7 Layers of the OSI Model

As we all aware for computer networks, we need laptop, LANs, Router, switch, Internet, and routing protocols, but how all these parameters are interconnected with each other? We always heard that Switch works at Layer-2 and Router works on Layer-3, but what all these layers? In this Blog, we will discuss and understand the 7 Layers of the OSI Model.

7 Layers of the OSI Model

OSI stands for Open System Interconnection. OSI Model contains 7 Layers that computer networks use to communicate with other devices over a network.

There are seven layers in the OSI model that define the process and play their role in traveling the traffic from one device to another

Read more on How Networks Works: https://techblog.kbrosistechnologies.com/what-is-network-basics/

7 layer of OSI Model Diagram

7 Layers of the OSI Model : Explained

Let’s understand the OSI model in detail that how it works and why it is important in Computer networks.

7. The Application

• It is part of the Upper Layer in the OSI Model
• The interface between the user application and the Network has been enables as this layer.
• Web browsers and email clients such application or software are applicable here.
• Examples are the Hypertext Transport Protocol (HTTP), File Transfer Protocol (FTP), Post Office Protocol (POP), Simple Mail Transfer Protocol (SMTP), and Domain Name System (DNS).

6. The Presentation

• It is part of the Upper Layer in the OSI Model
• Data is prepared for the Application layer.
• Compression, Encapsulation, and De-Encapsulation between two devices.
• Control the Formatting and Extensions to make ensure that data is present to the user in proper format like Doc, test, Image, video etc.
• Protocols used are GIF, JEPG, Doc, MP4, ASCII etc.

5. The Session

• It is part of the Upper Layer in the OSI Model
• Communication channels or Sessions between devices has been created.
• This layer can helps to attempt to recover the session, if a session is broken or session expired.
• Session communication could be one of three categories:
  • Full-Duplex – simultaneous two-way communication
  • Half-Duplex – two-way communication, but not simultaneous
  • Simplex – one-way communication
• TCP/IP is not responsible for Sessions.

4. The Transport

• The Transport layer is part of the Lower Layer.
• It is not just sending or transporting the data, its main function is to ensure that traffic is delivered reliably, error-free, and acknowledged.
• Transport layer communication falls under two categories:
  • Connection-oriented – requires that a connection is reliable, agreed and will be must ack by both ends. It does Windowing, Sequencing, and segmentation in smaller pieces for transport. Also, it Acknowledged the data delivery, otherwise, data is retransmitted till delivery.
  • Connectionless – requires no connection and reliability.
• Two Transport layer protocols under the TCP/IP protocol
  • Transmission Control Protocol (TCP) – connection-oriented.
  • User Datagram Protocol (UDP) – connectionless

        3. The Network

• It is Lower Layer
• On the Network Layer, internetwork communication will be performed.
• Layer-3 devices or routers performed inter-communication.
• These layer-3 Devices work as Gateways to send and receive traffic
• Routing protocols such as RIP, EIGRP, OSPF, IS-IS, and BGP are used at this layer to identify the best and shortest path.
• Provide IP addressing as Logical Addressing in the network to identify the devices in the network
• IPv4 and IPv6 are used broadly on this layer.

      2. The Data Link

• This is also part of the Lower Layer.
• The data-link layer is responsible for switching or intra-Vlan or Intra network communication.
• The Data-Link layer consists of two sublayers:
  • Logical Link Control (LLC)
  • Media Access Control (MAC)
• Local Area networking happens at this layer.
• VLAN, trunk, ISL, and 802.1q protocols are used at this Layer.
• It works on a Mac address instead of an IP Address.
• At this layer inter-network communication is not possible.
• Layer-2 Devices or Switches and hubs are used at this layer for Switching.

1. The Physical

• The physical layer is responsible for the physical cable or wireless connection between network nodes.
• It uses a connector, cable, or wireless signals to connect the devices.
• It is responsible for transmission of the raw data, which is simply a series of 0s and 1s.
• This is the most important layer as Devices should be physically up, and running and ready to communicate in the network.

OSI Model vs TCP/IP Model

Conclusion

The 7 Layers of the OSI model serves as a reference framework, enabling different communication protocols and technologies to interoperate by standardizing the functions of each layer. Each layer in 7 Layers in OSI Model performs specific tasks, and data travels down through the layers of the sender and up through the layers of the receiver, encapsulating and decapsulating information at each level.  All 7 Layers of the OSI Model open standard for all vendors, OEM, users globally. It defines a set of rules, process and practice that how data will travel and process till user.

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