The Internet is a global network of computers connected together.
When you open Google → your computer connects to Google’s server through the Internet.
The network edge is where users connect to the Internet. The Network Edge
How devices connect to the Internet.
Types:
The actual medium used to transmit data
Types:
The Network core is the backbone of the Internet (high-speed routers and links).
Data is broken into small pieces called packets.
Used in the Internet.
Example: Sending WhatsApp message → divided into packets → reassembled
A dedicated path is established before communication
Less efficient than packet switching
| Feature | Packet Switching | Circuit Switching |
|---|---|---|
| Connection | No dedicated connection | Dedicated connection required |
| Data Transmission | Data sent in small packets | Data sent as a continuous stream |
| Path | Packets may take different paths | Fixed path for entire communication |
| Efficiency | High (uses bandwidth efficiently) | Low (bandwidth reserved even if unused) |
| Delay | Variable delay (depends on network) | Constant delay once connection established |
| Setup Time | No setup required | Requires setup time before transmission |
| Reliability | Packets may be lost or arrive out of order | Reliable, ordered delivery |
| Cost | Cheaper | Expensive |
| Example | Internet, email | Traditional telephone system |
Time taken for data to travel from sender to receiver
Types:
When data packets are lost during transmission. Network congestion may be the reason for data packet loss.
Amount of data transferred per second
Protocol layers mean dividing network communication into different levels, where each layer has a specific task. Each layer works separately but together they complete the communication process.
Why layers are used:
Example (TCP/IP model):
Encapsulation is the process of adding extra information (called headers) to data as it moves from one layer to another.
Simple idea:
Process of adding headers at each layer
📦 Like packing a parcel:
A service model defines what type of service one layer provides to the layer above it.
Types of services:
The development of computer networking and the Internet happened step by step over time.
Computers were very large and expensive. They were not connected to each other. People used them individually.
Later, the idea of connecting computers started for sharing data and resources.
The first real computer network was called ARPANET, developed in the United States.
Scientists developed communication rules called protocols.
The most important was TCP/IP.
The Internet became popular worldwide.
Tim Berners-Lee introduced the World Wide Web.
The Internet is now used everywhere.
Two types:
Note:
Email contains:
Used to receive emails
Types:
Note:
No central server → users share files directly
Watching video without downloading fully
Examples:
Servers distributed across world
Purpose:
When you watch Netflix:
Points to Know
A Personal Area Network (PAN) is a small network used to connect devices around one person within a short distance.
It is mainly used for personal devices such as:
The coverage area of a PAN is usually a few meters.
Bluetooth is the most common technology used in a Personal Area Network. It allows devices to communicate wirelessly over short distances without using cables.
For example:
Bluetooth works by creating a wireless link between nearby devices.
First, devices go through a process called pairing. Pairing allows two devices to recognize and trust each other. After pairing, they can exchange data.
Bluetooth can be used for:
Bluetooth is used in many networking situations such as:
Cellular networks are wireless communication systems that divide a large area into small sections called cells. Each cell has a base station or cell tower that provides network service to mobile users. When you move from one cell to another, the connection is transferred automatically, which is called handover.
In data communication, cellular networks allow devices like phones, tablets, and laptops to send and receive data through radio waves instead of cables.
4G means Fourth Generation mobile network technology. It was introduced to provide faster internet speed than 3G.
4G can provide:
5G means Fifth Generation mobile network technology. It is more advanced than 4G and is designed for very fast speed, very low delay, and huge device connectivity.
5G can provide:
Difference Between 4G and 5G
| 4G | 5G |
|---|---|
| Fourth Generation technology | Fifth Generation technology |
| Fast internet speed (10–100 Mbps) | Ultra-fast speed (100 Mbps–1 Gbps+) |
| Example: HD video streaming works smoothly | Example: 4K/8K streaming and cloud gaming without buffering |
| Higher latency (30–50 ms) | Very low latency (1–10 ms) |
| Example: Small delay in video calls | Example: Real-time remote surgery, instant response |
| Limited device connection | Massive device connection |
| Example: Slows down in crowded areas | Example: Works well in stadiums with thousands of users |
| Uses LTE technology | Uses Massive MIMO and Beamforming |
| Example: Normal signal coverage | Example: Focused signal directly to user for better speed |
| Lower data capacity | Very high data capacity |
| Example: Network congestion during peak hours | Example: Handles heavy traffic easily |
| Suitable for normal mobile usage | Suitable for advanced technologies |
| Example: Social media, browsing | Example: Smart homes, IoT devices, self-driving cars |
| Lower bandwidth | Very high bandwidth |
| Example: Limited data transfer rate | Example: Faster download of large files in seconds |
| Wide coverage | Limited coverage (especially mmWave) |
| Example: Works in rural areas | Example: Best performance in cities with 5G towers |
| Less energy efficient | More energy efficient |
| Example: Higher battery/network load | Example: Optimized power usage for connected devices |
The OSI (Open Systems Interconnection) Reference Model is a conceptual framework developed by ISO (International Organization for Standardization) to standardize network communication. In 1984, ISO officially introduced the OSI Reference Model.
The OSI model was created to make network communication simple, standard, and flexible. It provides a structured way to understand how data moves from one system to another and helps in developing and implementing networking protocols.
The OSI model was developed by ISO in 1984 to standardize network communication. It divides networking functions into seven layers, each performing specific tasks. The main purpose of the OSI model is to enable interoperability between different systems, simplify network design, and help in understanding and troubleshooting networks.
The Application layer is the topmost layer of the OSI model and acts as the interface between the user and the network. It provides network services directly to user applications. This layer does not provide services to other OSI layers but instead offers services such as file transfer, email, remote login, and web browsing. It allows users to access network resources and handles user authentication and service availability.
The Presentation layer is responsible for data representation and translation. It ensures that data sent by the sender is readable by the receiver. This layer handles data format conversion, encryption for security, and compression to reduce data size. It acts as a translator between different systems.
The Session layer establishes, manages, and terminates communication sessions between applications. It controls dialog management and synchronization between systems. This layer ensures that data exchange happens smoothly by setting checkpoints and maintaining sessions during data transfer.
The Transport layer is responsible for reliable data transfer between systems. It breaks data into smaller segments, performs error detection and recovery, and ensures data is delivered in the correct sequence. This layer controls flow and congestion and uses protocols like TCP and UDP.
The Network layer handles routing and logical addressing of data packets. It determines the best path for data to travel from the source to the destination across multiple networks. This layer uses IP addresses and is responsible for packet forwarding, routing, and congestion control.
The Data Link layer ensures error-free transmission of data between two directly connected nodes. It packages raw data into frames and uses physical (MAC) addresses for device identification. This layer also handles error detection, flow control, and access control to the physical medium.
The Physical layer is responsible for the transmission of raw bits over the communication medium. It defines hardware specifications such as cables, connectors, voltage levels, and transmission speed. This layer deals with the physical connection between devices.
The Network Layer –
The Network Layer is the 3rd layer of the OSI Model.
Its main job is to move packets from source to destination across multiple networks.
It is responsible for:
4.1 Data Plane
The Data Plane (also called Forwarding Plane) is responsible for:
Key Functions:
Think of a bus station:
Forwarding is different from routing.