Internet and Networking

Every network needs a small set of physical components. The IGCSE syllabus names five of them.

Network Interface Card (NIC)

A Network Interface Card (NIC) is the piece of hardware inside a device that lets it connect to a network.

• Every computer, phone, printer or smart-home device with networking has a NIC.
• A NIC can be wired (Ethernet socket) or wireless (Wi-Fi antenna).
• The NIC is the part that physically sends and receives data over the network.
• Each NIC carries a unique MAC address burned in at manufacture (covered in section 4).

Router

A router is a device that forwards data packets between different networks.

The router's main jobs:

• Connect a Local Area Network (LAN) to the wider internet (WAN) so home or office devices can reach the outside world.
• Read each packet's destination IP address and decide which neighbouring router or device to forward it to next, using a routing table.
• Assign IP addresses to the devices on its LAN, usually via the DHCP protocol.
• Manage and prioritise traffic so the network stays responsive when many devices are using it.
• Convert between protocols if needed.

The home box from an internet provider is a router (often combined with a switch and a wireless access point in one unit).

Switch

A switch is a device that connects multiple devices on the same LAN and forwards packets only to the specific device that needs them.

Switches read each packet's destination MAC address and send the packet only out of the port leading to that MAC. This is more efficient than the older hub, which simply broadcast every packet out of every port.

Wireless Access Point (WAP)

A Wireless Access Point (WAP) is a device that lets wireless devices join a wired network.

A WAP plugs into a wired network and broadcasts a Wi-Fi signal, letting laptops, phones and smart-home devices connect without cables. Modern home routers usually have a WAP built in.

Transmission media

The physical pathways down which the data travels:

• Copper twisted pair (the standard Ethernet cable): cheap, easy to install, lower speeds than fibre.
• Fibre optic: pulses of light through a glass thread; very fast, low signal loss, used for high-speed and long-distance links.
• Wireless (Wi-Fi, cellular): convenient but slower and more vulnerable to interference.

The five components at a glance