What is the OSI Model
The OSI stands for Open Systems Interconnection, OSI consists of seven-layer that are used by computers to make communicate over a network. It is developed in the early 1980s and is referred to as the first standard model for network communication.
The TCP/IP model is used nowadays instead of the OSI model. Due to the feature to visualize and communicate how network operation OSI model is still used by many companies. The OSI model also helps isolate and troubleshoot problems in the network.
Characteristics of the OSI Model
The important characteristics of OSI models are
- A layer should only be used when specific levels of abstraction are required.
- Each layer’s function should be chosen according to internationally accepted norms.
- There should be a big number of layers so that various functions are not grouped together in the same layer. It should also be small enough that the architecture does not become overly convoluted.
- In the OSI model, each layer performs primitive functions by relying on the layer below it. Every layer should be able to deliver services to the layer above it.
- Modifications to one layer should not need modifications to other layers.
What is TCP/IP Model?
TCP/IP stands for Transmission Control Protocol/ Internet Protocol. It was created as a concept to provide a highly stable and end-to-end byte stream over an unreliable internet connection.
TCP/IP gives an idea about how each and every computer should be connected to the internet and how can you send and receive data between them. It also helps you to make a virtual network while connecting two or more computer networks.
Characteristics TCP/IP Model
TCP/IP protocol characteristics are
- It supports flexible architecture
- The network remains intact in TCP/IP until both the source and destination machines are operational.
- Easy to add more systems to a network
- TCP allows for flow control, ensuring that the sender never overwhelms the receiver with data.
Difference between OSI Model and TCP/IP Model
| OSI(Open System Interconnection) | TCP/IP(Transmission Control Protocol / Internet Protocol) |
|---|---|
| It has seven layers | It has only four layers |
| It is an independent standard protocol | The TCP/IP model is built on standard protocols that the Internet has grown around. |
| It acts as a communication gateway between the network and final user | A connection protocol that assigns a host network over the Internet. |
| It provides quality services. | It provides poor quality services. |
| Difficult than TCP/IP | It is simpler than OSI |
| In the OSI model, protocols are unknown. | In TCP/IP, returning protocol is not difficult. |
| The OSI header smallest size id 5 bytes | 20 bytes is the smallest size of the TCP/IP. |
| Transport Layer is Connection Oriented. | The Transport Layer can be both connection-oriented and connection-less. |
| Follows vertical approach | Follows horizontal approach. |
OSI Model Explained: The OSI 7 Layers
7. Application Layer
The application layer employs end-user applications such as web browsers, email programs. The application layer allows protocols that allow the software to transmit data and meaningful data to the users.
Ex: Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), and Domain Name System (DNS).
6. Presentation Layer
The Presentation Layer is the OSI model’s sixth layer. The Translation Layer is another name for this layer. The function of the presentation layer is to transmit the data from the application layer to the session layer. Because it is responsible for maintaining the right syntax of the data it either receives or sends to another layer, the presentation layer is also known as the Syntax layer (s). This layer clearly specifies how the data is encoded, encrypted, and compressed between the two devices and makes sure that the transmitted data is received correctly on the receiver’s end.
5. Session Layer
The session layer creates communication channels, known as sessions, between devices these layer functions are starting the session, keeping them open and functioning while transferring the data, and closing down after the data is transferred correctly. While transferring the data, the session layer always define checkpoints and the devices can resume the transmission of the data from the last checkpoint if any of the session is interrupted while transferring the data.
4. Transport Layer
In the open systems interconnection (OSI) network model, the transport layer is the fourth layer.
The OSI model breaks down the transporting data in the network to 7 small groups. Each of the seven OSI levels has a task or group of tasks allocated to it.
This layer also performs error correction, data segmentation, and desegmentation before and after the data is transferred over the network.This layer is also in charge of flow control and ensuring that segmented data is transmitted in the correct sequence across the network.
Layer 4 (the transport layer) performs its functions using the transmission control protocol (TCP) and the user data protocol (UDP).
3. Network Layer
The network layer serves two primary purposes. One method is to divide segments into network packets and then reassemble the packets on the receiving end. The other method is to route packets by determining the best path across a physical network.
2. Data Link Layer
The data link layer is the second layer of the OSI layered model. This layer is one of the most complex layers and has complex functions and responsibilities. This layer hides the underlying hardware details and is referred to as a communication to the upper layers.
The data link layer works between two hosts that are somehow directly connected. This direct connection can be a point-to-point connection or a broadcast. The systems in the broadcast network must be on the same connection. Datalink layer work tends to be more complex when there are multiple hosts in a single collision domain.
The data link layer is responsible for converting the data stream into a bit-by-bit signal and transmitting it over the underlying hardware. The receiver end of the data link layer receives the data in the form of an electric signal from the hardware and transfers it into the next layer after converting it into the recognizable frame format.
The data link layer has two sublayers.
- Logical link control: Handles protocol, flow control, and error control
- Media access control: Handles actual control of media
1. Physical Layer
The physical layer is in charge of the physical cable or wireless link between network nodes. It describes various connection techniques such as electrical cable, wireless that connect various devices. The main role of the physical layer is to take the control of raw data transferring, which is simply a series of 0s and 1s, as well as bit rate control
Advantages and Disadvantages of OSI model
Advantages of OSI models are
- It is a generic model that may be used to guide the development of any network model.
- It is a multi-tiered model. If the interfaces between the layers do not change drastically, changes to one layer have little influence on the others.
- It distinguishes clearly between services, interfaces, and protocols. As a result, it is versatile. Each layer’s protocols can be simply adjusted depending on the nature of the network.
- Both connection-oriented and connectionless services are supported.
Disadvantages of OSI models are
- It is purely a theoretical model & This restricts its practical implementation.
- The OSI model is very complex.
- It is very slow as well as costly
- When practically deploying, the session layer and presentation layer have very few functions
Advantages and Disadvantages of TCP/IP model
Advantages of TCP/IP models are
- It can deploy in practical condition
- It allows cross-communication among heterogeneous networks
- It is callable, client-server architecture
Disadvantages of TCP/IP models are
- Not generic in nature
- It does not distinguish between the ideas of services, interfaces, and protocols. As a result, it is unsuitable for describing new technologies in new networks.
- Difficult to set up and maintain compared to NetBEUI or IPX/SPX