To Initiate the Communication between different Computer in Network where each computer has their own network architecture for e.g. Windows and Linux having completely different architecture of network, OSI (Open System Interconnection). The are Seven Layer (Application Layer, Presentation Layer, Session Layer, Transport Layer, Network Layer, Datalink Layer and Physical) in OSI Model Where each layer perform the Tight Knit Principle (Protocol) and pass the data to next layer in performing the reliable communication.
Moving From Top to Down of Each Layer Pass the data to next layer and encapsulate and Ultimately Reaching to Physical Layer (Receiver) and Then the Receiver Decapsulate the Data Package from Bottom to Top layer (Physical Layer to Application Layer) and access the data.
In Application Layer, Network Application is Used for initiation of Communication such as Browser, Outlook etc. each of them uses the Protocol like HTTP/HTTPS, SMTP, FTP based on the data that needed to send. When passing the data to the Presentation Layer it converts it into the binary format and encapsulated Via SSL (Secure Socket Layer) and establish the Connection Between Client and Server. After the establishment then it passed to Transport Layer where the data are segmented and assigned the port number (For HTTP Port number is 80) to go through. Alongside it also adds the Sequence number for reordering the segment at the receiver ends. and checksum for error detection and to verify the data whether it was altered or not during the transmission.
In Network Layer of OSI Model Logical Addressing is a key function and it involves add the IP address of Source and Destination (either IPv4/ IPv6) to the data packet and it is encapsulated. It main object is to identify the Origination of data and enabling the reply to communication. Whereas in the Data Link Layer the Physical Address is assigned (MAC address of souce and destination), handle the creation of frames adding headers and trailers to the data. In headers it contains the physical addresses and other information. On the Trailer side it adds the error detection information commonly known as Cyclic Redundancy Check. Lastly, at the lowest layer of the OSI model, the Physical Layer is responsible for managing the transmission of data by converting binary sequences into signals—either analog or digital—which are then transmitted over the appropriate physical medium.