16.1 Network Types and Wired and Wireless Communication
Key Takeaways
- Networks by scale: PAN (a few meters, such as Bluetooth), LAN (a building or campus), MAN (a city), and WAN (regions or countries); the Internet is the largest WAN.
- Fiber-optic cable carries data as light, so it supports very high bandwidth over long distances and is immune to electromagnetic interference; twisted-pair copper is cheaper and standard for connecting devices within buildings.
- Category 5e twisted pair supports 1 Gbps and Category 6a supports 10 Gbps, each up to 100 meters per cable run.
- Wireless systems trade range for speed and power: NFC works within centimeters, Bluetooth about 10 meters, Wi-Fi a building, and cellular and satellite much larger areas.
- In a star topology every device connects to a central switch, so one cable failure affects only one device, but the switch is a single point of failure; a mesh has redundant paths.
What this competency asks
ETS asks you to be familiar with communication between devices:
- Identify and compare wireless communication systems.
- Identify and compare wired communication systems.
- Identify and compare network types.
Network types by scale
| Type | Scale | Typical technology | Example |
|---|---|---|---|
| PAN (personal area network) | A few meters around one person | Bluetooth, USB, NFC | Phone connected to earbuds and a watch |
| LAN (local area network) | A room, building, or campus | Ethernet, Wi-Fi | A school's computer labs and classrooms |
| WLAN (wireless LAN) | Same as a LAN | Wi-Fi access points | Classroom Wi-Fi |
| MAN (metropolitan area network) | A city | Fiber rings, fixed wireless | Linking a district's schools across town |
| WAN (wide area network) | Regions, countries, continents | Leased fiber lines, undersea cables, satellite | A company linking offices in several states |
| The Internet | Global | A network of networks | Everything connected worldwide |
LANs are usually owned and managed by one organization and are fast. WANs often use carriers' infrastructure, cover distance, and cost more per unit of bandwidth.
Other ways to classify networks
- Client–server: dedicated servers provide services (websites, files, email) to client devices. This model is centrally managed and secured, but the server can become a bottleneck or single point of failure.
- Peer-to-peer (P2P): devices share resources directly as equals, as in some file-sharing systems. There is no central server to fail, but it is harder to manage and secure.
Topologies
| Topology | Layout | Strengths | Weaknesses |
|---|---|---|---|
| Star | Every device connects to a central switch | Easy to add devices; one cable failure affects only one device | The central switch is a single point of failure |
| Bus | All devices share one backbone cable | Little cable | One break disables the network; collisions; obsolete |
| Ring | Each device connects to two neighbors in a loop | Orderly access | One break can stop a simple ring |
| Mesh | Devices have multiple paths to one another | Highly fault tolerant; traffic reroutes around failures | Costly; a full mesh of n nodes needs n(n − 1)/2 links |
Most modern LANs are physically star networks built with switches. The Internet's core is a partial mesh, which is why it can route around failures.
Wired communication
| Medium | How it carries data | Speed and distance | Strengths | Weaknesses |
|---|---|---|---|---|
| Twisted-pair copper (Ethernet: Cat 5e, 6, 6a) | Electrical signals on twisted wire pairs | Cat 5e: 1 Gbps; Cat 6a: 10 Gbps; 100 m per run | Cheap, easy to install; standard in buildings | Distance limit; affected by electrical interference |
| Coaxial cable | Electrical signals on a shielded central wire | High bandwidth over moderate distances | Good shielding; used for cable Internet and TV | Bulkier; being replaced by fiber |
| Fiber optic | Pulses of light in glass fibers | Very high bandwidth; kilometers without boosting (single-mode) | Immune to electromagnetic interference; hard to tap; long distance | More expensive to install and terminate |
Twisting the copper pairs reduces crosstalk and interference. Fiber's resistance to electromagnetic interference makes it the choice for building backbones, between buildings, and for undersea cables.
Wired vs. wireless in general: wired links are usually faster, more reliable, more secure, and lower in latency. Wireless links offer mobility and are easier to deploy.
Wireless communication
| System | Typical range | Typical use | Notes |
|---|---|---|---|
| NFC (near-field communication) | A few centimeters | Tap-to-pay, transit cards, badge readers | The short range is a security feature |
| Bluetooth | About 10 m (varies) | PANs: headphones, keyboards, wearables | Low power; modest data rates |
| Wi-Fi (IEEE 802.11) | Tens of meters indoors | WLANs in homes and schools | 2.4 GHz reaches farther and passes walls better but is crowded; 5 and 6 GHz are faster at shorter range |
| Zigbee and similar | Tens of meters, mesh | Smart-home sensors | Very low power (Section 15.3) |
| Cellular (4G LTE, 5G) | Kilometers per tower | Phones, mobile hotspots | Wide coverage; data plans; 5G adds speed and lower latency |
| Satellite | Nearly global | Rural and remote Internet, ships, aircraft | Geostationary satellites add high latency; low-Earth-orbit systems reduce it |
| Infrared | Line of sight, short | TV remotes | Blocked by walls |
Trade-offs across wireless systems: longer range generally means more power or infrastructure. Higher frequencies carry more data but travel less far and are blocked more easily. Every wireless signal can be intercepted, so it must be encrypted (WPA3 for Wi-Fi). Interference and congestion reduce real-world speeds below advertised maximums.
Choosing a connection
| Need | Best choice |
|---|---|
| Connect two buildings 500 m apart at high speed | Fiber optic |
| Desktop computers in a lab, reliably | Twisted-pair Ethernet |
| Laptops moving between classrooms | Wi-Fi |
| Wireless headphones | Bluetooth |
| Contactless payment | NFC |
| Internet at a remote research station | Satellite |
A district needs a high-speed link between two school buildings 2 kilometers apart, passing near heavy electrical equipment. Which medium is most appropriate?
A student's phone connects wirelessly to a smartwatch and earbuds within a meter or two of the student's body. What type of network is this?
Which wireless technology is designed to work only within a few centimeters, which makes it suitable for tap-to-pay transactions?
In a star-topology LAN, one computer's network cable is cut. What is the expected effect?