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7 OSI Model Layers Explained with Functions and Architecture

Heena Rajpal/45138/5
Computer NetworkCSE Subject

What is the OSI model? What are the OSI layers and their functions?

These are the common questions about OSI model architecture.

Table of Contents:

  • What is OSI Model?
  • Functions of Each OSI Layers
    • Physical Layer
    • Datalink Layer
    • Network Layer
    • Transport Layer
    • Session Layer
    • Presentation Layer
    • Application Layer

What is OSI Model?

The International Standards Organisation (ISO) has proposed a reference model that covers all the aspects of network communication across all types of computer systems. This model is called the Open System Interconnect (OSI) model.

What are the different layers in the OSI model?

The OSI Model is a layered architecture consisting of seven layers. In this article, I will explain 7 layers of the OSI model in networking with a layered architecture.

Sr. No. OSI Layer
Layer 7 Application Layer
Layer 6 Presentation Layer
Layer 5 Session Layer
Layer 4 Transport Layer
Layer 3 Network Layer
Layer 2 Datalink Layer
Layer 1 Physical Layer

The standard model is necessary to ensure that worldwide data communication systems are developed in a way that they are compatible with each other.

Beginners, here is a trick for you to remember all 7 layers of the OSI model in networking. You can memorize it in the right order using the mnemonic:

Please Do Not Throw Sausage Pizza Away

7 Layers of OSI Model in Networking Explained with Layered Architecture

It’s easy!

If you are preparing for placement, many of the networking companies ask questions on OSI layer architecture.

You can check the interview experience shared by some of the networking companies.

  • Riverbed Interview Questions
  • Juniper Networks Interview Questions
  • Cisco Interview Questions

Let’s check these OSI layers in detail.

7 OSI Layers and Their Functions in Networking

The functionalities of these layers are as follows:

1. Physical Layer

It maintains the physical connection and defines the voltages and data rates. Everything related to signals is handled here including the transmission of digital bits as electronic signals. It decides if the transmission mode will be simplex, half-duplex or full-duplex. It defines the topology configuration, synchronization, and various such issues.

2. Data Link Layer

The data here is in the form of frames. It performs synchronization, error detection, and correction, and assembling messages into frames. Here is also the responsibility of receiving acknowledgments for messages and taking further steps accordingly. Hence it ensures reliable transmission of each message.

3. Network Layer

The data here is in the form of packets. It manages the routing of data. This layer takes decisions for routing and acts as a network controller. It divides the outgoing messages into packets and assembles the incoming packets into messages.

Internet Protocol is also equipped with a Network layer. There are two IP address versions as IPv4 and IPv6. Do read the difference between IPv4 and IPv6 IP address to know in particular.

4. Transport Layer

It decides if the transmission is to take place in parallel or a single path. It takes care of multiplexing and guarantees transmission of data from one end to the other.

Tansport layer also breaks the data into smaller groups hence performing splitting and segmentation.

TCP and UDP are the two most useful protocol that works on the transport layer.

Application Oriented OSI Model Layers:

Following are the application-oriented OSI model layers. It deals with actual application data and its related activities such as encoding-decoding, data representation, session management. Let’s dig into it.

5. Session Layer

It manages and synchronizes conversations between two different applications by establishing a session and ending a session. It includes logging in and out of the users with user authentication details and auditing for the purpose of billing as well.

6. Presentation Layer

This, as the name suggests, works on how the data is presented to the users. It ensures that the receiver system can read the data sent by the sender. This is done by translation of the file format into a universal code or into the code apt for the receiver machine.

7. Application Layer

This is the top-most layer in 7 layers of the OSI model in networking. It directly interacts with the user. The login and password check takes place here. Re-transmission of files due to any errors, manipulation of information, etc. takes place here. It deals with user interface design.

Finally…

I have touched different OSI layers and their functions.

Further reading: This OSI model layered architecture has its own pros and cons. To understand it, read 12 Advantages and Disadvantages of OSI model Layered Architecture.

Hope this is helpful to get a clear understanding of OSI layers and their functions. You can use the comment section if you come across any doubt while understanding these 7 layers of the OSI model in networking.

Computer NetworkOSI model
Heena Rajpal
Heena Rajpal is pursuing Computer Science Engineering from Indore. She has a knack for writing and an inquisitive outlook towards Computer Science fields like Database Management Systems, Object Oriented Programming and languages like C, C++, JAVA, Python, HTML etc.

Your name can also be listed here. Got a tip? Submit it here to become an CSEstack author.

Comments

  • Reply
    Randy Borman
    October 5, 2017 at 10:33 pm

    Hey Heena, You have performed an excellent write up by writing this post in detail. From my side, I will suggest to my college friends. I’m sure they’ll be benefited from this detailed article about networking.

    Thanks!

  • Reply
    Vikram Raj
    June 29, 2020 at 6:19 am

    Excellent work!!! Keep it up

    • Reply
      Aniruddha Chaudhari
      June 30, 2020 at 9:23 am

      Thanks, Vikram! I hope you enjoy reading other articles as well.

  • Reply
    Rehan
    November 2, 2020 at 4:46 pm

    Simple and very informative.

    • Reply
      Aniruddha Chaudhari
      November 3, 2020 at 8:47 am

      Thanks, Rehan!

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Computer Network

CN- How does Comp Network Work?

CN- Importance of Network Topology

CN- OSI Layer Architecture

CN- Pros and Cons of OSI Model

CN- Physical vs Logical Topology

CN- Conn-Oriented Vs Conn-less

CN- Ethernet in Detail

CN- TCP vs UDP Protocol

CN- Different Classes of IPv4 Address

CN- IPv4 Vs IPv6 Address

CN- Subnetting Vs Suppernetting

CN- Internet Traffic Shaping Algo

Online Tool

CN- IP Subnet Calculator 

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