Understanding Computer Networks

A computer network is a collection of various computing devices. The purpose of a computer network is so that the devices can share data. We have to connect various homogeneous and heterogeneous kinds of devices. The main part of a computer network is to share data. In the computer network, we have one sender and one receiver. The sender is trying to send some data to the receiver. The sender and receiver can be machines or users sending data through machines.

Data Transmission and Connection

The sender writes a program to send some data to the receiver. To send the data, a connection is needed. The connection can be wired or wireless. Through the connection, packets of data move from the sender machine to the receiver machine. The key term here is “connection.” The sender sends a message, say “M,” and the receiver gets the data, which is the message “M.”

Protocols and Communication

The next part is checking whether the receiver can read or understand the data. For this, there must be a protocol running on both the sender’s and receiver’s machines. A protocol is a set of instructions that ensures the data sent by the sender can be understood by the receiver.

Imagine making a call where you speak Punjabi to someone who speaks Telugu. The person might hear you but not understand you. Similarly, the connection ensures that data is transmitted from sender to receiver. But for proper communication, there must be a protocol and set of instructions followed. Proper communication between sender and receiver requires a connection with a proper protocol.

Client and Server Communication

In computer network terms, the sender and receiver can also be referred to as client and server. A scenario can be that the client and server are on the same machine, like a laptop. For example, pressing a button on the keyboard prints the text on the monitor. Here, the process of pressing a button is generated by the sender (keyboard), and the monitor is the receiver. This is within the same machine.

Inter-Process Communication vs. Computer Network

When a process communicates with another process within the same machine, it is called inter-process communication. However, this is dealt with by the operating system, not the computer network. The operating system’s kernel manages how a process passes instructions or messages to another process. The concept of computer networks comes into play when the client and server are on different machines.

Remote Communication

When the client and server are physically separated, like one in India and the other in the USA, the concept of a computer network is used. Distance doesn’t matter; what matters is the smooth communication between the client and server. For example, when you open Facebook, the data is sent from your machine to Facebook’s server in the USA. The computer network creates an environment where the client and server feel like they are on the same machine.

Functions of Computer Networks

The functionality of a computer network ensures that the client and server, though physically separated, function as if they are on the same machine. The server replies to requests made by the client. There are mandatory and optional functionalities in computer networks.

Mandatory Functionalities

1. Error Control: Ensures that the message sent is the same as received. Error control mechanisms detect any changes in the message due to noise or hacking. If errors are detected, they can be corrected or the data can be resent.
2. Flow Control: Manages the amount of data sent to avoid overwhelming the receiver or causing congestion in the network.
3. Multiplexing and Demultiplexing: Manages multiple processes sending and receiving data. It helps in directing data to the correct process on the receiving end.

Optional Functionalities

1. Encryption-Decryption (Cryptography): Encrypts data to prevent unauthorized access, essential for secure applications like banking. Encryption increases system complexity and time for data transmission.
2. Checkpointing: Allows resuming data transfers from the last successful point if a transfer fails, useful for large file downloads. Not necessary for small data transfers.

The OSI Model

The OSI (Open System Interconnection) model is a standard model used to divide functionalities into layers. There are 7 layers in the OSI model:

1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer

Each layer of the OSI model handles specific functionalities. The OSI model ensures that all functionalities are standardized and allows data to pass through each layer.

Conclusion

The OSI model provides a framework to standardize communication functions and ensure that data is sent and received correctly. Next, we will explore each layer of the OSI model in detail, discussing their functions and purposes.