Overview of OSI model And TCP/IP model

OSI Model is a hypothetical networking framework that uses specific protocols and mechanisms in every layer of it. This model is used to divide the network architecture into seven different layers conceptually

OSI Model

• OSI stands for Open System Interconnection is a reference model that describes how information from a software application in one computer moves through a physical medium to the software application in another computer.
• OSI consists of seven layers, and each layer performs a particular network function.

Seven layers of OSI model

1. Physical layer
2. Data-link layer
3. Network layer
4. Transport layer
5. Session Layer
6. Presentation Layer
7. Application Layer

TCP/IP Model

• The TCP/IP model is not exactly similar to the OSI model.
• The main work of TCP/IP is to transfer the data of a computer from one device to another.
• The main condition of this process is to make data reliable and accurate so that the receiver will receive the same information which is sent by the sender.
• To ensure that, each message reaches its final destination accurately, the TCP/IP model divides its data into packets and combines them at the other end, which helps in maintaining the accuracy of the data while transferring from one end to another end.

How Does the TCP/IP Model Work?

Whenever we want to send something over the internet using the TCP/IP Model, the TCP/IP Model divides the data into packets at the sender’s end and the same packets have to be recombined at the receiver’s end to form the same data, and this thing happens to maintain the accuracy of the data. TCP/IP model divides the data into a 4-layer procedure, where the data first go into this layer in one order and again in reverse order to get organized in the same way at the receiver’s end.

Five layers of TCP/IP model

1. Network Interface layer
2. Network Access layer
3. Transport layer
4. Application layer

Functionality Of Each Layer

Physical Layer

1. This is also the layer where the data gets converted into a bit stream, which is a string of 1s and 0s.
2. The physical layer of both devices must also agree on a signal convention so that the 1s can be distinguished from the 0s on both devices.
3. It establishes, maintains and deactivates the physical connection.

Data-link Layer

1. When, you connect your wi-fi network or LAN cable. then, the data-link layer is help you to connect with network.
2. Its help your devices to communicate in proper way to share data or information to each other without any causing to frames.
3. Framing: The data link layer translates the physical's raw bit stream into packets known as Frames. The Data link layer adds the header and trailer to the frame. The header which is added to the frame contains the hardware destination and source address.
4. Flow control: It ensure that, the data transmission on both side will be same. If sender's data rate of transmission is more than the data rate of receiver, the data or packet will be drop or corrupted.
5. Error control: This functionality achieved by adding calculated value CRC (Cyclic Redundancy Check) that is placed to the Data link layer's trailer which is added to the message frame before it is sent to the physical layer. If any error occurs at the receiver side then it send acknowledgement message to sender to resend the corrupted frames.

Network Layer

1. Network layer is like your GPS.
2. Its help to the data to determine the best path for data transmission and frame travel including traffic and other factor.
3. Its working is routing and addressing.
4. Internetworking: An internetworking is the main responsibility of the network layer. It provides a logical connection between different devices.
5. Addressing: A Network layer adds the source and destination address to the header of the frame. Addressing is used to identify the device on the internet.
6. Routing: Routing is the major component of the network layer, and it determines the best optimal path out of the multiple paths from source to the destination.
7. Packetizing: A Network Layer receives the packets from the upper layer and converts them into packets. This process is known as Packetizing. It is achieved by internet protocol (IP).
8. Example: When, you open a browser for accessing the data. Then, network layer decide the best path for data transmission from web server to your devices.

Transport Layer

1. The transport layer is responsible for delivery of messages from one process to another.
2. Manage the transmission of data across a network.
3. It handles delivering of messages from one device to another. It ensure the data is sent accurately, without any pieces missing or jumped up.
4. When, we want to send the data it break the data into small chunks and send all this chunks to next layer.
5. At the receiver end, reassemble the chunks original size and sequence.

Session Layer

1. Its responsible for managing, setup and closes the communication session between devices. A session like a phone call or meeting its a period during which devices communicate.
2. Dialog control: Session layer acts as a dialog controller that creates a dialog between two processes or we can say that it allows the communication between two processes which can be either half-duplex or full-duplex.
3. Synchronization: Session layer adds some checkpoints when transmitting the data in a sequence. If some error occurs in the middle of the transmission of data, then the transmission will take place again from the checkpoint. This process is known as Synchronization and recovery.

Presentation Layer

1. Presentation layer leads with how data looks and is presented.
2. Its responsible for formatting, encryption and compressing data to ensure its sent and readable and secure format manner.
3. Encryption: When, you send a password or credit card information over a secure website, the presentation layer encrypts the data, so its secure during transmission.
4. Formatting: It ensure that, the text, images and another format data is well structured. Because, the different devices or applications will be interpreted that data into proper way.
5. Compression: Data compression is a process of compressing the data, i.e., it reduces the number of bits to be transmitted. Data compression is very important in multimedia such as text, audio, video.

Application Layer

1. Its ensure that, How your applications that communicate with the network.
2. Its help the application like Browsers, to communicate with different devices and services over the internet or local network.
3. File transfer, access, and management (FTAM): An application layer allows a user to access the files in a remote computer, to retrieve the files from a computer and to manage the files in a remote computer.
4. Mail services: An application layer provides the facility for email forwarding and storage.
5. Directory services: An application provides the distributed database sources and is used to provide that global information about various objects.

Similarities between OSI Model and TCP/IP Model?

OSI and TCP/IP both are logical models. One of the main similarities between the OSI and TCP/IP models is that they both describe how information is transmitted between two devices across a network. Both models define a set of layers. Each layer performs a specific set of functions to enable the transmission of data.

Another similarity between the two models is that they both use the concept of encapsulation, in which data is packaged into a series of headers and trailers that contain information about the data being transmitted and how it should be handled by the network.

Difference between TCP/IP and OSI Model