Cambridge A-Level Computer Science 9618 – 2.1 Networks (Internet Hardware)2.1 Networks – The Internet
Objective
Describe the hardware that is used to support the internet.
Key Hardware Components
- Routers – Direct data packets between different networks; operate at Layer 3 (Network layer).
- Switches – Connect multiple devices within a local area network (LAN); operate at Layer 2 (Data Link layer).
- Modems – Modulate and demodulate signals for transmission over telephone lines, cable, DSL, or fiber.
- Network Interface Cards (NICs) – Provide physical and data‑link connectivity for end‑devices.
- Servers – Host web pages, email, DNS, and other services; typically housed in data centres.
- Data Centre Infrastructure
- Racks and blade enclosures
- Power distribution units (PDUs)
- Cooling systems (CRAC units, liquid cooling)
- Uninterruptible power supplies (UPS) and generators
- Firewalls (Hardware) – Inspect and filter traffic at network perimeters.
- Load Balancers – Distribute incoming traffic across multiple servers to improve performance and reliability.
- Repeaters & Amplifiers – Regenerate weakened signals over long distances, especially in fiber‑optic links.
- Wireless Access Points (WAPs) – Provide Wi‑Fi connectivity for mobile devices.
- Satellite Dishes & Ground Stations – Enable broadband access in remote locations via geostationary or low‑Earth‑orbit satellites.
- Cabling
- Fiber‑optic cables (single‑mode, multimode) – High bandwidth, low attenuation.
- Twisted‑pair copper (Cat 5e, Cat 6, Cat 6a, Cat 7) – Common for Ethernet.
- Coaxial cable – Used in cable broadband and some legacy networks.
Hardware Functions in the Internet Architecture
| Hardware | Primary Function | Typical Deployment Location |
|---|
| Router | Path selection and packet forwarding between autonomous systems | Internet Service Provider (ISP) backbone, enterprise edge |
| Switch | Frame forwarding within a LAN based on MAC addresses | Office floors, data‑centre racks |
| Modem | Conversion between digital data and analog signals for transmission over a specific medium | Customer premises, ISP central office |
| NIC | Physical connection of a device to a network medium | Desktop computers, laptops, servers |
| Server | Provision of services such as web, email, DNS, cloud storage | Data centres, colocation facilities |
| Firewall (hardware) | Inspection and enforcement of security policies at network borders | Enterprise perimeter, ISP edge |
| Load Balancer | Distribute client requests across multiple servers to optimise resource use | Data centre front‑end, cloud platforms |
| Repeater / Amplifier | Boost signal strength to extend transmission distance | Long‑haul fiber routes, submarine cable landing stations |
| Wireless Access Point | Provide wireless connectivity using IEEE 802.11 standards | Office buildings, public hotspots |
| Satellite Dish | Transmit and receive data to/from orbiting satellites | Rural homes, maritime vessels, remote research stations |
| Fiber‑optic Cable | Carry light‑based signals with very high bandwidth and low loss | Backbone networks, inter‑city links, undersea cables |
Typical Internet Hardware Path (Client to Server)
- Client device with a NIC connects to a Wi‑Fi Access Point or Ethernet switch.
- Switch forwards frames to the router at the ISP edge.
- Router uses routing tables to forward packets onto the ISP’s backbone.
- Backbone routers forward the packets across fiber‑optic links (possibly through repeaters/amplifiers).
- At the destination data centre, a load balancer distributes the request to an appropriate web server.
- Response follows the reverse path, traversing the same hardware components back to the client.
Supporting Infrastructure
Beyond the primary devices, the internet relies on a range of supporting hardware to maintain reliability, performance, and security:
- Power backup systems (UPS, diesel generators) to prevent outages.
- Environmental controls (H \cdot AC, liquid cooling) to keep equipment within operating temperatures.
- Monitoring appliances (SNMP probes, network taps) for traffic analysis and fault detection.
- Physical security devices (cameras, access control) to protect data‑centre assets.
Suggested diagram: Layered view of internet hardware from end‑user devices through access networks, ISP backbone, and data‑centre infrastructure.