DATA COMMUNICATION AND NETWORKING (GROUP 9)

PROJECT SCENARIO

        The Figure 1 shows the logical network flow from a home network to Cobham College facilities. In this figure, a Cobham College’s student is trying to access the Online Learning system located in the Cobham College network facilities. The student is using her modem to connect to the public network before able to connect to the Cobham College facilities. From the Cobham College network, the data then was forwarded to IT Center where the Online Learning System server is located.

(7 LAYERS OF OSI MODEL )

     The International Organization for Standardization formally established the OSI model layer, which stands for open system interconnect, in 1984. An important reference tool for comprehending data communication between any two networks is the OSI diagram. Because networking is complicated, the OSI model breaks down the intricate operations of computer networks into seven distinct layers.

     The seven layers that make up the OSI model are as follows physical layer, data connection, network, transport, session, presentation, and application layer. In order to transport human-readable information from one device to another end device, data must pass through all seven OSI levels.

1) APPLICATION LAYER

The protocols used for process-to-process communication are found in the application layer. The protocol outlines the format and control data necessary for standard Internet operation.

In this case, a student must log in to the Cobham College campus network facilities' Online Learning system. The student will therefore view the website's user interface. The Applications layer offers this interface, which is the platform needed for students to log into the Online Learning system. Displaying the information that has been received and offering user-facing data exchange services are the primary goals of the application layer. Protocols are used to manage data transfer and traversing IP traffic. The protocol used by students to connect to the servers of the online learning system is HTTP, which is widely utilised throughout the World Wide Web for data transfer.

2) PRESENTATION LAYER

The presentation layer ensures the information that the application layer of one system sends out is readable by the application layer of another system. In this layer, the information sent from the student’s computer will be standardized and the process of encryption will be completed if needed. Next, it will decrypt when the data arrives at Online Learning system server. The encryption and decryption of the data are for privacy and security purposes. Then, this layer will compress the data to reduce the number of bits contained information and it will pass to the session layer. Compression helps to increase the speed and efficiency of uploaded data.

3) SESSION LAYER

The session layer is the fifth layer that are responsible for maintains, establishes, and synchronizes the interaction between communication systems. This session allows a process to add checkpoint to steam of data and dialog control.

A session is created when two system which are student’s computer and Online Learning system in this scenario want to enter dialog. This layer will check the request made by application layer is available in local system or in remote system when a student made any request. If the request is available in remote system, it test the availability of the computer’s network connection to access the resource. If the network connection is available, it establishes a session with remote system. But when the connection is not available, it will form the application an error message. This layer also terminate session if the communication is not available between two systems such as disconnected or timeout and also when the student finish accessing the system.

4) TRANSPORT LAYER

Because it builds on the network layer, which is essential for providing data transfer from a process on a source system to a process on a destination machine, the transport layer is known as the heart of the OSI layer. On the transmitting end, this layer accepts the session layer's data transfers and divides them into "segments" so that the session layer can once again utilise the data. Additionally, it is hosted on one or more networks. In other terms, the transport layer coordinates data transfers between hosts and end systems. The Transport Layer also decides where, at what rate, and how much data should be transported. The messages obtained from the Application Layer are built upon in this layer. Additionally, it aids in ensuring the orderly and error-free delivery of data units. Through flow control, error control, and segmentation or desegmentation, it manages the dependability of a link.

 This layer also provides a confirmation of a successful data transmission and sends the subsequent data if there were no problems. The Transmission Control Protocol (TCP), which is constructed on top of the Internet Protocol (IP), often known as TCP/IP, is an example of a transport layer protocol. Port numbers for TCP and UCP operate at Layer 3, or Network Layer. As a result, routers at this layer aid in the efficient performance of their duties. The data segmentation and control required may be reassembled by the Transport Layer into different communication streams. The student's communication between programmes running on the source and destination hosts will be monitored by the transport layer in this scenario. The many communication streams between these applications of students and lecturers via online segments must be kept up by the transport layer. The data will then be segmented and managed into application data streams. 

At the Transport layer, headers must be appended to each piece of application data to specify the communication with which it is associated. Each piece of data may be forwarded to the appropriate application at the receiving host. Additionally, a complete data stream that the Application layer can use must be created from these discrete pieces of data. In order to reassemble the data fragments into streams that may be transmitted to the Application layer, the Transport layer protocols explain how to use the header information. 

The Transport layer must recognise the target application in order to transmit data streams to the appropriate apps. The Transport layer identifies an application in order to achieve this. This identifier is known as a port number in TCP/IP protocols. Every software application that requires network connectivity is given a port number specific to that host. The transport layer header uses this port number to identify the application with which this particular piece of data is associated. The Transport layer serves as a conduit for network transfer between the Application layer and the lower layers. Data from various discussions is accepted by this layer, which then sends it to the lower layers in easily comprehensible chunks that can finally be multiplexed over the medium. Applications do not need to be aware of the specifics of how the network is configured. Without regard to the type of destination host, the type of medium over which the data must travel, the path the data must follow, the congestion on a connection, or the size of the network, the apps create data that is sent from one application to another. 

Additionally, the fact that numerous programmes are transferring data over the network is not known to the lower layers. Data delivery to the proper device is their responsibility. After sorting these components, the Transport layer delivers them to the proper application. There are various Transport layer protocols because different applications have different needs. In order to be properly processed by some programmes, segments must arrive in a very specific order. 

5) NETWORK LAYER

Network layer is at layer 3. The subnet's functionality is governed by the network Layer. Delivering packets from source to destination across numerous links is the primary goal of this layer (networks). A network layer is not required if two computers (systems) are connected via the same link. It serves as a network controller and sends the signal through a variety of channels to the other end. In addition, it separates incoming packets into messages for higher levels and breaks outbound messages into packets. Since the routing issue in broadcast networks is straightforward, the network layer is frequently minimal or nonexistent. The learner sends the information to the online learning system from their PC. The information that students give is really sent in packets to the IT centre for online learning. When the data is delivered to the IT centre for online learning, the packet is divided into smaller pieces. When a student wants to send data, the network must first be addressed by a computer (IP Address) before the data can reach the IT centre. The network that students use is their home network utilising a distinct LAN from the IT centre, which is using the College campus network. The source of the data is the IP address, and the data's final destination is the IT center's online learning

6) DATA LINK LAYER

Node-to-node data transfer, framing, physical addressing, flow control, access control, and error correction from the physical layer are all provided by the data link layer. The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer are two of the layers' two sub-layers. The data link layer can offer the optimal data transmission method and handle data flow control thanks to the MAC address layer. The LLC layer recognized line protocols and offers error and flow control over the physical channel.

The data link layer adds a header to the frame in physical addressing to specify the physical address of the frame's sender and receiver. According to the size of the NIC's frames, the data link layer breaks the network layer's packets into digestible data units called frames during framing (Network Interface Card). When the student's computer and the modem are connected into the same link for access control, the data link layer provides a protocol to identify which device has control over the link at any given time.

7) PHYSICAL LAYER

OSI physical layer position the lowest layer among the other layers is the model layer. Electrical or physical equipment, like fiber optic cables, network interface cards, wireless access points, modems, and routers, can convey data to other devices at the physical layer. This layer is in charge of delivering bits from source devices, also known as sending devices, across network communications media to receiver, also known as destination devices.

 According to the project scenario, five network components—NIC (1), wireless access points (1), modem (1), router (1), and switch (1) are employed in the physical layer to send data to the next destination (1). The network interface card, or NIC, controls the information exchange between the network and the user. The student's PC and wireless access point can now communicate thanks to the NIC. It indicates that the student's computer can connect to his WIFI first using a modem and then a local area network (LAN).

When a student opens an Online Learning System web page, their computer sends the request to their network card, which turns it into an electrical signal. From one node to the next node, this electrical signal will transmit the individual bits through the transmission media. The bits will be delivered to the data connection layers through this mechanism. To get the data to the router, a coaxial cable network is used. Prior to sending data to the college network server and IT Center, the router will first transfer data to a cloud via the internet. Data will be sent to the college server via a router via the internet, and the server will respond by sending the data back to the router for transmission to the IT Center. IT Center will respond by delivering the web page of the Online Learning System back to the network card as synchronization of bits that develop in electrical signal after receiving the data via router. This signal is received by the NIC card, which converts it into information that the student's PC can use to show the Online Learning System website.