Network Hardware and Topologies

Network Hardware and Topologies

A computer network is two or more devices connected together to share data and resources. This note covers the hardware needed to build networks and the topologies (layouts) used to connect devices.

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Types of Network

Type	Description	Range	Example
LAN (Local Area Network)	Covers a small geographical area	Single building/site	School network
WAN (Wide Area Network)	Covers a large geographical area	Cities/countries	The Internet

Key Differences

Feature	LAN	WAN
Size	Small (one site)	Large (multiple sites)
Ownership	Owned by one organisation	Uses third-party infrastructure
Speed	Generally faster	Generally slower
Hardware	Switches, access points	Routers, leased lines

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Network Hardware

Network Interface Card (NIC)

• Hardware inside every networked device
• Has a unique MAC address (burned into the hardware)
• Converts data into signals for transmission
• Can be wired (Ethernet) or wireless (Wi-Fi)

Switch

• Connects devices within a LAN
• Receives data and forwards it only to the intended recipient using MAC addresses
• More efficient than a hub (which sends data to all ports)
• Operates at the data link layer

Router

• Connects different networks together (e.g. your LAN to the Internet)
• Uses IP addresses to direct (route) data packets to their destination
• Chooses the best path for data to travel
• Operates at the network layer

Wireless Access Point (WAP)

• Allows wireless devices to connect to a wired network
• Broadcasts a Wi-Fi signal
• Acts as a bridge between wireless and wired parts of the network

Modem

• Converts digital data from a computer into analogue signals for transmission over telephone lines (and vice versa)
• Often built into the router in home networks ("router" is often actually a modem-router)

Transmission Media

Medium	Type	Speed	Distance	Cost
Ethernet cable (Cat5e/6)	Wired	Up to 10 Gbps	~100m	Low
Fibre optic	Wired	Up to 100+ Gbps	Many km	High
Wi-Fi	Wireless	Up to ~1 Gbps	~50m indoors	Medium

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Network Topologies

A topology is the arrangement of devices and connections in a network. The three you need to know are star, mesh, and bus.

Star Topology

All devices connect to a central switch or hub.

Advantages:

• If one cable fails, only that device is affected — the rest of the network continues working
• Easy to add new devices without disrupting the network
• Faults are easy to isolate and fix
• Better performance — no data collisions (with a switch)

Disadvantages:

• If the central switch fails, the entire network goes down
• Requires more cabling than bus (each device needs its own cable)
• More expensive due to the switch and extra cables

Mesh Topology

Every device connects to every other device (full mesh) or to several others (partial mesh).

Advantages:

• No single point of failure — if one connection breaks, data can take an alternative route
• Very reliable and robust
• Data can be transmitted from multiple devices simultaneously
• Fast communication — data takes the shortest available path

Disadvantages:

• Very expensive — lots of cabling and network ports needed
• Complex to set up and manage
• Full mesh is impractical for large networks (too many connections)
• Maintenance is difficult due to the number of connections

Bus Topology

All devices connect to a single central cable (the backbone or bus). Terminators are placed at each end to prevent signal reflection.

Advantages:

• Cheap to set up — uses less cabling
• Simple to install for small networks
• Easy to extend by adding devices to the backbone

Disadvantages:

• If the backbone cable fails, the entire network goes down
• Performance degrades as more devices are added (more collisions)
• Data is sent to all devices — security risk and slower
• Difficult to isolate faults
• Limited cable length and number of devices

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Topology Comparison

Feature	Star	Mesh	Bus
Cost	Medium	High	Low
Reliability	Medium	High	Low
Performance	Good	Excellent	Poor (many devices)
Single point of failure	Central switch	None	Backbone cable
Scalability	Easy	Complex	Limited
Best for	Most LANs	Critical systems	Small/temporary networks

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Client-Server vs Peer-to-Peer

Feature	Client-Server	Peer-to-Peer (P2P)
Central server	Yes — manages resources	No — all devices are equal
Security	Centralised, strong	Each device manages its own
Backups	Centralised	Each user responsible
Cost	Higher (server hardware)	Lower
Scalability	Good	Poor
Example	School network	Home file sharing

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Exam Tips

• Draw and label topologies clearly in diagram questions
• Always discuss advantages AND disadvantages — a comparison question needs both sides
• Remember: star has a single point of failure at the switch, bus at the backbone cable, mesh has no single point of failure
• Know the difference between a switch (uses MAC addresses, same network) and a router (uses IP addresses, connects different networks)
• The Internet is a WAN that uses a mesh topology