What you'll learn
This revision guide covers the essential network hardware components and connection types required for CIE IGCSE Computer Science. You will understand the function and purpose of routers, switches, hubs, network interface cards (NICs) and wireless access points (WAPs), along with the differences between wired and wireless connections. These concepts form a foundation for understanding how devices communicate within networks and connect to the internet.
Key terms and definitions
Router — a network device that forwards data packets between different networks, typically connecting a local area network (LAN) to the internet by assigning local IP addresses and managing traffic between networks
Switch — a network device that connects multiple devices within a LAN and uses MAC addresses to forward data only to the intended recipient device on the network
Hub — a basic network device that broadcasts incoming data packets to all connected devices regardless of the intended recipient, creating unnecessary network traffic
Network Interface Card (NIC) — a hardware component that allows a device to connect to a network, providing either wired (Ethernet) or wireless connectivity with a unique MAC address
Wireless Access Point (WAP) — a device that allows wireless-capable devices to connect to a wired network using Wi-Fi, creating a wireless local area network
MAC address — a unique hardware identifier assigned to a network interface card by the manufacturer, consisting of 48 bits usually displayed as six pairs of hexadecimal digits
Packet switching — the method of breaking data into packets which are sent independently across a network and reassembled at the destination
Ethernet — the standard protocol for wired local area networks, defining how data is formatted and transmitted over network cables
Core concepts
Network interface cards (NICs)
A network interface card is essential hardware that enables any device to connect to a network. Every computer, laptop, tablet or smartphone contains at least one NIC, whether built into the motherboard or added as an expansion card.
Key features of NICs:
- Each NIC has a unique MAC address burned into its hardware during manufacture
- The MAC address consists of 48 bits, typically written as six pairs of hexadecimal digits (e.g., 00:1A:2B:3C:4D:5E)
- NICs can be wired (Ethernet port) or wireless (Wi-Fi adapter)
- Wired NICs use RJ-45 connectors to attach Ethernet cables
- Wireless NICs contain radio transceivers to send and receive data via electromagnetic waves
- The NIC handles the physical transmission of data between the device and the network
Modern devices often contain both wired and wireless NICs, allowing users to choose their connection method. Desktop computers may require a separate wireless NIC if one isn't built into the motherboard, while laptops typically have both types integrated.
The NIC operates at the physical and data link layers, converting digital data from the computer into signals suitable for transmission across the network medium, whether that's electrical signals through copper cables, light pulses through fibre optic cables, or radio waves through air.
Hubs
A hub is the most basic type of network connectivity device, now largely obsolete but still relevant for IGCSE examinations because it helps illustrate networking principles.
How hubs work:
- Connect multiple devices in a star topology network
- Receive data packets on one port
- Broadcast the same data to all other connected ports simultaneously
- Do not examine packet contents or destination addresses
- Operate at the physical layer only
- Create significant unnecessary network traffic
- All devices share the available bandwidth
The main disadvantage of hubs is inefficiency. When Device A sends data to Device B, the hub broadcasts this data to Devices C, D, E and all other connected devices. Each device must examine the packet to determine if it's the intended recipient, wasting processing power and creating security concerns since all devices can see all traffic.
Hubs also cause collisions when multiple devices transmit simultaneously. The network uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) to manage these collisions, reducing overall network performance.
Modern networks have almost entirely replaced hubs with switches due to these limitations.
Switches
A switch is an intelligent network device that connects multiple devices within a LAN, offering significant advantages over hubs.
How switches work:
- Connect multiple devices in a star topology network
- Maintain a MAC address table recording which devices are connected to which ports
- Examine the destination MAC address in each data packet header
- Forward packets only to the port connected to the intended recipient
- Operate at the data link layer
- Learn MAC addresses automatically by observing source addresses in incoming packets
- Provide full bandwidth to each port simultaneously
When a switch first powers on, its MAC address table is empty. As devices send data, the switch records each source MAC address and the port it came from. Over time, the switch builds a complete table of all connected devices.
When the switch receives a packet:
- It reads the destination MAC address from the packet header
- It checks its MAC address table to find which port connects to that MAC address
- It forwards the packet only to that specific port
- If the destination MAC address isn't in the table, the switch broadcasts to all ports (except the source port) and records the response
Advantages of switches over hubs:
- Reduced network congestion by eliminating unnecessary broadcasts
- Improved security as devices only receive data intended for them
- Better performance through simultaneous connections
- Fewer collisions due to intelligent traffic management
- More efficient use of bandwidth
Switches are the standard device for connecting computers, printers, servers and other devices within schools, offices and homes.
Routers
A router is a sophisticated network device that connects different networks together and routes data between them. Most commonly, routers connect a home or school LAN to the internet.
Key functions of routers:
- Forward data packets between different networks
- Use IP addresses to make routing decisions
- Maintain routing tables that map network destinations to optimal paths
- Assign local IP addresses to devices using DHCP (Dynamic Host Configuration Protocol)
- Provide Network Address Translation (NAT) to allow multiple devices to share one public IP address
- Include firewall capabilities to filter incoming and outgoing traffic
- Operate at the network layer
The router acts as a gateway between networks. In a typical home or school setup:
- Devices on the LAN have private IP addresses (e.g., 192.168.1.x)
- The router has a public IP address assigned by the Internet Service Provider (ISP)
- When a device requests data from the internet, the router translates the private IP to its public IP
- The router tracks which internal device made each request
- When responses arrive, the router forwards them to the correct internal device
Routers examine the destination IP address in each packet and consult their routing tables to determine the best path to that destination. For home routers, this is simple: packets for the local network stay local, while packets for external addresses are forwarded to the ISP.
Modern routers often combine multiple functions:
- Router functionality (connecting networks)
- Switch functionality (connecting multiple wired devices)
- Wireless access point (providing Wi-Fi)
- Modem (converting between digital and analogue signals for some connection types)
This combination device is sometimes called a "wireless router" or "home gateway."
Wireless access points (WAPs)
A wireless access point allows wireless-capable devices to connect to a wired network using Wi-Fi technology.
How WAPs work:
- Connect to a wired network via Ethernet cable
- Broadcast a wireless signal (SSID - Service Set Identifier) that devices can detect
- Use radio waves to transmit and receive data
- Encrypt wireless communications using protocols like WPA2 or WPA3
- Support multiple simultaneous wireless connections
- Extend the range of a network without requiring cables
WAPs create a wireless local area network (WLAN) that integrates with the existing wired LAN. Devices with wireless NICs can detect the WAP's broadcast and connect to it, gaining access to the wider network and potentially the internet.
Security considerations for WAPs:
- Must use encryption to prevent eavesdropping on wireless transmissions
- Require authentication (usually a password/passphrase) to prevent unauthorized access
- WPA3 (Wi-Fi Protected Access 3) is the current strongest encryption standard
- Older protocols like WEP (Wired Equivalent Privacy) are insecure and should not be used
- The SSID can be hidden to make the network less visible, though this isn't strong security
Many consumer devices marketed as "wireless routers" actually combine a router, switch, and WAP in one unit. A standalone WAP, however, doesn't route between networks or assign IP addresses—it simply provides wireless access to an existing wired network.
Wired vs wireless connections
Networks use either physical cables (wired) or radio waves (wireless) to transmit data. Each approach has distinct advantages and disadvantages.
Wired connections (Ethernet):
Advantages:
- Higher and more consistent data transfer speeds (typically 100 Mbps to 10 Gbps)
- More reliable connection with less interference
- More secure as physical access is required to intercept data
- No degradation from walls, distance or other obstructions
- Consistent latency, important for gaming and video conferencing
Disadvantages:
- Requires physical cables to be installed and maintained
- Less flexible—devices must remain connected to a cable
- Installation can be expensive and disruptive
- Limited by cable length and the number of ports available
- Cables can be tripping hazards or aesthetically unpleasing
Wireless connections (Wi-Fi):
Advantages:
- Mobility—devices can move freely within range
- Easy to add new devices without running cables
- Convenient for smartphones, tablets and laptops
- Less expensive installation for temporary setups
- Suitable for devices where cables are impractical
Disadvantages:
- Slower speeds than wired connections (typically 50-300 Mbps for consumer Wi-Fi)
- Signal strength decreases with distance and physical obstructions
- Susceptible to interference from other wireless devices and electromagnetic sources
- Less secure unless properly encrypted
- Shared bandwidth reduces speed when many devices connect simultaneously
- Higher latency and potential for packet loss
In practice, most modern networks use a combination: wired connections for stationary devices requiring high performance (desktop computers, servers, printers) and wireless connections for mobile devices and convenience.
Worked examples
Example 1: Identifying appropriate network hardware
Question: A school is setting up a new computer laboratory with 30 desktop computers that will connect to the internet. All computers will be in fixed positions.
(a) State which device should be used to connect all 30 computers together in the laboratory. [1]
(b) Explain why this device is more suitable than a hub for this purpose. [2]
(c) Identify the hardware component each computer requires to connect to the network. [1]
(d) State which device is needed to connect the laboratory network to the internet. [1]
Mark scheme answers:
(a) Switch [1 mark]
(b)
- A switch forwards data only to the intended recipient // reduces network traffic [1 mark]
- A hub broadcasts to all devices // causing unnecessary traffic and reducing performance [1 mark]
Alternative acceptable answers:
- A switch is more secure as only the intended device receives data
- A switch provides better bandwidth utilization
- A switch prevents collisions by managing traffic intelligently
(c) Network Interface Card // NIC // Ethernet card // network adapter [1 mark]
(d) Router [1 mark]
Example 2: MAC addresses and switches
Question: A switch connects four computers in a small office network. The MAC addresses and assigned switch ports are:
- Computer A: 00:1A:2B:3C:4D:5E (Port 1)
- Computer B: 00:1A:2B:3C:4D:5F (Port 2)
- Computer C: 00:1A:2B:3C:4D:60 (Port 3)
- Computer D: 00:1A:2B:3C:4D:61 (Port 4)
Computer A sends a packet addressed to MAC address 00:1A:2B:3C:4D:60.
(a) Identify which computer will receive this packet. [1]
(b) Describe how the switch uses the MAC address to forward this packet. [3]
Mark scheme answers:
(a) Computer C [1 mark]
(b)
- The switch reads the destination MAC address (00:1A:2B:3C:4D:60) from the packet header [1 mark]
- The switch checks its MAC address table to find which port this address is associated with [1 mark]
- The switch forwards the packet only to Port 3 // the switch does not send the packet to Ports 2 or 4 [1 mark]
Example 3: Wired vs wireless comparison
Question: A business is deciding between installing wired Ethernet cables or using a wireless network for their office.
(a) Give two advantages of using a wired network instead of wireless. [2]
(b) Give one disadvantage of using a wired network. [1]
(c) State which device would be required to provide wireless connectivity to the existing wired network. [1]
Mark scheme answers:
(a) Any two from:
- Faster // more consistent data transfer speeds [1 mark]
- More secure // harder to intercept data [1 mark]
- More reliable connection // less interference [1 mark]
- Better for fixed desktop computers that don't need to move [1 mark]
(b) Any one from:
- Expensive // time-consuming to install cables [1 mark]
- Less flexible // devices cannot move freely [1 mark]
- Requires physical cable connections for each device [1 mark]
- Cables may be unsightly // trip hazards [1 mark]
(c) Wireless Access Point // WAP // Wi-Fi access point [1 mark]
Common mistakes and how to avoid them
Confusing switches and routers: Remember that switches connect devices within the same network (LAN), while routers connect different networks together. Switches use MAC addresses; routers use IP addresses.
Saying hubs are "better" or "modern": Hubs are outdated technology. Always explain their disadvantages (broadcasting to all devices, wasting bandwidth, security concerns) when comparing them to switches.
Forgetting that NICs have MAC addresses: Many students describe NICs but forget to mention that each has a unique MAC address burned into it. This is essential for network communication and frequently examined.
Confusing WAPs with routers: A wireless access point only provides wireless connectivity to an existing wired network. It doesn't route between networks or assign IP addresses unless these functions are combined in a single device.
Being vague about wired/wireless advantages: Instead of saying "wired is faster," quantify when possible ("wired connections typically provide 1 Gbps while wireless provides 50-300 Mbps") and be specific about which scenarios favour each type.
Not explaining how devices use MAC addresses: When describing switches, explain the process: reading the destination MAC address, checking the table, forwarding to the correct port. Don't just say "switches use MAC addresses."
Exam technique for "The internet and networking: hardware used in networks (router, switch, hub, NIC, WAP) and wired/wireless connections"
Command word awareness: "State" or "Identify" questions (1 mark) require brief answers—just the name of the device. "Describe" (2-3 marks) requires a process or sequence of steps. "Explain" (2-3 marks) requires reasons or causes—use "because," "therefore," or "so that" to link points.
Comparison questions require both sides: When asked to compare hubs and switches, or wired and wireless connections, always discuss both options. If asked for advantages of wired, implicitly mention wireless disadvantages and vice versa.
Use technical terminology precisely: The examiner looks for specific terms like "MAC address table," "destination address," "broadcast," "packet," and "bandwidth." Vague language like "sends information" loses marks compared to "forwards data packets."
Context matters: If a question describes a scenario (school laboratory, business office, home network), tailor your answer to that context. A desktop computer in a laboratory should use wired; a tablet needs wireless. Justify recommendations based on the specific requirements given.
Quick revision summary
Network hardware includes NICs (with unique MAC addresses enabling network connection), hubs (outdated devices broadcasting to all ports), switches (intelligent devices forwarding packets only to intended recipients using MAC address tables), routers (connecting different networks using IP addresses and providing internet access), and WAPs (enabling wireless devices to connect to wired networks). Wired connections offer superior speed, reliability and security but lack flexibility, while wireless connections provide mobility and convenience with reduced performance and potential interference. Switches have replaced hubs in modern networks due to efficiency and security advantages.