History of the Internet
1969 – ARPANET (Advanced Research Projects Agency Network) was created by the U.S. Department of Defense, marking the beginning of modern networking.
1971 – ARPANET grows and connects more institutions; the first network email is sent.
1983 – ARPANET adopts the TCP/IP protocol, which becomes the standard for future networks.
1986 – NSFNET (National Science Foundation Network) is launched to connect and support academic research across the U.S.
1990 – ARPANET is decommissioned, having served as the foundation of today’s internet.
1991 – The World Wide Web becomes publicly available, developed by Tim Berners-Lee.
1995 – NSFNET is decommissioned, and the internet becomes fully commercialized.
2000s – Present – The Internet expands globally, enabling services like cloud computing, IoT, and social networking.
What is the Internet?
The Internet is a global computer network providing a variety of information and communication facilities, consisting of interconnected networks using standardized communication protocols.
A Computer Network is a set of computers connected together for the purpose of sharing resources.
Types of Networks
Computer Network
│
├── Wired Network
│ ├── Single Hop (e.g., Ethernet)
│ └── Multi Hop
│
└── Wireless Network
├── Purely Wireless
│ ├── Single Hop (e.g., Bluetooth)
│ └── Multi Hop (e.g., Ad-hoc Networks)
└── Wired cum Wireless
├── Single Hop (e.g., Wi-Fi)
└── Multi Hop (e.g., GSM)NIC (Network Interface Card)
A Network Interface Card (NIC) is a hardware component that enables a computer or other device to connect to a network. It acts as a bridge between the device and the network by sending and receiving data.
Functions:
Converts data into electrical, optical, or radio signals.
Connects via Ethernet or wirelessly (Wi-Fi).
Typically installed on the motherboard or connected externally.
Types of NICs:
Wired NIC – Uses Ethernet cables (e.g., RJ-45 connector).
Wireless NIC – Uses radio signals to connect (Wi-Fi).
Integrated NIC – Built directly into the motherboard.
External NIC – USB or expansion card NICs.
Note: Each NIC has a unique MAC address used to identify the device on the network.
Cables:
Straight-Through Cable – Used to connect different devices (e.g., PC to switch).
Cross-Over Cable – Used to connect same devices (e.g., PC to PC, switch to switch).
MAC (Media Access Control) Address
A MAC address is a unique identifier assigned to a device's NIC, used to identify devices at the data link layer (Layer 2) of the OSI model. Used by switches and bridges for data forwarding within LAN.
48-bit (6 bytes) hexadecimal address seperated by : or -, shown as: 00:1A:2B:3C:4D:5E
Basic Format has two parts:
OUI (Organizationally Unique Identifier) – First 24 bits (identifies manufacturer).
Device Identifier – Last 24 bits (device-specific/ Unique to device).
Permanently assigned by manufacturer, burned into hardware/ ROM (but can be spoofed using software).
Types of MAC Addressing:
Unicast – Sent to a specific device.
Multicast – Sent to a group of devices.
Broadcast – Sent to all devices (
FF:FF:FF:FF:FF:FF).
MAC Address Commands:
Windows:
getmac,ipconfig /allLinux/macOS:
ifconfig,ip link, orip a
MAC Filtering:
Routers can use MAC filtering to allow or deny specific devices access to the network.
Internet Protocol (IP)
Internet Protocol (IP) is the network protocol used to deliver packets of data across networks.
It defines the rules and structure for how data should be packaged, addressed, transmitted, and routed between devices.
IP operates at Layer 3 (Network Layer) of the OSI model.
Internet Protocol Address (IP Address)
An IP address is a numerical label assigned to each device connected to a network that uses the Internet Protocol (IP) for communication.
It uniquely identifies devices and facilitates routing of data between the sender and receiver across local networks or the internet.
Main Functions of an IP Address:
Network Identification (NID) – Identifies the network segment to which the device belongs.
Host Identification (HID) – Identifies the specific device within that network segment.
- IP addresses are essential for proper communication between devices on both local and wide area networks (LANs and WANs).
Versions of Internet Protocol Address (IP Address Versions)
Several versions of IP have been defined. Some are in use today, while others were reserved or experimental.
IP Versions:
IPv1 to IPv3:
Early development versions that were never officially deployed.IPv4:
The most widely used version of IP, based on a 32-bit addressing system.IPv5:
An experimental protocol known as Internet Stream Protocol.
It was never officially adopted or publicly implemented.IPv6:
The modern version of IP, designed to address the limitations of IPv4, using a 128-bit addressing scheme to support vastly more addresses.IPv7 to IPv15:
These are either reserved, experimental, or unused in public implementations.
Classes of IP Addresses (IPv4)
IPv4 addresses are categorized into five different classes based on their starting bits and address ranges. This classification helps in defining the size of networks and how many hosts (devices) they can support.
An IPv4 address is 32 bits long and divided into 4 octets (8 bits each).
The total IPv4 address space is 2³² = 4,294,967,296 unique addresses.
IPv4 addresses are represented in:
Binary notation (e.g.,
11000000.10101000.00000001.00000001)Dotted-decimal notation (e.g.,
192.168.1.1)
Although IPv6 adoption is increasing, IPv4 is still widely used today.
IPv4 Class A Address
First bit (MSB) is always 0.
Range:
1.0.0.0to126.255.255.255127.0.0.0is reserved for loopback (used for testing and diagnostics).
Class A Characteristics:
Total networks: 2⁷ = 128, but only 126 usable (excluding 0 and 127).
Hosts per network: 2²⁴ − 2 = 16,777,214 (subtracting 2 for:
Network address (all host bits = 0)
Broadcast address (all host bits = 1)
Use Case: Large networks such as governments and multinational organizations.
Default Subnet Mask:
255.0.0.0
IPv4 Class B Address
First two bits are 1 and 0.
Range:
128.0.0.0to191.255.255.255
Class B Characteristics:
Total networks: 2¹⁴ = 16,384
Hosts per network: 2¹⁶ − 2 = 65,534
Use Case: Medium to large-sized organizations, such as corporate companies.
Default Subnet Mask:
255.255.0.0
IPv4 Class C Address
First three bits are 1, 1, and 0.
Range:
192.0.0.0to223.255.255.255
Class C Characteristics:
Total networks: 2²¹ = 2,097,152
Hosts per network: 2⁸ − 2 = 254
Use Case: Small organizations, such as colleges or small businesses.
Default Subnet Mask:
255.255.255.0
IPv4 Class D Address
First four bits are 1, 1, 1, and 0.
Range:
224.0.0.0to239.255.255.255
Class D Characteristics:
Not used for traditional NID/HID addressing.
Used for Multicasting, not unicasting.
Suitable for sending data to multiple recipients simultaneously.
IPv4 Class E Address
First four bits are 1, 1, 1, and 1.
Range:
240.0.0.0to254.255.255.255
Class E Characteristics:
Not used for standard networking.
No NID or HID structure.
Reserved for research and development purposes.
Private IP Address
A private IP address is an IP address used within an internal network (e.g., home, school, office).
These addresses are not routable on the public internet.
Devices using private IPs can access the internet through a router that uses NAT (Network Address Translation).
NAT allows multiple devices to share a single public IP address when communicating with external networks.
Common Private IP Address Ranges (IPv4):
| Class | Range | Subnet Mask |
|---|---|---|
| A | 10.0.0.0 – 10.255.255.255 | 255.0.0.0 |
| B | 172.16.0.0 – 172.31.255.255 | 255.240.0.0 |
| C | 192.168.0.0 – 192.168.255.255 | 255.255.0.0 |
These private ranges are reserved by IANA (Internet Assigned Numbers Authority) and cannot be assigned on the public internet.