7 OSI MODEL LAYER

                                                                    7 OSI MODEL 

APPLICATION LAYER

In the Application Layer, where the file that a student at Cobham College intends to publish into the Cobham College Online Learning System platform is delivered through data transit services like SMTP, POP3, and others. In this case, the file transfer protocol (FTP) is used to deliver the data.

End-user applications like web browsers and email clients operate at the application layer. It offers protocols that let computer programs transmit and receive data and provide consumers useful information. The Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), and Simple Mail Transfer Protocol are a few examples of application layer protocols (SMTP) and Domain Name System (DNS).

PRESENTATION LAYER

Taking care of the syntax and semantics of the information sent between two interacting systems is the main objective of this layer. It serves as a translator so that the two systems can communicate on the same channel and comprehend one another with ease. The presentation layer compresses multimedia data before transmitting it because the length of the data is very large and a lot of bandwidth will be needed to transmit it over media. The data is then divided into small packets, which will then be decompressed at the receiver's end to restore the original length of data in its original format. 

When data is received from the application layer by the student's computer (the sender), it is encoded, encrypted, and compressed before being sent to the session layer. The data from the session layer is received by the Online Learning System server (receiver), which then decodes it by conducting data translation, decryption, and decompression on the sender's data.

SESSION LAYER

By starting and ending sessions between end-user application processes, the session layer enables users on other machines to establish active communication sessions with one another. The session layer implements checkpointing, restart, and termination methods as well as full-duplex and half-duplex operations. This layer will add encryption on the sender's end and decode encryption on the receiver's end if the devices are communicating over an encrypted connection so that it can be presented as readable data. 

This layer handles authentication and reconnection in the event of a network failure in addition to supporting a number of connections. Data is then transferred to or from the Transport layer after the session has been formed. 

This layer will initiate the communication session from the student's computer's (sender) side by sending requests and responses between the application layer and transport layer to check the validity of the desired session. If the answer is yes, it will go on to the next tier. On the server (receiver) side of the online learning System, it will display the sender's request to access the system.

TRANSPORT LAYER

To ensure complete data transfers, the Transport Layer enables transparent data flow between end users. Within a tiered architecture of protocols and other network elements, it enables logical communication between application processes running on several hosts. TCP, UDP, DCCP, and SCTP are examples of transport-layer protocols that are used to regulate the amount of data transferred, where it is sent, and at what pace.

Additionally, the transport layer is in charge of handling mistake correction so that the user receives high-quality, dependable service. This layer is the part of the network that permits multiplexing and allows the host to transmit and receive data, packets, or messages over a network without experiencing any errors.

The transport layer receives the data from the higher layer and segments it at the student's computer (the sender). Before sending the data to the network layer, the header file of the data also contains the source and destination port numbers. Data reassembly and sequencing are carried out by the transport layer at the OnlineLearning System server's (receiver) side. The data is directed to the appropriate application when the port number is obtained from the header file.

NETWORK LAYER

The subnet is under the control of the network layer. Based on the service priority, network conditions, and other variables, it suggests the optimum route for moving data from the source to the destination. This layer's primary function is to transport packets across various networks from source to destination. A network layer is not required if two systems are linked by the same link. It serves as a network controller by directing the signal through various channels to the other end.

Additionally, it divides upgoing communications into a small number of packets and puts together coming packets into messages for higher levels. The routing issue in broadcast networks is straightforward. As a result, the network layer is frequently minimal or nonexistent.

The network layer splits the data segments received from the higher layer into smaller pieces known as data packets at the student's computer (sender) side. Similar to this, on the server (receiver) end of the OnlineLearning System, the data packets are split into segments for the transport layer. In the network layer, routers are primarily used for routing purposes. The Open Shortest Path First (OSPF), BGP (Border Gateway Protocol), IS-IS (Intermediate System to Intermediate System), and other protocols are some of the ones that are frequently used in this tier.

DATA LINK LAYER

The most dependable node-to-node data transport is performed by the data link layer. As a bridge between the Logical Link Control layer and the physical layer of the network, this layer is sometimes subdivided into sublayers called Media Access Control (MAC). and Logical Link Control (LLC), which is tasked with passing the packets to the Network layer of the receiver that is receiving. 

The data connection layer's primary goal is to turn a transmission facility's raw form into a line that appears error-free to the network layer. In order to complete this work, it divides the incoming data into data frames (usually made up of a few hundred or thousand bytes) and sends each frame one at a time. If the service is trustworthy, the recipient will authenticate the receipt of each frame by sending one back. The data link layer uses error detection bits and corrects the faults. 

Data is transferred to or from the Physical layer, the top layer in the OSI model, at the Data Link layer. The data is transferred from the network layer to the student's computer (the sender) in the form of packets, which are then divided into smaller units known as data frames. The data frame is changed into packets at the online learning System server's (receiver) side for the network layer.

PHYSICAL LAYER

The OSI reference model's Physical Layer is the base layer. The synchronization between the sender and the receiver is the subject of this. At the bit level, the sender and receiver are synced. This layer's data is a stream of bits. For transmission, the bits need to be encoded into signals. It specifies the type of encoding (for instance, how signals are made up of 0s and 1s). The transmission rate, or bits per second, is also specified at this layer. 

According to network specifications, this layer handles the majority of the network's physical connections, including wireless transmission, various connector types and standards, network interface cards, and more. However, it is not concerned with the actual physical medium, such as copper and fiber. 

The physical layer on the student's end will receive the data from the higher layer, transform it into bitstreams (0s and 1s), and deliver it through a physical channel. The bitstreams will be transformed into frames at the online learning System server and sent to the data-link layer.