OSI LAYER MODEL

OSI Layer Model

What is OSI model?

The OSI model is a layered framework for the design of network systems which established in 1947 by the The International Standards Organization(ISO) that allows communication between all types of computer systems. An ISO that standard covers all aspect of network communications is the Open Systems Interconnection(OSI) model. It consists of seven separate but related layers, each of which defines a part of the process of moving information across a network.

 

Explanation on how the data travels from the Studnet's computer to reach the OnlineLearning System server which is in the Cobham College IT Center by using OSI model.

Student’s computer	Cobham College IT center
Layer 7: Application Layer The OSI model's topmost layer is the Application layer. This is the sole layer that interacts directly with user data. With the use of protocols, the application layer delivers services for network applications.   Network component: Endpoint(Computer, tablet,smartphone,etc),NIC,Operating system Packet Data Unit(PDU): Data
Student use the Hypertext Transfer Protocol (HTTP) that provided in the website of the Online Learning System server to travel data to the sever.	The server use the HTTP   to receive the data from the student’s computer.
In this layer, the data was in raw data either was received or send, this layer responsible providing services to the user.
Layer 6: Presentation Layer The Presentation layer is the OSI model's sixth layer. In the network, it mostly provides data translation, encryption and decryption, and compression.   Network component: Endpoint(Computer, tablet,smartphone,etc),Operating system Packet Data Unit(PDU): Data
In this layer, it receives the data from the application layer and performs data encryption and compression to it.	In this layer, it receives the data from the transport layer and performs data translation, decryption, and decompresses data.
The information of the email was transformed and presented into common computer language which is in binary format. The data was compress and to reduces the number of bits contained in the information while the data encrypt/decrypt was to ensure a privary/security.
Layer 5: Session layer The OSI model's fifth layer is the Session layer. It primarily aids in the setting up, termination, and management of network connections. Network component: Endpoint(Computer, tablet,smartphone,etc),Operating system Packet Data Unit(PDU): Data
In this layer, a session is created when two devices get connected for sending the data.	In this layer, the session is terminated as soon the connection is no longer required as the data is complete transfer and received.
The session layer is responsible for maintains, establishes and synchronizes the interaction between communicating systems. Generally, the sender and receiver devices will create session between of them.
Layer 4: Transport Layer The Transport layer is the OSI model's fourth layer. It is primarily in charge of data delivery from one process to the next. It controls the data flow and errors to ensure effective transmission.   Network component: Operating system Packet Data Unit(PDU): Segment
In this layer, the transport layer receives the data from the upper layer and performs segmentation. The source and destination port numbers are also included in the header file of the data before forwarding it to the network layer.	In this layer, the transport layer performs the reassembly and sequencing of data. It reads the port number of the data from the header file, and then direct it towards the Layer 6.
In this form the data will be segmented or reassembly. The segment header will  contain port number(software address such as gmail, whatsapp number and etc) and the data was in raw form.
Layer 3: Network Layer The Network layer is the OSI model's third layer. It mostly handles data transmission from one computer to another across several networks..   Network component: Routers Packet Data Unit(PDU): Packet
The network layer breaks the data segments received from the upper layer into smaller units, called data packets.	The network layer reassembles the data packets into segments for the upper layer
The segment will be put in a packet. There will be packet header and data. Packet header contain ip address of sender and receive. The data in the packet was in segment form.
Layer 2: Data-Link Layer The Data-Link Layer is the second layer of the OSI model. It performs the physical addressing of data.   Network component: Network Interface Card(NIC),Switch & Bridge Packet Data Unit(PDU): Frame
In this layer, it receives the data in the form of packets from the network layer and converts it into smaller forms, called the data frame.	In this layer, it converts the data frame into packets for the network layer.
The packet will be put in a frame. There will be frame header and data in packet form as well. The frame header contain mac address/physical address of sender and receive(switch).
Layer 1: Physical Layer The Physical Layer is the lowest layer of the OSI model and it deals with data in the form of bits or signals.   Network component: Hub,Repeater,Modem,Cables Packet Data Unit(PDU): Bits
The physical layer will get the data from the upper layer and convert it into bitstreams (0's and 1's) and send it through a physical channel.	The physical layer will convert the bitstreams into frames to be passed to the data-link layer.
The frame will through physical layer depend on wireless or cable. The data will go to switch and the mac receiver change to mac router of the receiver.