08 Network foundations, hardware and architectures

Network foundations, hardware and architectures

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Priority key · Priorities guide emphasis; they do not remove taught scope.

Exam recall

Switch: frames/MAC within a LAN. Router: packets/IP between networks. Recommend architecture/media by linking a feature to a scenario need.

Why connect computers? priority/medium

A network connects devices so that they can exchange data and share resources/services. Benefits include shared files and printers, communication, central administration and shared Internet access. Costs include equipment and management, dependence on network availability, and more routes through which unauthorised access or malware may spread. Explain how a benefit helps the scenario rather than writing only “resource sharing”.

A LAN covers a limited local area, commonly under one organisation’s administration. A WAN spans a wider geographical area and can link LANs using telecommunications services. The Internet is a network of networks; the Web is one service using it, not a synonym.

Hardware: function before name priority/high

Follow one message to understand the devices. A desktop’s NIC provides its connection. A switch delivers frames within its LAN. A router is needed when the IP destination is on another network. A wireless access point lets a wireless client join the network; it does not replace the need to route between IP networks.

flowchart LR
    A[Classroom desktop and NIC] --- S[LAN switch]
    B[Classroom printer] --- S
    W[Wireless laptop] --- P[Access point]
    P --- S
    S --- R[Router]
    R --- L[Library IP network]

Choose the device by the boundary the message crosses and the forwarding decision required. A box’s marketing label is less useful than its function.

Device	Essential function
NIC	Provides a device’s network interface, supporting the link and its addressing.
Switch	Connects devices within a LAN and forwards frames using learned destination MAC information.
Router	Connects IP networks and chooses a next hop for packets using a routing table.
Wireless access point	Connects wireless clients to a network, commonly bridging them to a wired LAN.
Modem	Converts signals as required for a particular access link; not interchangeable with “router”.
Hub	Repeats received signals to other ports without a switch’s selective forwarding.

A consumer “router” box may combine several functions. In an exam asking for a device’s role, describe the particular role rather than treating them as identical.

Client–server versus peer-to-peer priority/high

In client–server architecture, clients request services from servers. Central control can simplify access management and backups; specialised servers can serve many clients. Server failure or overload can affect dependent clients, and administration costs may be greater.

In peer-to-peer architecture, peers can both request and provide resources. It can suit small, simple sharing arrangements without a dedicated server. Decentralised administration and backup can be harder; a resource may be unavailable when its owner is offline. A peer-to-peer architecture does not imply that every device is connected by a direct physical cable to every other device.

Physical topology describes physical links; logical architecture describes roles and communication. In a star, each endpoint connects to a central device: one endpoint cable failure usually isolates that endpoint, while central-device failure affects the star. Mesh provides multiple possible paths but requires more connections and management. Bus uses a shared backbone; ring links nodes in a loop. Reliability depends on the actual design, including redundancy.

An intranet is an organisation’s private internal network/service environment using Internet technologies. A communication system needs a sender, receiver, message, medium and protocol; the protocol supplies agreed rules for message format and exchange. A repeater regenerates signals to extend a link’s reach without making IP routing decisions.

Simplex sends in one direction only; half-duplex allows both directions but one at a time; full-duplex allows both simultaneously. These describe transmission direction, not whether the network is LAN or WAN.

Transmission media priority/medium

Twisted-pair copper is common and comparatively inexpensive for short LAN links but is subject to distance and interference constraints. Fibre carries light, supports high capacity over long distances and resists electromagnetic interference, but installation/equipment can cost more. Wireless provides mobility and avoids endpoint cables, with variable range, interference and shared-medium/security considerations. Select based on distance, capacity, environment, mobility and cost.

Worked example — original

A school needs students to access centrally controlled lesson files from classroom desktops. Client–server fits because a server can enforce permissions and maintain a central copy/backup. A switch connects desktops within a classroom LAN; a router connects that LAN to other IP networks. Wireless access points are useful for roaming laptops, but are not required just because the files are shared.

Practice

Exam focus: HCI 2024 Q1 compares switch/router functions; HCI 2025 Q2 asks for networking benefits. The 2022 modified Q4 and ASRJC 2025 Q3 include network/application architecture. These require explanations connected to the scenario, not a list of device names.

Answering approach for “recommend”: requirement → choice → how the choice meets it → a relevant cost/limitation if asked. For a diagram, identify network boundaries and trace the links in order before naming the route.

Common mistakes

Calling the Web the Internet; confusing client/server roles with physical topology; saying a switch routes between IP networks; and calling fibre “wireless” because it carries light.

08A — adapted from HCI 2024 Q1. Explain how a switch and router differ in forwarding decisions. Identify which is needed to connect a classroom LAN to a separate library IP network.

08B — original. Two neighbouring buildings need a high-capacity link in an electrically noisy environment. Recommend a medium with two relevant reasons. Separately, justify client–server for confidential employee files and give one limitation.

Hints

Link each reason to the stated environment. “Better” or “faster” without a comparison mechanism is weak.

Revision checklist

• 08.1 Explain LAN, WAN, internetwork, Internet and intranet and distinguish their scopes.
• 08.2 Describe network benefits and costs in a stated organisational scenario.
• 08.3 Identify sender, receiver, message, medium and protocol.
• 08.4 Compare client-server with peer-to-peer architecture and justify a choice.
• 08.5 Explain roles of NIC, hub/repeater, switch, router and other devices taught in Network1.
• 08.6 Distinguish frame forwarding by MAC address from routing by IP address.
• 08.7 Compare transmission media and simplex, half-duplex and full-duplex modes where taught.
• 08.8 Explain why communication protocols and layered designs are needed.
• 08.9 Read a network diagram and describe a message’s route between hosts.

Visual revision mindmap

Open this mindmap and its text version · All 21 mindmaps

Your mindmap framework

Centre: Network foundations, hardware and architectures. Build the six branches below. For each subbranch, add a short definition, a labelled sample and one exam trap from memory; then check the chapter.

flowchart LR
    C["08 • Revision map"]
    C --> B0["Network purpose and scope"]
    C --> B1["Communication ingredients"]
    C --> B2["Hardware decisions"]
    C --> B3["Logical architecture"]
    C --> B4["Links and topology"]
    C --> B5["Visual checks and mistakes"]

• Network purpose and scope

  • Share data, services and devices.
  • Benefits: access, communication, central administration.
  • Costs: equipment, management, outages and exposure.
  • LAN, WAN, internetwork, Internet and intranet.

• Communication ingredients

  • Sender, receiver, message.
  • Transmission medium.
  • Protocol: agreed format and exchange rules.
  • Simplex, half-duplex and full-duplex.

• Hardware decisions

  • NIC: network interface.
  • Hub/repeater: repeat or regenerate signals.
  • Switch: LAN frame forwarding by destination MAC.
  • Router: next hop between IP networks; access point bridges wireless clients.

• Logical architecture

  • Client requests; server provides.
  • Central permissions and backup.
  • Peer can request and provide resources.
  • Compare cost, administration and service availability.

• Links and topology

  • Copper: cost, distance and interference.
  • Fibre: capacity, distance and electromagnetic interference.
  • Wireless: mobility, range and shared medium.
  • Star, mesh, bus, ring; identify actual failure consequences.

• Visual checks and mistakes

  • Draw classroom LAN → router → separate network.
  • Label hardware role rather than box marketing name.
  • Recommend using requirement → feature → consequence.
  • Avoid: Internet = Web; peer-to-peer = physical mesh; switch = router.

Close the notes and test the map: explain one branch aloud, sketch its sample, then answer a linked practice question. Mark any missing link to revisit.

Source trail

9569 §§4.1.1,4.1.3,4.1.5; school Network1 and Network2.

HCI 2022 Q4(a); 2024 Q1(d); 2025 Q2(a–b).

Source guide records provenance and original-paper locations.