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What is OSI Model?


By Unblocked Hub

August 3, 2022

The OSI (Open Systems Interconnection) Model explains how applications communicate with each other over a network. The OSI Model consists of 7 layers. These layers are defined from the top layer down. (Application, Presentation, Session, Transportation, Network, Data Link, Physical)


These 7 layers are the operating system, network hardware, applications, fiber optic, wifi, etc. that enable transmission via ethernet. It is provided by a mix of network card drivers as well as wireless protocols.



    The top layer is the seventh (Application) layer. This layer is the layer where most users interact. This layer provides network services to the user. These services are http etc. These are protocols that work with the client's data. For example, http is used in web browsers such as Opera, Google Chrome, Microsoft Edge, Mozilla Firefox. Such applications provide a number of services to the end user.



    The sixth (Presentation) layer can exchange data with the application layer. The task of this layer is to convert data from one format to another, that is, into a format that the other computer can understand. For example, you became a member of a site. Data is converted from one format to another, encrypted and transferred to the presentation layer where it needs to be decoded and processed.



    The fifth (Session) layer performs the task of establishing and finalizing the application connection between two devices. This layer supports multiple connection types. It is also responsible for authentication and reconnection in case of connection loss. After the session is established, the data moves to the next layer.



    The fourth (Transport) layer is responsible for transporting data over the network. This layer handles things like at what speed, in what amount, where to send the data. These services can be provided via TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). After this layer completes its task, the data is transferred to the network layer.



    The third (Network) layer provides routing of data. This layer is used to send and receive data packets to the correct destination. The IP protocol operates at this layer. It also manages the mapping between logical addresses. This is done with ARP (Address Resolution Protocol). Then the data is transferred to the second layer.



    The second (Data Link) layer is divided into sublayers. These sub-layers are known as MAC (Media Access Control and LLC (Logical Link Control). The layer establishes a connection with the physical network. When this layer receives data from the physical layer, it first checks whether there is a transmission error in the data. Then it packages the bits into data frames. MAC and It manages physical addressing methods for LLC layers.An example of the MAC layer is the 802.11 frame type.



    The first (Physical) layer is the physical/electrical layer of the OSI model. This layer includes receivers, transmitters, network cables, radio frequencies, etc. Contains. Data is transmitted to the layer as bits. How can this data be transmitted via radio frequency, electrical signals, etc. It is determined that it will be converted.