Computer network models explanation

Computer Network Models Explanation

The entire communication process takes place in different layers, where each layer performs one or more specific functions.

In data communication, two or more users can transfer data from one to another. Transferring data requires a systematic approach.

Users can communicate and transmit data using this method in an effective and organized way. It is implemented using models in computer networks and is known as the computer network model.

Computer network models are in charge of, respectively, establishing communication between sender and receiver and seamless data transport.

There are two different types of computer networks, namely the two models on which the entire data transmission process is based are the OSI Model and the TCP/IP Model.

types of computer network models

OSI Model Layers Explanation

  • World Wide Agreement or multinational body
  • The ISO is in charge of developing and marketing commercial and industrial standards that apply to all users or globally.
  • OSI= Open System interconnection
  • Without modifying the underlying Software & Hardware, allow for open communication between various systems.
  • Open System Interconnection (OSI) model= is not a protocol

The OSI model is called “open source” because of its ability to “fit anywhere”. Any connection can be established using the OSI model as long as no protocol is used because the OSI model does not support protocol establishment.

It functions without using protocols. Through the OSI model, any networking hardware that supports communication can be linked together to exchange data.

Besides the OSI model, another computer network model that is widely used is the TCP/IP model.

The OSI model, which has a layered architecture, allows for simpler data communication because each layer has a predefined structure and functions. Functionality is different for each layer and thus when combined together forms the OSI model. The general-purpose OSI model has a total of seven layers.

How to Memorize All Layers of OSI model

In this tutorial, we’ll teach you a trick that will help you remember the OSI layer model forever since once the human brain accepts anything, it uses it as an example of how something should be done.

These statements will aid in helping you remember the layers of the OSI Layer model for a very long time if you want to preserve your OSI Layer model in your brain.

We are presenting you with both examples in case you want to learn them in Hindi, Urdu, or English.

In English Example No (1)

OSI Model Mnemonics: Trick to remember the forward Layers:

“Please do not touch Steve’s Pet Alligator”

OSI Model Mnemonics

In English Example No (1)

OSI Model Mnemonics: Trick to remember the backward Layers:

“A Penguin Said that Nobody Drinks Pepsi”

OSI Model Mnemonics

Example In Hindi or Urdu:

OSI Model Mnemonics: Trick to Remember the backward Layers

 “Aj pher se test ni dena pry ga”

How do you remember the 7 layers?

What Happen when a message Travels Computer A To Computer B?

What Happen When a message Travels Computer-A to Computer-B

Organization of OSI model Layers

  • Upper Layers=L5+L6+L7 (Implemented in Software).
  • Lower Layers=L1+L2+L3( Combination of Software & Hardware).
  • Independent Network Layers= Physical is mostly Hardware.
Organization of OSI Model Layers


Application Layer:- type of communication

  • Email,
  • client/customer, Server,
  • File Transfer/Exchange

Presentation Layer: – Data conversion for encryption

  • BCD to binary

Session Layer:-

  • Start the Session
  • Stop the Session
  • Maintain order

Transport Layer:

  • Ensure that the complete file or message is delivered.

Network Layer:-

  • Routes data to different
  • The network address is the foundation for LAN and WAN.

Data Link MAC Layer:

  • Send packets based on the station address from node to node.

Physical Layer:-

  • cable or electrical signal

Responsibility of Physical Layer= transfer of bits – the sequence 1’s and 0’s that make up all computer code.

This layer serves as a representation of the physical medium that is carrying the traffic between two nodes. Your Ethernet cable or serial cables are two examples.

The data rate (bits per second) is also determined by the physical layer.

The bits must be encoded into the signal, which can be electrical or optical, in order to be conveyed.

“Layer 1 is, to put it simply, what holds the ones and zeros between two nodes”.

Data Link Layers

  • The responsibility of DL is Node to Node.
  • It makes the physical layer look error-free to the upper level
  • The data link layer sends the message to the server associated with the sender. If you’re chatting at home with a Wi-Fi connection, the data link layer sends messages from your computer to the Wi-Fi router.
  • Frames are created from packets, which are then sent from source to destination. This layer is made up of two components: Media Access Control (MAC), which utilizes MAC addresses to connect devices and specifies permissions to transmit and receive data, and Logic Link Control (LLC), which identifies network protocols, does error checking and synchronizes frames.

Network Layer

  • Responsibility= source to destination
  • And responsible for packet delivery from end to end

The network layer has two main functions. A network is breaking up the segments in a packet and reassembles the packets at the receiving end. The second is routing packets by discovering the best path in the physical network. The network layer uses network addresses (usually Internet Protocol addresses) to route packets to the destination node.

Routers are network devices that operate at Network layer 3 of the Open System Interconnection model. A router’s main duty is to make it easier for networks to communicate with one another. Consequently, a router creates a barrier between two networks. A router is required to communicate with any device that is not directly connected to your network.

Under layer-management protocols, the following are the network layer arrays:

  • routing protocols
  • Network-layer addresses assignment.
  • multicast group management

Transport Layer

  • TL Responsible- source to the destination of the entire message
  • Transport layer – ensures that the entire message reaches the destination.

Functions of Transport Layer

Service Point Addressing

  • On a computer, several programs can run simultaneously.
  • Service point addresses or port addresses are included in TL headers.
  • Network Layer each packet correct while TL entire message to the correct on that computer.

Segmentation & Reassembly

  • The message is divided into transferable parts.
  • Each segment consists of a sequence number.

Connection Control Two Types

  • First is Connectionless.
  • Second is Connection-oriented.

Flow Control

  • The transport layer is responsible= For the Follow Control.
  • Flow Control is performed end-to-end.

Error Control

  • The Transport responsible= for the Layer is the Error Control.
  • Error Control is performed end-to -end.

Session Layer

  • session layer= creates and maintains communication channels between devices
  • Session Layer is responsible for opening sessions, making sure they are open and active throughout data transfer, and shutting them once communication is finished.
  • The session layer can also establish checkpoints during data transfer so that, in the event of a session interruption, devices can pick up where they left off.

Presentation Layer

  • The presentation layer that prepares the data for the application layer and defines how two devices should encode, encrypt and compress data so that the other side receives the data correctly.
  • The data presented at the application layer is received by the data presentation layer and then processed and delivered to the session layer.

Application layer

Web browsers and email clients are examples of end-user software that is utilized in the application layer.

By end-user software, we mean any program deliverable with a user interface for external and/or internal end users.

  • Hypertext Transfer Protocol (HTTP)
  • File Transfer Protocol (FTP)
  • Post Office Protocol (POP)
  • Simple Mail Transfer Protocol (SMTP)
  • and Domain Name Systems are some examples of application layer protocols (DNS).

5 Layers of TCP IP Model

  • The entire communication process takes place in different layers, where each layer performs one or more specific functions.
  • The Internet also uses a layered communication model, called the Transmission Control Protocol/Internet Protocol=TCP/IP model.
  • The TCP/IP protocol suite enables end-to-end connectivity between devices.

5 Layers TCP/IP Model

TCP/IP model

Real Life Examples of TCP IP Model

A post office example can be used to explain the layering concept. Let’s say you want to write a letter to your friend in Lahore when you are in Multan.

After writing the letter, you put it in an envelope, write your friend’s address on it and put it in the mailbox. Since many people can live at the same address, write your friend’s name on the envelope.

Your nearest post office takes the letter to the General Post Office in Multan which forwards it to the General Postal Office in Lahore. Finally, the letter reaches the addressee and then your friend. Then, he can read the message and write a reply. Here we relate this example to the layered network model of TCP/IP. Suppose two people are chatting using a computer network.

Real Life Example of Postal System &
Real Life Example of Layered Network

Post System Step 1:- 

You only think about writing an appropriate message in a letter and don’t bother about the names of the postal workers who will handle the envelope. Furthermore, you are not required to understand the specifics of the postal delivery system.

It only has to be placed in an envelope together with the street address.

Network Layered Step 1:-

While Chatting you are concerned only about the messages without bothering about the kind of network, i.e., wireless or wired. This is called the application layer where you type a message and send it on the network.

The address of the receiving device is provided in the form of a header before the message content.

Post System Step 2:- 

You write the sender and receiver information on the envelope and put it in the letterbox. If the address is incomplete, you may get your letter back. if everything is fine, you simply trust the postal system. The name of the specific person is mentioned who can open and read the letter.

Network Layered 2:-

The transport layer establishes a connection between a client and a server. it tries to send a message but if there is some error like your computer is disconnected from the network then it informs the application program. If the network is fine, then the application trusts the transport layer that the message will reach its destination.

At this stage, the port number is added to a message header for an indication of a specific application at the destination. A port number is used to identify the application which can accept a message.

Post System Step 3:- 

A letter is moved to another city (Lahore in this example) by road or air. Handling of letters is the same either if they are letters with photographs, Eid cards, love letters, job letters, appointment letters, Degree letters, Appreciation letters containing text, etc.   

Network Layered 3:-   

A program running on the network layer moves the data to the other network. So, a chat message is transferred to another Wi-Fi router of your friend from where it is delivered to your friend and he/she can see it on screen. A network handles all messages in the same way either if they are emails, pictures, voice messages, etc.

Post System Step 4:- 

Bikes or vans may carry your letter from the letterbox to the general post office.

Network Layered 4:-  

The data link layer sends a message to the server connected with the sender. If you are chatting at home with a Wi-Fi connection, then the data link layer sends messages from your computer to the Wi-Fi router.

Post System Step 5:- 

For your letter delivery, there is the usage of roads, train tracks and maybe airlines.

Network Layered 5:-  

The physical layer is the physical medium used in communication, like cabling, etc.

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