Internet and Networking

Devices on a network need an address so that data can be sent to the right one. Two addressing schemes are examined: MAC and IP.

MAC address

The MAC address (short for Media Access Control) acts as a unique identifier for each network card. The manufacturer burns it into the NIC during production, and it is used to recognise the device on a Local Area Network (LAN).

Key facts:

• Static: the MAC address is set at the factory and never changes for the life of the NIC.
• 48 bits long, usually written as 12 hexadecimal digits grouped into six pairs separated by colons: AA:BB:CC:DD:EE:FF.
• The first three pairs identify the manufacturer (Organisationally Unique Identifier, OUI).
• The last three pairs are a serial number assigned by the manufacturer.
• A device's MAC address stays the same even after the device joins a new network.
• The 48-bit address space allows for about 281 trillion different MAC addresses, far more than the number of devices ever made.

IP address

An IP (Internet Protocol) address is a unique identifier assigned to a device when it joins a network, used to identify the device on the internet (WAN).

Key facts:

• Can be static (fixed, used for servers and websites that need a permanent location) or dynamic (changes each time the device joins a network, assigned automatically by a DHCP server).
• A device's IP address typically changes whenever it joins a different network.
• Two versions exist: IPv4 and IPv6.

IPv4

IPv4 is the older version, using 32-bit addresses written as four denary numbers in the range 0 to 255, joined by dots.

Example: 192.168.1.1

• Each block (called an octet) is one byte (8 bits).
• A full IPv4 address occupies 32 bits in total (4 bytes).
• The total number of possible IPv4 addresses is 2³² ≈ 4.3 billion.
• That seemed like plenty in 1983, but with 8 billion+ people, smart phones, IoT devices and servers, the 4.3 billion addresses are now exhausted.

IPv6

IPv6 is the newer version, using 128-bit addresses written as eight blocks of four hexadecimal digits, separated by colons.

Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334

• Every block holds 16 bits (2 bytes).
• The full IPv6 address spans 128 bits (16 bytes) overall.
• The total number of possible IPv6 addresses is 2¹²⁸ ≈ 3.4 × 10³⁸, enough to give every person on Earth about 10²⁸ unique addresses.
• IPv6 is now being rolled out worldwide alongside IPv4.

Side-by-side comparison

Why both addresses are needed

The two address systems do different jobs:

• The IP address gets a packet from a sender, somewhere on the internet, to the destination network. Routers around the world use it.
• The MAC address then delivers the packet within the destination network, from the router to the specific device. Switches use it.

Think of it like postal delivery: the IP address is the street address of the building, while the MAC address is the specific person's name on that floor.