OSI MODEL

 

OSI LAYER MODEL

Figure 2: A layered framework use to communicate between all types of computers.

LAYER 7:  APPLICATION LAYER

                    Based on the project scenario, this application layer ensures an application can effectively communicate with other applications on different computer systems and networks. The lecturer sends data to students in the Online Learning System of Cobham College IT Center. The students received the data after this layer ensures it is identified, reachable, and ready to accept data. At this stage, the data or the application is presented in a visual form that the user can understand. Example HTTP, websites. It is giving permission to both students and lecturers to access the system. It also provides a layer that allows sending and receiving of data. If it is appropriate, it enables authentication between those devices for an extra layer of network security and ensures agreement at both ends on error recovery procedures. After that, the data will be specified and sent to the presentation layer.

LAYER 6: PRESENTATION LAYER

                  The OSI model's Presentation layer performs the simplest task of all its components. To assist the Application layer above it, syntactic processing of message data, such as format conversions and encryption/decryption, is handled at layer 6.

The syntax and semantics of the information transmitted between two systems are handled by the presentation layer. The data is then prepared for the application layer. It specifies how two devices should compress, encrypt, and encode data to ensure that it is correctly received on the other end. Any data transmitted by the application layer is processed by the presentation layer before being delivered via the session layer.

                   Assume you're ordering something from an internet store. These transactions are often conducted via secure transmission, which implies that any information going between the "store" or website application and the presentation layer must first be encrypted and then decrypted before being processed. This layer handles converting data from the top layer's application-format presentation to the required format and back again. Depending on whether the data is transmitted or received, the Presentation layer converts the data from one format to another before passing the information to the Session layer or the Application layer.

LAYER 5: SESSION LAYER

               The creation, management, and termination of connections between devices take place at the session layer, or layer 5. This layer enables various connections and is in charge of authentication and reconnection in the event of a network outage. Data then moves to or from the Transport layer after the session has been formed.

               Applications like live video and audio streaming that need precise data exchange typically employ the session layer. 

o   The session layer ensures that the connection is alive throughout the session

o   Secures the connection.

o   Dialogue synchronisation

o   Checking for connection failure

o   Reconnecting if the connection is lost

o   Ending communication,

      o    Specifying the timing and sequence of node communication

The session layer is in charge of notifying the client program that communication is terminated if the connection is lost or cannot be restored. Additionally, session layers would make sure that only nodes authorized for the session are connected.

LAYER 4: TRANSPORT LAYER

                The transport layer defines services to segment transfer, and reassemble the data for individual communications between the end devices. It describes general services and functions that provide ordered and reliable delivery of data between source and destination hosts and implements TCP and UDP protocols.

                 During this stage, the transport layer provides multiplexing enabling the host to send and receive error-corrected data through the implementation of TCP and UDP protocols. The flow and error control will be performed, and the data will be segmented and then broken up into packets at the network layer.

LAYER 3: NETWORK LAYER

                       The network layer controls the operation of the subnet. The main aim of this layer is to deliver packets from source to destination across multiple links (networks). If two computers(systems) are connected on the same link, then there is no need for a network layer. It routes the signal through different channels to the other end and acts as a network controller. It also divides the outgoing messages into packets and assembles incoming packets into messages for higher levels. In broadcast networks, the routing problem is simple. sp the network layer is often thin or even non-existent.

Functions of Network Layer

1. It translates a logical network address into a physical address. Concerned with a circuit, message, or packet switching.

2. Routers and gateways operate in the network layer. The mechanism is provided by the network layer for routing the packets to their final destination.

3. Connection services are provided including network layer flow control network layer error control and packet sequence control.

4. Breaks larger packets into small packets.

LAYER 2: DATA LINK LAYER

                  

                    The protocol layer in a program that manages the transfer of data into and out of a physical link in a network is called the data link layer. In the Open Systems Interconnection (OSI) architecture model for a collection of communication protocols, the data link layer is Layer 2. It is in charge of data delivery from node to node. Its main responsibility is to guarantee the delivery of information without errors. Additionally, DLL is responsible for encoding, decoding, and organizing incoming and departing data. This OSI model layer is said to be the most complicated because it conceals from the layers above all the hardware's inner workings.

                    The data link layer is concerned with the local delivery of frames between network nodes on the same level. These protocol data units, known as data-link frames, do not cross the boundaries of a local area network. Higher-layer functions such as inter-network routing and global addressing allow data-link protocols to focus on local delivery, addressing, and media arbitration. In this sense, the data link layer is analogous to a local traffic cop. It attempts to mediate between parties vying for access to a medium, regardless of their ultimate destination. Frame collisions occur when multiple devices attempt to use the same medium at the same time. Data-link protocols define how devices detect and recover from collisions, as well as mechanisms for reducing or preventing them.

data examples

LAYER 1: PHYSICAL LAYER

                    The first and lowest layer of the Open System Interconnection Model is the physical layer (OSI Model). The physical layer (also known as layer 1) handles bit-level transmission between devices and allows for electrical or mechanical interfaces to connect to the physical medium for synchronized communication. This layer manages the majority of the network's physical connections, including wireless transmission, cabling, cabling standards, and types, connectors and types, network interface cards, and more, as needed. The physical layer is not concerned with the actual physical medium, such as copper, fiber, and so on. The Physical Layer specifies the types of encoding (how the 0's and 1's in a signal are encoded). The Physical Layer is in charge of communicating unstructured raw data streams over a physical medium.