Lec-2: Introduction to Computer Network | OSI MODEL in easiest Way in Hindi | Need of OSI model

Summary

This video script delves into the fundamentals of computer networking, emphasizing the importance of sharing data between devices. It outlines the necessity of protocols for effective communication, ensuring that data sent by a sender is intelligibly received by the receiver. The script also touches on wired and wireless connections, the role of clients and servers, and the concept of inter-process communication within a single machine. It introduces the OSI model, explaining its seven layers and their significance in standardizing network communication, and hints at the exploration of each layer's functionalities in subsequent videos.

Takeaways

• 🌐 A computer network is a system that connects various computing devices to facilitate data sharing.
• 🔗 The primary purpose of a network is to enable communication between different types of devices, both homogeneous and heterogeneous.
• 💬 Communication involves a sender and a receiver, which can be machines or users operating machines, and requires a connection, either wired or wireless.
• 📦 Data is transmitted in packets from the sender to the receiver through the established connection.
• 🔍 To ensure the receiver can understand the data, protocols must be in place on both the sender's and receiver's machines, guiding the data transmission process.
• 🗣️ An example used to illustrate communication is a phone call between people who speak different languages, emphasizing the importance of a common protocol for understanding.
• 💻 The script differentiates between communication within a single machine (inter-process communication) and between physically separated machines, which is where computer networks come into play.
• 🌐 The functionality of a computer network is to make geographically separated client and server machines appear as if they are on the same machine, providing a seamless communication experience.
• 🛠️ The script discusses mandatory and optional functionalities in network communication, such as error control, flow control, multiplexing-demultiplexing, and encryption-decryption.
• 🔑 Error control is crucial for ensuring the integrity of the data sent, while flow control prevents network congestion by managing the amount of data being sent.
• 🔐 Encryption is an optional functionality that adds a layer of security to the data transmission, particularly important for sensitive data like financial transactions.
• 📚 The OSI model is introduced as a standardized way to organize the various functionalities of network communication into seven layers, each with its own set of responsibilities.

Q & A

What is the primary purpose of a computer network?

The primary purpose of a computer network is to enable various computing devices to share data, which involves connecting homogeneous and heterogeneous devices.

What are the two main components involved in data transmission in a computer network?

The two main components involved in data transmission in a computer network are the sender and the receiver, which can be machines or users sending data through machines.

What types of connections are required for data to be transmitted between sender and receiver in a computer network?

Data transmission in a computer network requires a connection, which can be either wired or wireless.

Why is it necessary for the receiver to understand the data sent by the sender in a computer network?

It is necessary for the receiver to understand the data sent by the sender to ensure proper communication. This requires a protocol that runs on both the sender's and receiver's machines to ensure the data is understood.

What is the role of protocols in computer network communication?

Protocols in computer network communication are like a set of instructions that the sender follows to ensure that the data sent is understood by the receiver. They help in maintaining the structure and format of the data being transmitted.

Can the sender and receiver be part of the same machine in a computer network?

Yes, the sender and receiver can be part of the same machine, such as when a user inputs data on a keyboard and it is displayed on the monitor. This is an example of inter-process communication within a single machine.

What is the difference between inter-process communication and computer network communication?

Inter-process communication occurs within the same machine, such as between processes on a single computer, and is managed by the operating system. Computer network communication involves physically separated client and server machines, which is managed by network protocols.

What is the main functionality of a computer network?

The main functionality of a computer network is to provide a seamless communication environment where physically separated client and server machines can interact as if they were part of the same machine.

What are some mandatory functionalities provided by network protocols?

Some mandatory functionalities provided by network protocols include error control to ensure the integrity of the data, flow control to manage the amount of data being sent, and multiplexing and demultiplexing to manage data from multiple processes.

What are some optional functionalities that might be used in network communication?

Optional functionalities in network communication include encryption-decryption for secure data transmission, checkpointing for resuming interrupted data transfers, and other advanced features that may not be required for all applications.

Why is the OSI model important in understanding computer networks?

The OSI model is important because it provides a standardized framework for understanding how data is transmitted and managed in a network. It divides the various functionalities into seven layers, helping to organize and clarify the complex processes involved in network communication.

Outlines

00:00

🌐 Understanding Computer Networks

The paragraph introduces the concept of computer networks as a system that allows various computing devices to share data. It explains that networks can connect homogeneous and heterogeneous devices and that their primary function is data sharing. The paragraph also discusses the roles of senders and receivers, which can be machines or users, and the necessity of a connection, whether wired or wireless, for data transmission. The importance of protocols for ensuring that data sent is understood by the receiver is highlighted, using the analogy of language barriers in communication. The paragraph concludes by differentiating between local inter-process communication within a single machine and computer networks, which involve separate machines that may be geographically distant.

05:01

🔌 Inter-Process Communication vs. Computer Networks

This paragraph delves into the distinction between inter-process communication (IPC) and computer networks. It clarifies that IPC occurs within a single machine and is managed by the operating system, whereas computer networks involve separate machines that may be located in different physical locations. The paragraph emphasizes the user's perspective of seamless data access, whether it's local files or data from remote servers like Facebook or Google. It also touches on the abstraction provided by computer networks, making remote interactions feel local, and sets the stage for discussing the Open Systems Interconnection (OSI) model and the TCP/IP model in subsequent content.

10:07

🛠️ Mandatory and Optional Functionalities in Networking

The paragraph discusses the various functionalities necessary for effective data communication in computer networks. It differentiates between mandatory and optional functionalities. Mandatory functions, such as error control and flow control, are critical for ensuring data integrity and preventing network congestion. The paragraph also introduces optional functionalities like encryption-decryption (cryptography) and checkpointing, which are not required for all applications but add layers of security and efficiency where needed. The discussion highlights the balance between adding complexity to a system and the benefits of these optional features.

15:11

🔐 The OSI Model: Structuring Network Functionalities

This paragraph introduces the OSI (Open Systems Interconnection) model, a standardized framework that categorizes the various functionalities of data communication into seven distinct layers: physical, data link, network, transport, session, presentation, and application. It explains that the model serves to standardize the process of data transmission, ensuring that data sent from one machine adheres to a set of protocols that allow it to be correctly interpreted by the receiving machine. The paragraph sets the foundation for further exploration of each layer's specific roles and contributions to the communication process.

20:22

📚 Exploring the Layers of the OSI Model

The final paragraph of the script previews upcoming content that will delve into the specifics of each layer within the OSI model. It suggests an educational approach to understanding the roles and purposes of each layer in facilitating message transmission across computer networks. The paragraph also encourages viewers to engage with the content by sharing it and subscribing to the channel for further educational videos on the topic.

Keywords

💡Computer Network

A computer network is defined as a collection of computing devices connected for the purpose of sharing data. It is central to the video's theme as it sets the stage for discussing how data is transferred between devices. The video script uses the concept of a computer network to explain the mechanics of data sharing, such as the need for a sender and receiver, and the types of connections (wired or wireless) that facilitate this process.

💡Sender and Receiver

The terms 'sender' and 'receiver' are used to describe the entities in a communication process within a computer network. The sender initiates data transmission, while the receiver is the endpoint that receives the data. In the context of the video, these terms are fundamental to understanding the basic operation of a network, where the script explains that these roles can be fulfilled by machines or users operating machines, such as when a user types a message on a keyboard to be displayed on a monitor.

💡Protocol

A protocol in the context of computer networks is a set of rules governing the format and transmission of data. The video emphasizes the importance of protocols to ensure that data sent by the sender is understood by the receiver. It uses the analogy of a language barrier to illustrate the need for common protocols to facilitate communication, ensuring that the data is not only transmitted but also comprehensible.

💡Wired and Wireless Connections

These terms refer to the physical means of connecting devices within a network. Wired connections use physical cables to transmit data, while wireless connections use radio waves or other forms of electromagnetic signals. The video script mentions these as the necessary infrastructure for data to move from one device to another, highlighting the versatility of networks to accommodate different types of connections.

💡Client and Server

In the video, 'client' and 'server' are terms used to describe the roles of devices in a network. A client is a device or program that requests data or services, while a server is a device or program that provides those services. The script explains that these roles are crucial for two-way communication in a network, where the client initiates a request and the server responds with the necessary data or service.

💡Inter-Process Communication

Inter-Process Communication (IPC) refers to the exchange of data between different processes within the same machine. The video script distinguishes IPC from computer networking, explaining that IPC is managed by the operating system's kernel and is not the focus of computer network studies. It is mentioned as a concept to clarify the scope of what computer networks entail, which is communication between physically separate devices.

💡Mandatory and Optional Functionalities

These terms categorize the features and processes involved in data transmission within a network. Mandatory functionalities are essential for basic network operations, such as error control and flow control, ensuring reliable data transfer. Optional functionalities, like encryption and checkpointing, provide additional features but are not required for all network communications. The video script uses these terms to discuss the trade-offs between network complexity and the need for certain features.

💡Error Control

Error control is a mandatory functionality in networks that ensures the integrity of data during transmission. The video script explains that error control mechanisms are necessary to detect and correct any changes to the data that may occur due to noise or other interferences in the network. It is crucial for maintaining the accuracy of the data received by the destination.

💡Flow Control

Flow control is another mandatory functionality discussed in the video, which regulates the amount of data sent from the sender to the receiver to prevent overwhelming the network or the receiver's capacity to process data. The script uses the term to illustrate how networks manage data transmission to avoid congestion and ensure smooth data flow.

💡OSI Model

The OSI (Open Systems Interconnection) model is a conceptual framework that standardizes the functions of a networking system into seven layers. The video script introduces the OSI model as a way to organize and understand the complex array of functionalities involved in network communication. Each layer has specific responsibilities, from the physical transmission of data to the application-level processes that use the network.

💡Cryptography

Cryptography is the practice of secure communication, which involves the use of encryption and decryption to protect data from unauthorized access. The video script mentions cryptography as an optional functionality in networks, particularly important for applications that require a high level of security, such as online banking. It provides an example of how additional layers of security can be implemented in network communications.

Highlights

A computer network enables devices to share data.

Networks can connect homogeneous and heterogeneous devices.

The primary function of a network is data sharing.

Sender and receiver can be machines or users operating machines.

Data transmission requires a connection, which can be wired or wireless.

Protocols are essential for data understanding between sender and receiver.

An example of communication barrier is language difference in phone calls.

Computer networks facilitate communication between physically separated devices.

Client and server can be on the same machine, like a laptop.

Inter-process communication is handled by the operating system, not the computer network.

Computer networks are about connecting different machines, not just components within one machine.

The goal of computer networks is to make physically separated processes feel like they are on the same machine.

Error control is a mandatory functionality to ensure data integrity during transmission.

Flow control prevents network congestion by managing data transmission rates.

Multiplexing and demultiplexing are used to manage data from multiple processes.

Encryption and decryption are optional functionalities used for secure data transmission.

Checkpoints can be used to resume data transmission from a certain point in case of failure.

The OSI model organizes network functionalities into seven layers for standardization.

The OSI model includes physical, data link, network, transport, session, presentation, and application layers.

The OSI model helps in understanding the process of data transmission and reception in a standardized way.

Transcripts

A computer network is a collection of various computing devices

The purpose of a computer network is so that the devices can share data

Means, we have to connect the various homogeneous, heterogeneous kind of devices

The purpose of a computer network is that they can share something, the main part of a computer network is to share the data

Now, In the computer network, we are having...

One sender and one receiver

The sender is trying to send some data to the receiver,

so sender and receiver can be a machine, means it can be a user who'll be sending the data through a machine

So we can say the sender is writing a program

To send some data to the receiver... Now how it'll send the data? It needs some kind of connection

It needs some kind of connection... Connection can be like we have wire connection, wireless connections also

So whatever connection it is, whether it is wired or wireless... But first of all, we need some connection

So through the connection, the packets, the data will move from the sender machine to the receiver machine

Now, the term over there is the connection... Next is, like sender has sent some data, let's say

There's a message "M" and the sender is sending this message "M" to the receiver

Receiver gets the data, means the message "M"

Now the next part is... Sender sends the data and the receiver receives the data

But the next part is, whatever message is received by "R",

Check whether "R" is able to read or understand the data or not?

The concept says that the data which sent by the sender, it must be understood by the receiver also

For that, there must be some kind of protocol that must be running at the sender's machine

and the protocol which must be running at the receiver's machine

What is the advantage of this protocol?... The protocol is like a set of instructions,

Means the sender will send the data but it'll follow some kind of instruction

so that whatever data it is sending, the receiver must be able to understand it.

Let's say if I make a call

Let's say I know Punjabi and I called a Telegu person

So whatever I'm speaking, that person is able to hear that, he can understand that I'm saying something

But is he able to understand whatever I'm speaking

No, he's not able to understand, and I can't understand whatever he's speaking,

but I can recognize that he's sending some message

So what connection makes is, that data will be travelled from sender to receiver, or we can say receiver to sender also,

But check whether we are able to understand the data or not,

For that, there must be some kind of protocol that must be running on both sides and that's called the proper communication

Means, connection with proper protocol and set of instructions,

if they are followed, then we can say there's proper communication between the sender and the receiver

Now we are saying there's a sender, there's a receiver or in the computer network terms we use the client and server also,

means there's some kind of client and there's some kind of receiver,

so whatever client or server, or we can say sender or receiver

Where they are present? One scenario can be...

Sender or receiver or we can say client or server are both present in the same machine,

let's say there's a machine...

The Machine can be your laptop... Let's say your laptop.

In your laptop, a process generated by a client or generated by a sender is sending some message to the receiver

Let's say if I press a button from the keyboard

Whenever I press a button, the same whatever I entered... That will be printed or will be visible on the monitor

So there's some kind of process generated by the sender or a person and that message is given to the receiver

The sender is generating a process of pressing a button, whatever button it is

And the receiver... The receiver here is the monitor

Who is the sender? keyboard

But there is a single person and that same user, but the point is that there's a user process sending some kind of message

And that message is printed on the monitor

But here the concept is within the same machine, means we are talking in one machine only

Now when a process communicates with another process in the same machine then that is called the inter-process communication

But that inter-process communication is dealing with the computer network?? No

The Computer network is not dealing with that part... This part is dealt with by the operating system

The kernal in our operating system deals with this part that how a process is passing instructions or message to another process,

or how a keyboard is passing instructions or messages to the monitor

that is done by the operating system, we call it interprocess communication

There also obviously there are some wires,

If you'll check your CPU or Keyboard or your laptop, then there'll be wires at the backend through which data travels,

the concept is the same, but there's no concept of computer network,

The concept of computer network comes when the client is some other machine and the server is some other machine,

Means they can be physically separated, means they are different people or machines,

where the client and server is present on different machines, Let's say this is machine one and this is machine two

Here we can say, the concept of computer network comes

Now, if I would talk about my machine or my laptop,

there if I'd easily press some button or click the mouse then that message is coming on the monitor easily,

then it means there is a very smooth connection,

So, that same smooth connection I have to make between this client and server

And it may be possible that one client could be in India and the server can be in the USA, UK, or some other location

And I'm not talking about distance... distance can be 1km or even 1m or maybe 10,000km also

So distance doesn't matter, we are not talking about the distance here

We are saying that the client is present on some other machine, and the server is present on some other machine

In that case, can I make a smooth connection like that and can communicate smoothly?

For making that smooth, we use the concept of computer networks

Means, let's say this is my machine and I'm present in India

And this is some other machine and it is present in USA

Now my client's machine is sending some data to the server, Let's say I'm opening my Facebook account

So if I opened my Facebook account... I'm not going into much detail about computer networks for now

I'm starting with the very basic level that we generally use daily

We open Google, Facebook, daily... Even at present time, Google is that much famous

that even if we want to check if our internet is working or not, for that too we open Google

That's the fame of Google... So what we are checking in Google or Facebook?

We are sending a message from our machine to the Facebook

So there's a server of Facebook which is present in the USA and my message is reaching there

But here, me who is the user... We have to give an environment to both of these machines

Means we have to provide such an environment that they won't get feel that they are two different machines

And this is what we generally feel... When I log in to Facebook through my machine

Or when I use WhatsApp or Google, we feel like how fast the data has arrived... I mean we feel like the data is already on our laptop

This is how fast the data get accessed... Like if there are movies in hard disk in C drive, D drive etc.

Now if I access movies in the D drive...

I clicked play on movie and the movie started running through VLC, it takes hardly a few seconds

And same time it takes to access data from Facebook or Google

So what is this? We are trying to make some scenario, there we are not saying that we are calling data from the USA or UK,

because we don't know this thing, this is a kind of abstraction for us,

so at that point, the computer network is making my process and server's process feel that both are present in the same machine

But actually, they are not present

So the functionality of a computer network is that

the client and server which are physically separated should feel that they are present in the same machine.,

Both processes should feel that they are in the same machine, but they are actually not

So the computer network provides this functionality and that is the main function

Now this data that we are sending to the server, calling the data from the server, the server can also reply,

Obviously, if I have requested that I need some data from Google or from my Facebook account,

then obviously, server will also respond to me with the data, so we use a lot of functionalities in this two way communication

Generally, what kind of functionalities are used?

Let's say

There are basically two kinds of functionalities

One is the mandatory

And some are optional

Mandatory... Mandatory means that whenever my client machine is sending some data or request to the server,

then what are the mandatory functions... That we can't neglect those functions

An example of that function can be... Let's say, the one and very important is an error control

Error control means the message that I'm sending to the receiver or to some other machine

Is the same message being sent there or some other message is being sent there

because, at present time, the lot internet that we are using is an open system

so it's possible that there could be some problem in the message in between, due to some noise or hacking... Whatever the factor

So my message that's going here which I'm sending, whatever message i.e. "M"

Which I'm sending... the receiver is receiving "M" or "M1"

Obviously, if I've sent "M" messages then the receiver should also receive an "M' message

But due to noise or some other factor, it can be changed... Means at least I can know that there is some kind of error

So in my mechanism, there should be a lot of functionalities that should tell me that there's some kind of error

Means at least I can find out that there's some kind of error

Or if I'll find the error then later I can make it correct also or I can also resend the data, so that is some other thing

So, one kind of functionality is error control and another kind of functionality is flow control

Flow control means the amount of data,

means as a sender I'm sending some data to the receiver and I filled the whole network with data... No, there is some kind of flow control

Means it shouldn't be like that I filled the whole buffer and filled its all memory

There is some kind of constraint over there, if we are using that constraint,

only then my network will flow properly otherwise there could be chances of congestion

Means, the protocols of my system running will provide me with these mandatory functionalities

Another can be, let's say one more... Let's say multiplexing and demultiplexing

Multiplexing-Demultiplexing means, let's say a lot of programs are running in my machine... Means a lot of processes are going on

Means if I'm working on some web browsers or downloading something on different web browsers or whatever I'm doing

A lot of different processes are going on

Now out of all those processes, which process is sending the data

Like in my machine, a lot of processes are going on

Out of those, whichever process is sending the data, that helps me in multiplexing and demultiplexing

This is basically a transport layer funda which we will discuss in detail later

and the same way if a message is coming on my machine

like if I'm getting a message on my laptop, like if got an Email,

then, to which particular process it should go

That is also the main point, so we have kept that kind of functionality as mandatory also

Same way, let's say a lot of functionalities are there in the mandatory

Let's say now, optional... In optional

the major functionality comes is encryption-decryption

which we call cryptography also... Cryptography means we are not sending the data as it is,

we are trying to send it in some other form so that any intruder in the middle cannot understand that data

But, not all application requires the encryption-decryption

Nowadays, there are a lot of applications like a banking application, wherever I'd talk about money transfer

There we definitely need some kind of encryption method, so that no intruder can hack the data in the middle

But obviously this increase system's complexity

Because normal algorithms are working fine, these all are algorithms,

Coding of all of these are already present in our kernal or operating system and it provides all these mandatory functions

Along with that If I'd do coding of optional functions also in the middle then obviously the system's complexity will increase

Then my time to send the data will also increase

So this is a very main point, but wherever I'd feel the need

Means if we send data on normal http then not required...

But https, that encrypts the data and then sends it, then there I'll definitely need encryption

So if we are sending the data normally where we don't need any security or cryptography, then I can simply send the data

Same way... Let's say checkpoint

Checkpoint means that when we are downloading the data, then there are checkpoints after a certain amount of time

Let's say I have a 500MB file and I'm downloading that data,

let's say when that file downloaded 301MB, downloading is still going on but it got failed at 301MB

So next time I'll do download again, then it should not start from zero

It should start again from 301... or maybe some lower value, let's say I'm putting checkpoint after every 100MB

So the moment my downloading will get failed then it'll start again from 300

But, is it required for all applications? No

If we are calling very small amount of data at some place like we are sending message on WhatsApp

so we are sending messages on WhatsApp in bites only, so I don't need checkpoint there

So it's much better if I won't add extra functionalities there, because it'll make the system much more complex

So here we are discussing this concept because we are moving to next OSI model

So there are a lot of functionalities in optional and mandatory which are more than 70

More than 70 functionalities are there

So they made a standard model of all these functionalities

We generally discuss in networks, the concept of OSI model comes in starting

TCP IP model and OSI model both are there... And you may have its a lot of videos & material available also

But there, no one tell us that why there is a need of OSI model because it is a theoretical model

But what is the need of that model? Why we are implementing that model and what is its need?

The reason behind that model is this... That all these functionalities that we are providing,

we decided all these functionalities in a model that whenever data will be sent in my laptop, it will be those this model

This is the standardised model....

It means I'll follow a standard or protocols and after following those protocols my message will go out of my machine

And same way , when that message is entering in the receiver's machine, then it'll follow those protocols before reaching to the user

so for all this we make a model here and it's a very standard model i.e. OSI (Open system Interconnect)

That's an OSI model... Now what we did in an OSI model, we converted all these functionalities in layers.. How?

Standard layers of OSI model are... There are 7 layers

First one is the physical layer

Above physical layer comes the data link layer

then network layer

Transport layer

Session layer

Presentation

and application

So these 7 layers are the heart of the OSI model

So all the functionalities I have... Around 70 functionalities are there

They simply divide in each of the layer

So whenever my message will be sent by my machine

Whenever I'll send a message then it'll pass through all the layers

This is the concept of the OSI model

So the OSI model is fulfilling all the functionalities that are there

There are many more models other than this, like the TCP IP model which is also very important

IEEE model is also very important... But from our GATE point of view or normal academically, we follow only these two protocols

So in the next videos, we'll take each layer one by one

that what are their functionalities and what is their purpose in our system and how they help in sending the message

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