2.1 Networks including the internet

Explain the use of IP addresses in the transmission of data over the internet

In the context of the internet, devices need a unique way to be identified so that data can be sent to the correct destination. This is where IP addresses come into play. An IP address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It acts like a postal address for your device on the internet.

What is an IP Address?

An IP address is a unique identifier assigned to a device participating in an IP network. There are two main versions of IP addresses currently in use:

• IPv4: Uses a 32-bit numerical address, typically represented in dotted decimal notation (e.g., 192.168.1.1).
• IPv6: Uses a 128-bit numerical address, offering a much larger address space than IPv4. It's represented using hexadecimal notation (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).

Purpose of IP Addresses

IP addresses serve several crucial purposes in data transmission:

• Identification: They uniquely identify each device on the network.
• Routing: Routers use IP addresses to determine the best path to send data packets to their destination.
• Addressing: They provide a means to address data packets correctly, ensuring they reach the intended recipient.
• Network Management: Administrators use IP addresses for network management and configuration.

How IP Addresses are Used in Data Transmission

When you send data over the internet, the process involves several steps where IP addresses play a vital role:

1. Sending Device: The sending device (e.g., your computer) has an IP address. When you initiate a connection (e.g., visiting a website), your device creates data packets.
2. Packet Creation: Each data packet is encapsulated with the source IP address (your device's IP) and the destination IP address (the website's server's IP).
3. Routing: The packet is sent to your local network's default gateway (usually your router). The router examines the destination IP address and uses routing tables to determine the next hop towards the destination.
4. Inter-routers: The packet travels through multiple routers, each examining the destination IP address and forwarding the packet closer to its destination. Each router makes a routing decision based on its routing table.
5. Destination Device: Finally, the packet reaches the destination device (e.g., the web server). The destination device uses the destination IP address to identify itself and process the packet.

IP Address Structure (IPv4 Example)

An IPv4 address is typically represented as four octets (groups of 8 bits) separated by dots. Each octet can range from 0 to 255.

Octet	Value	Range
First Octet	192	0 - 255
Second Octet	168	0 - 255
Third Octet	1	0 - 255
Fourth Octet	1	0 - 255

The IP address 192.168.1.1 is therefore a valid IPv4 address.

Public vs. Private IP Addresses

IP addresses are often categorized as either public or private:

• Public IP Addresses: These are globally unique addresses assigned to devices directly connected to the internet. Your internet service provider (ISP) typically assigns a public IP address to your router.
• Private IP Addresses: These are used within a private network (e.g., your home or office network). They are not globally unique and are often used for devices behind a router. Common private IP address ranges include 192.168.x.x, 10.x.x.x, and 172.16.x.x - 172.31.x.x.

Figure