Show understanding of the purpose and benefits of networking devices

2.1 Networks – Purpose and Benefits of Networking Devices

Learning objective

Show understanding of the purpose and benefits of networking devices and how they support different network types, topologies and services required by the Cambridge AS & A‑Level Computer Science syllabus (Topic 2.1).

Syllabus coverage at a glance

Why use networking devices?

• Physical connectivity – provide the medium (copper, fibre, radio) that links devices.
• Logical separation of traffic – VLANs, sub‑nets, and bridges keep different kinds of data apart.
• Control of data flow – error handling, collision avoidance, QoS, and security policies.
• Scalability – new hosts or sites can be added without redesigning the whole network.

Network types – LAN vs WAN

Client‑Server vs Peer‑to‑Peer (P2P) models

• Client‑Server – Centralised servers host services; clients request resources.
  • Typical services: web, email, file sharing, database.
  • Exam‑style scenario: A school runs an intranet web server that stores the timetable. All student PCs (clients) retrieve the page via HTTP.
• Peer‑to‑Peer (P2P) – Every node can act as both client and server; resources are shared directly.
  • Typical use: file‑sharing, collaborative editing, distributed computing.
  • Exam‑style scenario: Two laptops in a computer club exchange a large video file using BitTorrent without involving a central server.

Thin‑client vs Thick‑client

• Thin client – Minimal local processing; the operating system and applications run on a remote server (often via Virtual Desktop Infrastructure – VDI).
  • Benefits: easier maintenance, lower hardware cost, data centralisation.
  • Example: Classroom PCs boot a Windows 10 VDI session from a central server.
• Thick client – Most processing and storage occur locally on the device.
  • Benefits: works when the network is down, can run resource‑intensive software.
  • Example: A teacher’s laptop running Microsoft Office and a video‑editing suite.

Network topologies

Wired vs wireless networks

Cloud computing & networking

When services are hosted in the cloud (IaaS, PaaS, SaaS) the on‑premises network must be able to:

• Provide secure VPN tunnels for remote staff.
• Segregate traffic with VLANs or virtual routing (e.g., separate production and management traffic).
• Scale bandwidth on demand to cope with bursty cloud traffic.

Hardware that supports a LAN

1. Network Interface Card (NIC) – Physical & data‑link interface on a host (Layer 1‑2). Enables a device to join a network.
2. Hub – Repeats incoming electrical signals to all ports (Layer 1). Simple, low‑cost, but causes collisions.
3. Switch – Forwards Ethernet frames to the correct destination MAC address (Layer 2). Reduces collisions and improves bandwidth utilisation.
4. Bridge – Connects two LAN segments and filters traffic using MAC addresses (Layer 2). Provides segmentation without full routing.
5. Router – Routes IP packets between different networks (Layer 3). Performs NAT, DHCP relay and can implement ACLs.
6. Gateway – Converts between different protocols or architectures (e.g., IPv4 ↔ IPv6, Ethernet ↔ Wi‑Fi). May involve several OSI layers.
7. Modem – Modulates/demodulates signals for transmission over analog media (telephone, cable) (Layer 1). Connects the LAN to an ISP.
8. Access Point (AP) – Provides wireless connectivity to a wired LAN (Layer 2/3). Handles association, authentication and radio management.
9. Firewall – Enforces security policies by filtering traffic (Layer 3‑7). Can perform stateful inspection, intrusion detection and VPN termination.

Device‑specific benefits (quick reference)

IP addressing overview

• IPv4 – 32‑bit address (e.g., 192.168.1.10). Approximately 4.3 billion unique addresses.
• IPv6 – 128‑bit address (e.g., 2001:0db8:85a3::8a2e:0370:7334). Provides an effectively unlimited address space.
• Subnetting – Divides a network into smaller logical segments using a subnet mask (e.g., /24 = 255.255.255.0). Improves security and reduces broadcast traffic.
• Public vs private addresses – Public addresses are routable on the Internet; private ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) are used internally and require NAT for Internet access.
• Static vs dynamic allocation – Static addresses are manually configured; dynamic addresses are assigned by a DHCP server.

URL resolution and DNS

When a user enters https://www.example.com/index.html the following steps occur:

1. The browser extracts the domain name www.example.com.
2. A DNS query is sent to a resolver, which returns the corresponding IP address (e.g., 93.184.216.34).
3. The browser opens a TCP connection to that IP address on port 443 and requests /index.html.

Bit‑streaming concepts

• Real‑time streaming – Data is consumed as it arrives (e.g., live video conference). Requires steady bandwidth and low latency.
• On‑demand streaming – Content is buffered before playback (e.g., Netflix). Allows variable bandwidth but still benefits from high throughput.

Security implications of networking devices

• Firewalls – Block unauthorised inbound/outbound traffic; can perform stateful inspection and application‑layer filtering.
• VPN routers – Encrypt traffic for secure remote access over public networks.
• Switch security – MAC address filtering, VLAN segregation, and port security prevent unauthorised devices from connecting.
• Wireless security – Use WPA3 encryption, hide SSID where appropriate, and optionally enable MAC‑address filtering.

Performance metric example

Network throughput is calculated as:

$$\text{Throughput} = \frac{\text{Total bits transferred}}{\text{Transfer time}}$$

Using a switch that isolates frames by MAC address reduces collisions, so more bits are successfully transferred in the same time interval, increasing throughput.

Suggested diagram

Summary

Networking devices are the building blocks that make modern computer networks possible. They provide the physical links, logical segregation, traffic control, security and scalability required for LANs, WANs and cloud‑based services. Understanding each device’s purpose, the OSI layer it operates in, and the benefits it brings equips students to design, evaluate and troubleshoot real‑world network solutions in line with the Cambridge AS & A‑Level syllabus.