In the terminology of data communication or network protocols, there is one type of protocol, namely the OSI layers. This type consists of 7 layers that need to be understood, and each of these layers has its own definition, function, and advantages. Moreover, the way each layer works is also explained in detail.
For the OSI layers protocol type, there are indeed 7 layers in it. These layers form the OSI type along with their functions, namely as follows:
1. Physical
Physical is the 1st OSI Layer. The function of the physical layer is physical devices, media, and connectors related to the transfer of data that transmits bits (1 or 0). The physical layer functions to convert bits (1 or 0) into signals and send them through media such as copper cable transmission, optical fiber, or wireless. Based on the model, the function of this layer defines network transmission media, signaling methods, network topology, cabling, and building the network architecture itself.
Examples of devices at the physical layer: Hub, Repeater, Modem, RJ-45, Copper Cable, Fiber Optic Cable, and Antenna.
2. Data Link
Next, for the second layer is the data link, which functions to provide media using MAC addresses and can perform error detection. The task of this layer is to determine every data bit into a format called a frame.
Examples of devices at the data link layer: Switch, Bridge, and Access Point.
3. Network
The third layer is the network layer, which has the function and task of creating headers for packets containing IP information, both the sender IP and the recipient IP of the data. IP addressing is carried out with Internet Protocol (IP) such as IPv4 and IPv6. IP is a unique address that makes each device connected to the internet identifiable. The network layer also functions in routing and path determination.
Routing is the process of sending packets from the source to the destination based on IP addresses. Determining the best path for data transmission often uses protocols such as Border Gateway Protocol (BGP), Open Shortest Path First (OSPF), and Intermediate System to Intermediate System (IS-IS).
Examples of devices at the Network layer: Router, Firewall, and Gateway.
4. Transport
The 4th OSI Layer is Transport. The transport layer has the task of breaking data into several data packets, where the packets are given sequence numbers, and this process is called segmentation. The transport layer can provide transparent and reliable transfers. In fact, multiplexing, flow control, and error checking along with the correction method are also available.
Protocols can send their data packets and also ensure whether the packets are sent and received successfully, which means they reach the correct destination. Even if there is a packet loss or damage in the transmission process, everything can be controlled by retransmitting the packet.
Examples of devices at the Transport layer: Web/Application Server, Computer, Smartphone, Application Server, and IoT Devices.
Examples of protocols: TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
5. Session
The 5th OSI Layer is Session. There is still the session layer, where this layer briefly functions to separate data in various applications. Meanwhile, the next task as the fifth layer is to define a connection so that it can be created, managed, and developed. The session layer organizes and manages connections between two devices by enabling sending and receiving of data, including session opening and closing.
Examples of devices at the session layer: Video Conference Systems such as Zoom Room Hardware, Cisco Webex Room Kit, Microsoft Remote Desktop Services.
Examples of protocols in this model: NFS, SMB, Netbios, Netbeui, RTP, PAP, and ADSP.
6. Presentation
The 6th OSI Layer is Presentation. The presentation layer is the OSI Layer that functions to receive data from the application layer and convert it from binary form (1 or 0) into a format that can be read by humans. The data will also be encrypted and decrypted by the system.
Examples of devices at the presentation layer: Software.
Examples of protocols: MIME, SSL, redirector software, TLS, and many more.
7. Application
The 7th OSI Layer is Application. The application layer contains all the services or protocols needed by application software or operating systems to communicate over the network. The last layer, application layers, is the layer that becomes the center of interaction between the user and the applications that work with the function of a network. Another function is to configure how applications work using network resources.
If there is an error in the network configuration process in this layer, then the layer can provide a message.
Examples of services and protocols that apply: HTTP, SMTP, FTP, NFS, and several others.
It can be clearly seen all the functions and tasks performed by each of the 7 OSI layers mentioned above, where all of them indeed support a network protocol.
References
Amin, M. S., & Rahman, S. (2023, May). An introduction of Open System Interconnection (OSI) model and its architecture [Preprint]. ResearchGate. https://doi.org/10.20944/preprints202305.1858.v1
