts with the transport layer via ports.

Transport Layer:

1) This layer decides how to send the data. Will it be sent with a UDP packet or a TCP packet?

2) It provides end-to-end data flow and control.

3) It doesn't care which switch or router it goes through.

4) The only task of this place is to check whether the package has reached the other side safely.

Internet Layer:

1) In this layer, the destination and source IP addresses are included in the packets.

2) The name of the resulting packages is DATAGRAM.

3) It is the task of this layer to direct the data from source to destination. So, which router and switch it will pass through is the responsibility of this layer.

4) Routing algorithms are also used for this routing.

Network Access Layer:

1) It is responsible for transforming the data into 1 or 0.

2) Protocols such as Ethernet, ATM take place in this layer.

3) Packages are called FRAME.

4) MAC addresses are put into frames.

COMPARISON OF TCP-IP AND OSI MODEL