Show understanding of the differences between and implications of the use of wireless and wired networks

2.1 Networks – The Internet

Objective

Show understanding of the differences between, and the implications of, the use of wireless and wired networks.

1. Basic Networking Terminology (Glossary)

2. Core Network Hardware

• Network Interface Card (NIC) – provides the physical & data‑link connection to a network (wired or wireless).
• Hub – a multi‑port repeater; repeats incoming electrical signals to all ports (obsolete, replaced by switches).
• Switch – learns MAC addresses and forwards frames only to the appropriate port (layer‑2 device).
• Bridge – connects two LAN segments and filters traffic based on MAC addresses (functionally similar to a simple switch).
• Router – operates at layer‑3, forwards packets between different IP networks, performs NAT and routing.
• Repeater – regenerates and amplifies signals to extend the maximum cable length.

3. LAN vs WAN

4. LAN Topologies & Typical Media

5. Physical Media

• Wired: Twisted‑pair copper (Cat 5e/6/6a), coaxial cable, fibre‑optic cable.
• Wireless: Radio‑frequency (RF) electromagnetic waves – microwave, millimetre‑wave, and infrared.

6. Transmission Characteristics

• Bandwidth (throughput) – maximum number of bits transferred per second.
• Latency – total time for a bit to travel from source to destination (propagation + serialization + processing + queuing).
• Attenuation – loss of signal strength with distance or obstacles.
• Interference – unwanted RF signals that corrupt a transmission; far more common in wireless links.

7. Standards, Protocols & OSI/TCP‑IP Mapping

Only the most relevant protocols for the Cambridge syllabus are listed.

8. MAC‑Layer Access Methods

• CSMA/CD (Carrier‑Sense Multiple Access with Collision Detection) – used by wired Ethernet. Devices listen, transmit, and if a collision is detected they back‑off and retry.
• CSMA/CA (Carrier‑Sense Multiple Access with Collision Avoidance) – used by Wi‑Fi. Devices listen, wait a random back‑off, and use acknowledgements to confirm successful receipt, reducing the chance of collisions.

9. Client‑Server, Peer‑to‑Peer & Thin/Thick Clients

• Client‑Server model – a central server provides resources/services (e.g., a web server delivering pages to browsers). Advantages: control, security, easy backup.
• Peer‑to‑Peer (P2P) model – each node can act as both client and server (e.g., BitTorrent). Advantages: distributed load, resilience; disadvantages: less control.
• Thin client – minimal processing locally; most work is performed on a server (e.g., a web‑based office suite).
• Thick (fat) client – substantial processing and storage on the local machine (e.g., a desktop IDE).

10. Bit‑Streaming Concepts

Two main ways of delivering media over a network:

• Real‑time (live) streaming – data is sent as it is produced; low latency is critical (e.g., video‑conference, live sport). Often uses UDP with RTP.
• On‑demand (download) streaming – data is stored on a server and retrieved when requested; buffering hides network jitter (e.g., YouTube, Netflix).

11. Security Considerations

• Wired networks

  • Physical security – an attacker must gain physical access to cables or switch ports.
  • Link‑layer encryption rarely required; confidentiality is usually provided by higher‑layer protocols (TLS/SSL, VPN).

• Wireless networks

  • Link‑layer encryption – WPA3 (IEEE 802.11i) provides AES‑CCMP encryption and robust authentication.
  • Network‑layer security – TLS/SSL for web traffic, IPsec or VPN for remote access.
  • Additional controls – MAC‑address filtering, rogue‑AP detection, regular key rotation, 802.11w management‑frame protection.

12. Cost, Scalability, Installation & Maintenance

• Initial deployment

  • Wired – cabling, conduit, patch panels, and skilled labour are expensive, especially in retrofit projects.
  • Wireless – lower upfront cost; main expense is access points (APs) and site‑survey tools.

• Scalability

  • Wired – limited by port density, cable‑run length (100 m for copper), and backbone capacity.
  • Wireless – adding APs expands coverage, but spectrum availability and channel reuse impose limits.

• Maintenance

  • Wired – physical faults are easy to locate; performance is stable once installed.
  • Wireless – requires firmware updates, periodic spectrum analysis, and optimisation of channel allocation.

13. Protocol‑Level Implications

• Ethernet frame – preamble, destination MAC, source MAC, EtherType, payload, CRC.
• Wi‑Fi frame – Frame Control, Duration/ID, address fields, Sequence Control, payload, FCS; includes management and control sub‑frames.
• Both rely on ARP to map IP addresses to MAC addresses within a LAN.

14. IP Addressing, DNS & Cloud‑Computing Context

• IP addressing

  • IPv4 – e.g., 192.168.0.0/24 (private) or 203.0.113.0/24 (public).
  • IPv6 – e.g., 2001:db8::/32 (documentation prefix) or provider‑assigned global prefix.
  • Subnetting determines the number of hosts per LAN; CIDR notation is used for both IPv4 and IPv6.

• DNS – translates human‑readable domain names to IP addresses; typically queried via UDP 53 (TCP 53 for large responses or zone transfers).
• Cloud implications

  • Public‑cloud services are accessed over the Internet; the edge connection (wired or wireless) directly influences latency and bandwidth.
  • Hybrid or private clouds often use dedicated fibre links (e.g., MPLS or Direct Connect) for high‑speed, low‑latency connectivity.

15. Wireless‑Specific Issues

• Interference sources – neighbouring Wi‑Fi networks, Bluetooth, microwave ovens, cordless phones, and other 2.4 GHz/5 GHz devices.
• Spectrum & channel planning – 2.4 GHz offers 3 non‑overlapping 20 MHz channels; 5 GHz offers up to 24; 6 GHz (Wi‑Fi 6E) adds many more. Proper channel allocation reduces co‑channel interference.
• Hand‑off / roaming – mobile devices move between APs; seamless hand‑off requires a common SSID, overlapping coverage, and fast re‑authentication (e.g., 802.11r).
• Signal attenuation – walls, glass, metal, and furniture absorb RF energy; site surveys and optimal AP placement (height, antenna orientation) mitigate loss.

16. Comparison of Wired and Wireless Networks

17. Implications for Network Design

1. Performance requirements – latency‑sensitive services (online gaming, high‑frequency trading, real‑time control) should use wired links; bulk data transfer and mobile access can tolerate wireless.
2. Physical environment – historic or heritage buildings may prohibit cabling; wireless provides a practical alternative but demands careful planning for attenuation and interference.
3. Security policy – combine physical security for wired segments with strong WPA3, regular key rotation, and intrusion‑detection for wireless.
4. Cost considerations – evaluate total cost of ownership: cabling labour vs. ongoing wireless spectrum management and AP replacement cycles.
5. Future‑proofing – deploy fibre backbones for unlimited bandwidth growth; choose APs that support the latest Wi‑Fi standards (6E/7) for incremental upgrades.
6. IP & DNS planning – allocate appropriate IPv4/IPv6 subnets, reserve address space for IoT devices, and ensure DNS servers are reachable over both wired and wireless paths.
7. Cloud connectivity – for hybrid cloud architectures, provision dedicated fibre or high‑capacity Wi‑Fi links to the edge router to meet SLA requirements.

18. Mathematical Modelling of Transmission Time

The total time T for a packet of size S bits to travel across a link is:

\[

T = \frac{S}{B} + D + P + Q

\]

• S / B – transmission (serialization) delay.
• D – propagation delay (distance ÷ signal speed).
• P – processing delay at each node.
• Q – queuing delay caused by congestion.

Example – wired Ethernet (1 Gbps, 0.5 ms propagation, negligible P and Q):

\[

T_{\text{wired}} = \frac{12\,000}{10^{9}} + 0.5\times10^{-3} \approx 0.500012\ \text{ms}

\]

Example – Wi‑Fi (802.11ax) (300 Mbps, 10 ms propagation, P ≈ 1 ms, Q ≈ 2 ms):

\[

T_{\text{wireless}} = \frac{12\,000}{3\times10^{8}} + 10\times10^{-3} + 1\times10^{-3} + 2\times10^{-3}

\approx 13.00004\ \text{ms}

\]

This demonstrates why wired links are preferred for latency‑critical applications.

19. Suggested Diagram

20. Summary

Wired and wireless networks each have distinct advantages and limitations. A well‑designed solution balances performance, security, cost, scalability and future growth. Understanding quantitative differences (bandwidth, latency, attenuation) together with protocol‑level details (CSMA/CD, CSMA/CA, Ethernet framing, Wi‑Fi standards) enables students to decide when to deploy each technology, how to integrate them, and how they fit into the broader IP‑based Internet architecture.