What is OSI Model? 7 Layers Explained with Functions | Full Form of OSI

OSI stands for (Open Systems Interconnection) model is a conceptual technique that is going to describe about how the networking system make communication and send data from a sender to recipient. Therefore, now we will guide you about what is OSI model and 7 layers explained with functions; as well as full form of OSI model with ease. Make ensure that at the end of this article, you will get fully educated about what is OSI Model without any hassle.

OSI Model Definition

OSI Reference Model was introduced by International Organization for Standardization (ISO) in 1984. OSI stands forOpen System Interconnection” is a conceptual model that describes how to flow all information from one software application in is presented in computer system transfers through physical resources to software application in other computer system.

OSI model likes as universal language in computer networking system, and it is totally depend on their abstract layers such as (Physical, Data Link, Network, Transport, Session, Presentation, and Application).

Every layer is allotted for specific task, and every layer is self contained, so that each layer in OSI model is capable to perform their functions independently. Internet modem is not depending on the OSI conceptual model, but it helps to troubleshoot all network issues.

OSI Model Tutorial Headlines:

In this section, we will show you all headlines about this entire article; you can check them as your choice; below shown all:

  1. OSI Model Definition
  2. Types of Network Layers of OSI Model
  3. What is Importance of OSI Model?
  • Physical Layer (Layer 1)
  • Data Link Layer (Layer 2)
  • Network Layer (Layer 3)
  • Transport Layer (Layer 4)
  • Session Layer (Layer 5)
  • Presentation Layer (Layer 6)
  • Application Layer (Layer 7)
  1. Advantages of OSI Model
  2. Disadvantages of OSI Model
  3. FAQs (Frequently Asked Questions)
  • What is the 7 layers of the OSI model with example?
  • Why is it called OSI model?
  • Why does the OSI model have 7 layers?
  • What are the functions of the OSI layers with diagram?
  • Where is OSI model used?
  • Why is OSI important?

Let’s Get Started!!

What is Importance of OSI Model?

The importance of the OSI model can be summarized as follows:

Shared Understanding of Complex Systems: Engineers can use the OSI model to organize and model complex networked system architectures, separating the operating layer of each system component according to its main functionality.

Handles Networking Vulnerabilities and Security issues: The OSI model facilitates the breakdown of the communication system into seven layers that are allowing the isolation of networking issues at their origin. This enables the addressing of networking vulnerabilities and security issues without disturbing the entire OSI framework.

Troubleshooting Network Devices: The OSI model is crucial for designing, manufacturing, and troubleshooting network technology. When a networking unit fails or an application goes down, the OSI model allows administrators to zero in on the specific OSI layer and identify the issue.

Guidance for Technology Vendors and Developers: The OSI model guides technology vendors and developers in creating digital communication products and software programs that can interact with other devices on a network.

Types of Network Layers of OSI Model

Here, we will explain working structure of 7 network layers of IOS Model with their functions; below describe each one:

How Does OSI Model Work?

osi model

Diagram of OSI Model

Physical Layer (Layer 1)

Physical layer has last position in the OSI reference model. The main role of physical layer is to make physical connection in between all devices which are linked with over the computer network, and it has ability to contain all data into bits form. It is other main responsibility is to transmission every bit from one connected node to another and so on. This layer will receive data and converted it into bits form such as 0 or 1 form, and finally it moves them toward Data Link Layer.

Physical layer refers to physical resources like as network hubs, cabling, repeaters, modem, and more.

Read More – Physical Layer Functions with their Devices

Data Link Layer (Layer 2)

The data link layer likes as network layer, and it helps to transfer data in between multiple network devices over sane network. This layer grabs all packets from network layer and splits them into small parts, and these small parts known as “Frames”. Data link layer has responsibility to flow control and error control over intra-network communication. When packet reaches in a network, then major role of DDL layer is to send it to Host point with the help of MAC address.

Data Link Layer (DDL) has two variants like as:

  • Logical Link Control (LLC): Logical Link Control helps to deliver identifies the line protocols as well as error free data flow control.
  • Media Access Control (MAC): Media Access Control helps to deliver multiplexing and flow control for all devices transmission over the network.

Network Layer (Layer 3)

Network layer helps to transmit data from one host to another host that is placed over different networks. This layer implements multiple packet routing system for identifying best physical route for data to arrive appropriate destination point like as choose of shortest path for making transmission of all packets, from number of routes are available. Network’s header contains all sender & receiver’s IP addresses.

Transport Layer (Layer 4)

Transport layer is also known as “Heart of OSI”. Transfer layer provides the best point to point communication in among of two nodes. It grabs all data from session layer side and splitting it into multiple parts, is known as “Segments” before moving them toward network layer. This layer is used on the all receiving network devices, which are getting to responsible to reassemble all segments into data form, and this data is consumed by session layer.

Main objective of transport layer is to flow control and error free control. Its flow control monitors maximum speed of data transmission that sender host is getting fastest connection, and it does not degrade receiver along with slow connection.

Transport layer uses two protocols like as:

Transmission Control Protocol: This protocol allows to entire system to make communication over the internet, and it helps to build and maintains connection in between all hosts.

User Datagram Protocol: This is untruth able transport layer because in this scenario receiver is not able to move an acknowledgement, when packet is arrived.

Note: Operating system helps to operate the transport layer, so it is integrated part of O/S, and it makes communication along with Application layer by firing system calls.

Session Layer (Layer 5)

Session layer helps to generate several communication channels in between multiple devices, they known as “Session”. This layer has responsibility to open sessions when data is getting to transfer, and finally shut down when communication ends. Session layer is able to set checkpoint while moving data, if session is got hindrance then network device has right to resume data send from last checkpoint.

Presentation Layer (Layer 6)

Presentation Layer is also known as “Translation Layer or Syntax Layer”. This layer helps to translate all data for next layer “Application Layer” depend on syntax or semantics which are accepted by application layer. Presentation layer is capable to manage encryption and decryption as per need of application.

If, two network devices want to make communication over encrypted connection then this layer has responsibility to append  encryption on the sender side while decoding the encryption on the receiver side which is capable  to present the application layer along with unencrypted and readable data.

Application Layer (Layer 7)

Application Layer is toppest layer of OSI Reference Model. This layer allows all users to make directly interaction with data for example software application such as web browser and email clients implement on the application layer to establish communication. This layer determines communication partners, resource availability, and synchronizes communication.

Application layer protocols enable with HTTP as well as SMTP.

What are Advantages and Disadvantages of OSI Model?

There are various remarkable pros and cons of OSI network model; below shown each one:

Advantages of OSI Model

Here are some common advantages of the OSI model, including:

Modularity and Layered Architecture: The OSI model is divided into seven layers, each with a specific set of functions. This layered approach lets you easy to understand, troubleshooting, and modification of different context of a network without getting to affect the other layers.

Interoperability: The clear division of responsibilities among layers promotes interoperability between different vendors and systems. As long as each layer adheres to the specified interfaces, components from different manufacturers can work together seamlessly.

Facilitates Protocol Development: Each layer in the OSI model can be associated with a specific protocol or set of protocols. This modular design helps to simplify the development of new protocols otherwise the enhancement of existing ones without getting to affect the whole system.

Eases Troubleshooting: The layered structure simplifies the troubleshooting process. These issues can be resolved to a certain layer that making it easier to identify and rectify problems; then reduces the overall complexity of network maintenance.

Clear Communication Standards: The OSI model provides a common language and conceptual framework for communication systems. This standardization is getting to help in the establishment of communication protocols that makes the ensure consistency across diversified networking technologies.

Scalability: The modular design of the OSI model makes it scalable. New technologies and functionalities can be added by introducing new layers or modifying existing ones without affecting the entire network architecture.

Promotes Vendor Independence: The OSI model encourages the development of protocols and technologies that are not tied to a specific vendor.

Global Standardization: The OSI model provides a globally recognized standard for network architecture. This standardization helps to make communication and collaboration over the global scale.

Guides Product Development: Network equipment and software developers use the OSI model as a reference to guide their product development. This is making ensure that products are well designed with compatibility and interoperability.

Disadvantages of OSI Model

While the OSI (Open Systems Interconnection) model offers numerous advantages; it’s important to acknowledge some of the potential disadvantages or criticisms associated with it:

Complexity: The OSI model, with its seven layers, can be perceived as overly complex, especially for those new to networking. This complexity may lead to difficulties in understanding, implementing, and troubleshooting network issues.

Not Always Reflective of Real-World Protocols: The OSI model is a conceptual framework, and in practice, real-world networking protocols such as TCP/IP are often more integrated and less neatly separated into distinct layers. This can make direct mapping between the OSI model and actual networking implementations challenging.

Lack of Timely Adoption: The OSI model faced challenges in terms of adoption. By the time it was fully developed, the TCP/IP model had already gained widespread acceptance and became the dominant networking architecture. As a result, the OSI model is often considered more of an academic or theoretical framework.

Rigid Layer Boundaries: The strict layer boundaries of the OSI model may not always align with the actual behavior of some network protocols. In practical implementations, certain functionalities might span multiple layers, and the rigid layering of the OSI model doesn’t always reflect this reality.

Resource Intensive: Implementing all seven layers of the OSI model can be resource-intensive in terms of both hardware and software. In some cases, the additional overhead introduced by adhering strictly to the OSI model may not be justified in terms of performance.

Focus on Presentation and Session Layers: The presentation and session layers of the OSI model, responsible for data formatting and establishing, maintaining, and terminating sessions, respectively, have seen limited practical use. Many application-layer functions are often handled by the application layer itself or by protocols like HTTP and FTP.

Limited Adoption in Industry: The TCP/IP model, which has fewer layers and aligns more closely with the protocols used on the internet, is the dominant model in the networking industry. As a result, the OSI model is sometimes viewed as less relevant in real-world network design and troubleshooting scenarios.

Overlapping Functionality: Some critics argue that there is overlapping functionality between layers, especially in the lower layers (physical, data link, and network). This can lead to inefficiencies in protocol design and implementation.

Difficulties in Standardization: While the OSI model provides a framework for standardization, achieving global consensus on specific protocols and standards across all layers has proven challenging. The networking industry often relies on de facto standards, with practical implementations influencing the development of protocols more than theoretical models.

TCP/IP Dominance: The dominance of the TCP/IP model in real-world networking has led to a situation where many professionals are more familiar with it than the OSI model. This makes it more challenging to promote and implement the OSI model in practical network environments.

FAQs (Frequently Asked Questions)

What is the 7 layers of the OSI model with example?

The OSI model is a conceptual technique that is going to use for exploring the functions of a networking system. It consists the seven layers like as Physical, data link, network, transport, session, presentation layer and application layer. Examples for Physical layer are Ethernet cable and Serial Cable.

Why is it called OSI model?

The OSI (Open Systems Interconnection) model is the conceptual framework that is designed by the International Organization for Standardization, which allows to make diverse communication system to communicate with using of standard protocols.

Why does the OSI model have 7 layers?

The main concept of OSI is the process of making communication in between two endpoints in a network that can be spitted into seven different group of related functions or layer. Every user or program is on the device that can offer those 7 layers of function.

What are the functions of the OSI layers with diagram?

The OSI model assists the uses and operator of computer networks to identify the needed hardware and software to establish their computer network. As well as getting to understand and communicate the process the followed by the components making communication across the networking.

Where is OSI model used?

Mostly, IT networking professionals are going to use the OSI model or conceptualize; how data is sent or obtained over the network.

Why is OSI important?

The OSI lets you to determine the threats across your entire tech stack, as well as OSI model is also used for decades to assist IT professionals networking and troubleshoot issues.

Final Verdict

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Read More – Application Layer in OSI Model: Functions, Protocols, Examples, & Services!!

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