Understand the 7 OSI layers and their functions

Understand the 7 OSI layers and their functions

Understand the 7 OSI layers and explain their functions – The OSI layer is a standardized computer network protocol that enables different communication systems to communicate with one another. OSI was developed in 1977 by an international organization called the Organization for Standardization (ISO). OSI stands for Open Systems Interconnection.

OSI was created with the aim that different providers of network products worldwide can communicate with the same protocol. OSI has seven layers or so-called 7 OSI layers, with each OSI layer sequence having its own definition and mode of operation.

Understand the 7 OSI layers and their explanations

The OSI layer has 7 sequences from the application layer to the physical layer. For further details, you will find an explanation of the various OSI layers or the 7 OSI layers and their functions.

Layer 7 OSI layer

Layer 7: application layer

Application layer


The application layer or application layer is a term used to group protocols and procedures in architectural models of computer networks. Both the OSI layer and the TCP / IP models have an application layer.

The application layer acts as an interface to network-enabled applications, manages how applications get network access, and then generates error messages. The protocols on the application layer are HTTP, SMTP, FTP and NFS.

Level 6: presentation level

Presentation levels

The presentation layer is the sixth layer in the OSI layer open network reference model. On the presentation layer, the structure of the data obtained from the application layer is created in a format that can be transmitted over the network.

The presentation layer is responsible for performing data encryption, data compression, character set conversion (ASCII, Unicode, EBCDIC or other character sets), interpreting graphic commands and much more. The way this OSI layer works is to do the translation.

The presentation layer is used to translate the data to be transmitted by the application into a format that can be transmitted over the network. The protocols on this layer are redirector software such as the workstation service (in Windows NT) and the network shell.

Layer 5: session layer

Session shift

The session layer or session layer is the fifth layer of the network reference model of the OSI layer. This layer makes it possible to create or destroy connection sessions between nodes in a network.

The session layer defines how network connections can be created, maintained, or destroyed. Name resolution is also carried out in this layer.

Layer 4: transport layer

Transport layer

The transport layer is the fourth layer in the network reference model of the OSI layer that receives data from the session layer. This layer is responsible for providing reliable service for several overlying protocols.

The task of the transport layer is to split data into data packets and to assign serial numbers to these packets so that they can be rearranged when they arrive at their destination. In addition, this layer also makes a signal when the packet has been received successfully (acknowledgment) and sends the lost packet again in the middle of the road.

Layer 3: network layer

Network layers

The network layer is the third layer in the network reference model of the OSI layer. The network layer is responsible for the logical addressing and routing of packets through the network. Create and delete connections and connection paths between two nodes. Transfer data, establish reception and confirm and reset connection.

The network layer functions define IP addresses, create headers for packets, and then route them through internetworking using media routers and switches.

Layer 2: data link layer

Data transfer level

The data link layer or data link layer is the second layer from the bottom of the OSI layer model, which can convert network frames that contain error detection data and retransmit the failed frames.

The main task of the data link layer is to facilitate the transmission of raw data and then to convert this data onto a channel that has no transmission errors.

The data link layer determines how the data bits are grouped into a format called a frame. It also includes error correction, flow control, hardware addressing (MAC address), and determining how devices such as hubs, bridges, and repeaters are working.

This layer, based on IEEE 802 technology, is divided into two subordinate layers, namely the Logical Link Control (LLC) layer and the Media Access Control (MAC) layer.

Layer 1: physical layer

physical layer

The physical layer or physical layer is the first layer in the network reference model of the OSI layer, which is the lowest of the seven other OSI layers.

This layer defines the interfaces and mechanisms for placing data bits on a network medium such as cable, radio or light. In addition, this layer also defines the electrical current and voltage, the modulation, the synchronization between bits, the activation and disconnection of connections and some electrical properties for the transmission medium (UTP / STP cable, coaxial or fiber optic).

Functions of the physical layer for the definition of network transmission media, signaling methods, bit synchronization, network architecture (Ethernet or Token Ring), network topology and cabling. In addition, this layer also defines how the network interface card (NIC) can interact with wired or wireless media.

The last word

That is the meaning of the 7 OSI layers and an explanation of their functions. Based on the application layer, presentation layer, session layer, transport layer, network layer, security layer and bit transmission layer. That’s all for this article, I hope it’s useful.

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