The 7 Layers of the OSI Models: Network Communication

The 7 Layers of the OSI Models: Network Communication

The 7 Layers of the OSI Models: Network Communication - The OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, proceeding to the bottom layer, over the channel to the next station, and back up the hierarchy.

OSI Models

Application (Layer 7)

This layer supports application and end-user processes. Communication partners are identified, quality of service is identified, user authentication and privacy are considered, and any constraints on data syntax are identified. Everything at this layer is application-specific. 

This layer provides application services for file transfers, e-mail, and other network software services. Telnet and FTP are applications that exist entirely at the application level. Tiered application architectures are part of this layer.

Function

As a means of collecting information and data sent over the network. When the user receives data (receiver/recipient) then the application layer will collect all the data that has arrived and then appear in certain applications. 

Vice versa, when the user sends data, the application layer will collect all the data in a particular application, and then forward the data to the presentation layer to be defined and processed further into the network. As a user interface for displaying data and information. 

After the presentation layer presents the data, the application layer will work in displaying the data presented in a user interface (can be an application, program, or certain systems), so that the data presented can be seen and observed directly by the user.

Presention (Layer 6)

This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa. The presentation layer works to transform data into the form that the application layer can accept. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. It is sometimes called the syntax layer.

Function

• Encrypt data or messages. The data encryption process is a process carried out to secure the data and messages to be transmitted to maintain the security of the message or data. When acting as a receiver, the presentation layer has a function to describe, which is to open the encryption of a message or data.
• Perform compression and decompression processes. The compression process is the process of compacting or shrinking data so that the data can be easily forwarded into a network. The decompression process is carried out to open and clarify the data that will be received and will be forwarded to the application layer. This process occurs when the presentation layer layer receives data that will be displayed on the application layer (user process as data receiver).
• Perform the process of formatting on graphic forms. Some data is transmitted in graphical form, or some applications require that data be displayed in graphical form, and vice versa. the function of the presentation layer is to format the graphic forms that enter the network.
• Translating data. This translation process is carried out so that any data or content transmitted over the network can be identified and defined by each layer in the OSI layer model and understood by the entire network.
• Presenting data. Helping present the existing data, both when it will be displayed into the application layer, and when it will be forwarded to the session layer layer.
• Define the data type. Determine the type of data to be transmitted, either transmitted to the application layer, or transmitted to the session layer. Several types of data types defined by this presentation layer are data types in the form of images, videos, and also text, and encryption codes for data.
  

Session (Layer 5)

This layer establishes, manages, and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.

Function

Communicating on a network. A network is a form of communication between computers. In order to build communication, a layer is needed that can process the communication system that exists between all the computers. Relationship formation. 

If the session layer has succeeded in establishing communication between computers in a network, then the task of the next session layer is to establish a relationship between each computer. Transfer and exchange of data. 

When communication occurs between computers in a network, then at that time there is a data transmission process, which is nothing but a form of data exchange process in a network. Termination in a network. Disconnect and terminate the connection in a computer network connection. Types of communication at the session layer: simplex, half-duplex, and full-duplex.

Transport (Layer 4)

This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.

Function

• Receive data from the session layer. The first function of this transport layer is to receive data sent through the session layer.
• Breaking data into smaller parts.
• Breaking data or data packets into smaller packets. This process is carried out to facilitate the process of sending alias data transmission that runs on the computer network. With this data splitting process, it is believed that any data will not be corrupted or experience a very slow transmission process due to the large size of the data.
• Forward data to the network layer to be given a header (title).
• Ensure that all data can arrive at the destination correctly.
• Sending a segment from one host to another host The next function of the transport layer is to process the segment delivery from one host to another host. segment itself is part of the data fragments that have been processed in the transport layer. That way, each piece of data will later be received on another host.
• Ensure data reliability. Reliability is a condition where data is true and contains according to specifications. The job of the transport layer is to ensure this. So, the transport layer will check whether the data that is processed and also processed in the transport layer is appropriate and reliable. When this is done, the transport layer will then send the data fragments or data packets to the next layer for further processing.
• Manage traffic from a network and set the traffic speed of data transmitted through a computer network. This is done so that every rotation and traffic can run and be transmitted smoothly and is also applied to prevent congestion when the network is in a very congested condition and has the potential to experience network congestion.
  

Network (Layer 3) 

This layer provides switching and routing technologies, creating logical paths, known as virtual circuits, for transmitting data from node to node. Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling, congestion control, and packet sequencing.

Function

Defines IP addresses. Determines the route to be taken during the journey by using routers and layer 3 switches. Maintain traffic queues on the network.

• Protocols at this layer are: Routing, IP
• Network layer device: Router

Data Link (Layer 2)

At this layer, data packets are encoded and decoded into bits. It furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control, and frame synchronization. The data link layer is divided into two sublayers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control, and error checking.

Function

Serves to determine how the data bits are grouped into a format called a frame. Error correction, flow control. Hardware addressing (as in Media Access Control Address (MAC Address) Determines how network devices such as hubs, bridges, repeaters, and layer 2 switches operate.

• The protocols in this layer are LLC and MAC, 802.3 CSMA/CD (Ethernet), 802.4 Token Bus (ARCnet), 802.5 Token Ring, and 802.12 Demand Priority.
• The devices are Bridges, Switches, and NIC / LAN Card.

Physical (Layer 1)

This layer conveys the bit stream - electrical impulse, light, or radio signal -- through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier, including defining cables, cards, and physical aspects. Fast Ethernet, RS232, and ATM are protocols with physical layer components.

Function

Responsible for processing data into bits and transferring them over media, such as cables, and maintaining physical connections between systems. Move bits between devices.

• Protocols at the physical layer are Organizations: IEE, TIA/ETA, ANSI, etc. Cable (ie. RJ45)
• The devices are Hubs, NICs (Layers 1 & 2), Media: Coax, Fiber, Unshielded Twisted Pair, Wireless.