OSI Layer Model

OSI MODEL

    OSI model stands for Open System Interconnect that consists of 7 layers of computer systems that are used to communicate over a network. This model was introduced in 1983 by representatives of the major computer and telecom companies, and was adopted by ISO as an international standard in 1984 .

    In the OSI model there are 7 layers including physical layer, data link, network, transport, session, presentation and lastly the application layer. This can be seen in the diagram below. The OSI model can be described as "Top Down" from the application layer that directly serves the end user, down to the physical layer.

  

Layer 7 : Application Layer 

    End-user applications like web browsers and email programmes interact with the application layer. It establishes protocols that enable software to communicate and receive data as well as present users with useful information. Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), and Domain Name System are a few examples of application layer protocols (DNS).

    In this scenario, a student will use the UTeM network infrastructure to access the Online Learning system. As a result, the learner will be exposed to the website interface. The Applications layer provides this interface, which is the platform that allows students to log into the Online Learning system.

    The Application layer's major goal is to display received data and provide data exchange services to the user. Protocols are used to conduct data transmission and IP traffic traversal. When students try to contact the Online Learning system servers, they use HTTP, which is extensively used for data transfer on the Internet.

Layer 6: Presentation Layer

    Data is prepared for the application layer by the presentation layer. It specifies how data should be encoded, encrypted, and compressed between two devices so that it is correctly received on the other end. Any data transmitted by the application layer is prepared for transmission over the session layer by the presentation layer.

    This layer will standardise the information sent from the student's computer and, if necessary, finish the encryption process. When the data reaches the Online Learning system server, it will be decrypted. The data is encrypted and decrypted for security purposes. The data is then compressed to lower the number of bits in the information before being passed to the session layer. Compression will aid in the speed and efficiency of data uploading.

Layer 5: Session Layer

    The session layer establishes communication channels between devices, known as sessions. It's in charge of starting sessions, making sure they stay open and functional while data is transmitted, and terminating them after the connection is through. The session layer can also specify checkpoints during a data transfer, allowing devices to resume data transfer from the latest checkpoint if the session is stopped.

    When two systems, in this case the student's computer and the Online Learning System, desire to communicate, a session is created. The session layer will verify whether the application layer's request is available on the local or remote system. When a student asked for something. If the request is accessible in a distant system, it checks the network connection of the machine to see if it can access the resource.

    If the connection is unavailable, the application layer will issue an error message. However, it initiates a session with the distant system when a network connection is available. This session layer also terminates sessions whenever communication between two systems is unavailable, such as when a connection is lost or when a timeout occurs, as well as after the student has finished using the system.

Layer 4: Transport Layer

    On the transmitting end, the transport layer takes the data transferred in the session layer and divides it into "segments." It's in charge of reassembling the segments on the receiving end and converting them into data that the session layer may use. The transport layer handles flow control, which involves providing data at a pace that matches the receiving device's connection speed, as well as error control, which involves verifying if data was received wrongly and, if not, requesting it again.

    The transport layer will trace the student's communication between applications on the source and destination hosts based on the scenario given. It is the job of the Transport layer to maintain the different communication streams between these student and lecturer applications via internet segments. It will then split the data and organise it into application data streams. At the Transport layer, headers must be appended to each piece of application data to specify which communication is involved. Each piece of data may be forwarded to the appropriate application on the receiving host.

    These discrete pieces of data must also be reassembled into a complete data stream that the Application layer may use. The Transport layer protocols outline how the header information from the Transport layer is utilised to reassemble the data bits into streams that may be sent to the Application layer.

    The Transport layer must identify the target application in order to send data streams to the appropriate apps. The Transport layer does this by assigning an identifier to each application. This identifier is known as a port number in TCP/IP protocols. Each software process that requires network connectivity is given a port number that is unique to that host. This port number is used in the transport layer header to identify which application is responsible for that particular piece of data. The Transport layer connects the Application layer to the lower layer, which is in charge of network transmission. This layer accepts data from various discussions and sends it down to the lower layers in manageable chunks that can be multiplexed over the media.

    Furthermore, the lower layers are unaware that data is being sent across the network by different applications. They are in charge of delivering data to the proper device. After that, the Transport layer sorts the bits before delivering them to the correct application. There are various Transport layer protocols because different applications have different requirements. In order to be processed effectively in some applications, segments must arrive in a specific order.

Layer 3 : Network Layer

The network layer has two purposes. One method is to split segments into network packets and then reassemble them on the receiving end. The alternative method is to route packets across a physical network by determining the optimum path. To route packets to a destination node, the network layer utilizes network addresses (usually Internet Protocol addresses).

There is no need for a network layer if two computers (systems) are connected on the same link. It functions as a network controller and sends the signal across various channels to the other end. It also separates outgoing messages into packets and assembles incoming packets into higher-level messages. Because the routing challenge in broadcast networks is straightforward, the network layer is generally shallow or non-existent.

The data is sent from the student's computer to the Online Learning system. The information submitted by students is sent in packets to the IT centre for online learning. When the data arrives at the IT centre's Online learning, the packet is broken up into smaller pieces. When students want to send data, the network must be addressed by computer (IP Address) before the data can reach the IT centre, which uses a distinct LAN with UTeM campus network. The source of the data is the IP address, and the destination is Online learning at an IT centre.

Layer 2 : Data Link Layer

A connection between two physically connected nodes on a network is established and terminated via the data link layer. It divides packets into frames and sends them from one location to another. This layer is divided into two sections: LLC, which detects network protocols, does error checking, and synchronises frames, and MAC, which connects devices and defines permissions to transmit and receive data using MAC addresses.

In physical addressing, the data connection layer adds a header to the frame to specify the sender and receiver's physical addresses. The data link layer receives packets from the network layer and breaks them into digestible data units called frames, depending on the size of the NIC frames (Network Interface Card). When the student's computer and modem are connected to the same link, the data link layer provides a protocol to detect which device has control over the link at any given time.

Layer 1: Physical Layer

The physical layer is in charge of the network nodes' physical cable or wireless connections. It specifies the connector, the electrical cable, or the wireless technology that connects the devices, and is in charge of transmitting the raw data, which is just a series of 0s and 1s, while also controlling the bit rate.

In this project scenario, there are five network components that are used in the physical layer while delivering data to the next destination: NIC (1), wireless access points (1), modem (1), router (1), and switch (1). (1). The NIC (Network Interface Card) controls the exchange of data between the network and the user. In this situation, the network interface card (NIC) permits communication between the student's PC and the wireless access point. It allows a student's PC to connect to her WIFI via modem first, then via local area network (LAN).

When a student visits the Online Learning System's web page, his or her PC sends a request to the network card, which converts it into an electrical signal. Individual bits will be carried from one node to the next across the transmission media by this electrical signal. The bits will be delivered to the data connection layers through this mechanism. The data is delivered to the router via a coaxial cable network. Before the data is sent to the OUM network server and IT Centre, the router will send it to the cloud over the internet.

The data is received by the UTeM server via router over the internet, and it replies by sending the data back to the router for transmission to the IT Centre. As synchronisation of bits occurs in electrical signals, the IT Centre receives the data through the router and responds by sending the web page of the Online Learning System back to the network card. This signal is received by the NIC card, which then converts it into data that the student's PC can use to show the web page Online Learning System.