1.3.3 Network Hardware

Connecting devices together to form a network requires both network hardware and a way for data to travel between devices.

Different components perform different jobs. A network interface controller (NIC) allows a device to connect to the network, transmission media carry the data, switches connect devices within a LAN, wireless access points allow wireless devices to join the network, and routers connect different networks together.

Figure 1 shows how these components can work together in a typical LAN. Wired devices connect to the switch using network cables, while wireless devices connect to the Wireless Access Point (WAP) using Wi-Fi. The WAP itself is connected to the switch so that wireless devices can communicate with the rest of the LAN.

The router connects the LAN to other networks, such as the internet. The connection between the router and the wider network is shown as a wired or physical network connection in the diagram, although the exact transmission medium used by an internet service provider may vary, for example fibre-optic or copper cable, which are explored later in this lesson.

Each end device also requires a NIC so that it can send and receive data over the network. In Figure 1, the NICs are shown next to the wired devices to make their role visible, but in modern computers the NIC is usually built into the device rather than being a separate external component.

A Network Interface Controller (NIC) is the hardware interface that allows a device to connect to and communicate over a network. Computers, laptops, printers and other networked devices require some form of NIC before they can send or receive data across the network.

In modern devices, the NIC is usually built into the motherboard rather than being a separate card. A device may have a wired NIC, such as an Ethernet interface, a wireless NIC that sends and receives radio signals, or both.

The NIC prepares outgoing data for transmission across the network and receives incoming network data so that it can be processed by the device. Every NIC has a Media Access Control (MAC) address, which uniquely identifies that network interface when data is transmitted within a local network. MAC addresses are covered in Lesson 1.3.6 Wired and Wireless Networks.

Transmission media is the means by which data travels between devices on a network. Network communication can be wired, using physical cables, or wireless, using radio waves.

The transmission medium used can affect the network's bandwidth, reliability, range and susceptibility to interference. Range is the maximum distance over which a connection can transmit data effectively, while interference is unwanted disruption that can weaken or distort a transmitted signal.

Copper Cables

Copper network cables transmit data using electrical signals. Two examples are twisted-pair cable and coaxial cable.

Ethernet networks commonly use twisted-pair cables, which contain pairs of copper wires twisted together. Twisting the wires helps reduce interference from other electrical signals, making data transmission more reliable. Twisted-pair Ethernet cables usually connect devices to switches, routers or other network equipment using Ethernet ports.

Copper cables are widely used within LANs because they are relatively inexpensive and can provide fast, reliable connections over short distances. However, their useful range and bandwidth are more limited than fibre-optic cable.

Because copper carries data using electrical signals, nearby electrical or magnetic fields can disrupt those signals. This is known as electromagnetic interference, and it can reduce the reliability of data transmission.

Another type of copper cable is coaxial cable. A coaxial cable contains a central copper conductor surrounded by insulation and shielding, which helps protect the signal from interference. Coaxial cables are commonly used for services such as cable broadband and television, although twisted-pair cables are more commonly used to connect devices within modern Ethernet LANs.

Fibre-Optic Cables

Fibre-optic cables contain thin strands of glass or plastic and transmit data using pulses of light rather than electrical signals.

Fibre-optic connections can provide very high bandwidth and transmit data over much greater distances than copper cables. Because the data is carried as light, fibre is also not affected by electromagnetic interference.

Fibre-optic cables are therefore commonly used for high-speed network connections and for carrying data over long distances, including connections between different networks and locations.

Wireless Transmission

Wireless networks transmit data using radio waves rather than physical cables. Technologies such as Wi-Fi allow devices such as laptops, tablets and smartphones to communicate wirelessly.

Wireless connections make it easy to move devices around and connect new devices without installing cables. However, wireless signals become weaker over distance and can be affected by physical obstacles and interference from other wireless signals.

This means a wireless connection may be less stable or provide lower performance than a good wired connection in some situations.

A network switch connects multiple wired devices together within a LAN. Devices such as computers, printers, servers and wireless access points can connect to ports on the switch.

A switch contains several physical network ports, usually Ethernet ports. Each wired device connects to one of these ports using a network cable. This allows the switch to receive data from one connected device and forward it through the appropriate port towards the intended destination.

A switch learns the MAC addresses of the devices connected to it. When data arrives, the switch examines the destination MAC address and forwards the data towards the intended device rather than sending it unnecessarily to every device on the network. This reduces unnecessary network traffic and allows devices on the LAN to communicate more efficiently.

A Wireless Access Point (WAP) allows wireless devices to connect to a network using Wi-Fi. It communicates wirelessly with devices such as laptops, tablets and smartphones and is usually connected by cable to a network switch on the wired LAN.

A WAP normally broadcasts a Service Set Identifier (SSID), which is the name of the wireless network that users see when choosing a Wi-Fi connection. Multiple WAPs can also be used to provide wireless coverage across a larger building or site.

A router connects different networks together and forwards data between them. A common example is a router connecting a home or school LAN to the internet.

Data sent across a network is commonly divided into smaller units called packets. Each packet contains part of the data along with information needed to help it reach its destination.

When a router receives a data packet, it examines the destination IP address to determine which network the packet needs to reach. It then forwards the packet towards the appropriate network or next router on its journey.

Routers can therefore be thought of as directing traffic between networks, whereas switches mainly forward data between devices within the same LAN.

In many homes, the device commonly called a router actually combines several pieces of network hardware in one unit. It may contain a router, a small switch and a wireless access point. Such a device performs several network roles even though it appears to be one piece of hardware.