A-Level Computer Science / Unit 2: Networks, Connectivity and the Internet

2.1.5 LAN Hardware and Device Roles

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2.1.5 LAN Hardware and Device Roles

A local area network works because several pieces of hardware cooperate. Some components attach an end device to the network, some forward traffic, some provide shared services, and others extend or divide the network.

This section focuses on switches, servers, Network Interface Cards (NICs), Wireless Network Interface Cards (WNICs), Wireless Access Points (WAPs), cables, bridges and repeaters.

By the end of this section, you should be able to:

  • state the purpose of each required LAN hardware component;
  • distinguish a NIC from a WNIC and a WAP;
  • explain how a switch forwards frames within a LAN;
  • describe how a server provides shared network services;
  • compare a bridge with a repeater;
  • trace data through a simple wired or wireless LAN.

Organise LAN hardware by its job

Learning the devices as an unrelated list makes them easy to confuse. A more useful approach is to group them by the job they perform.

Job in the LAN Hardware Main purpose
Connect an end device NIC, WNIC and cable Provide the physical and data-link connection used by the device.
Forward local traffic Switch Send frames towards the correct port inside the LAN.
Provide shared resources Server Offer services such as files, authentication, applications or printing.
Join wireless devices to the LAN Wireless Access Point Exchange radio signals with wireless clients and bridge them into the wired LAN.
Join or divide LAN sections Bridge Connect segments and filter traffic according to device addresses.
Extend a signal path Repeater Regenerate a weakened signal so that it can continue travelling.

Exam tip

Define hardware through its function. “A switch is in the centre” is a location; “a switch learns addresses and forwards frames to the appropriate port” explains what it does.

NICs, WNICs and cables

Network Interface Card (NIC)

A Network Interface Card allows an end device to communicate on a network. It may be a separate expansion card or built into the device's motherboard.

NIC: the network interface that enables a device to send and receive data through a wired network connection.

A NIC has a hardware address, commonly called a MAC address. Switches use source addresses they observe to learn which devices are reachable through particular ports.

Wireless Network Interface Card (WNIC)

A WNIC performs the network-interface role using radio communication rather than a direct data cable. Laptops, tablets and phones often contain a built-in WNIC.

WNIC: a wireless network interface that enables an end device to communicate with a wireless access point.

Cables

In a wired LAN, cables carry signals between devices and connecting hardware. Copper twisted-pair cable is common between end devices and switches. Fibre-optic cable may be used where higher capacity, longer distance or immunity to electrical interference is required.

Connection Likely hardware path
Desktop to switch Desktop NIC → copper Ethernet cable → switch port
Switch to server Switch port → copper or fibre link → server NIC
Laptop to LAN Laptop WNIC → radio link → WAP → cable → switch
Two LAN sections Switch or bridge → copper/fibre link → switch or bridge

Common mistake

A NIC is not merely the socket on the outside of a computer. The socket is part of the connection; the NIC is the interface hardware that sends, receives and processes network frames.

Switches

A switch connects multiple devices within a LAN. It receives an Ethernet frame on one port, examines its destination MAC address and decides where to forward it.

Switch: a multi-port LAN device that learns which MAC addresses are reachable through its ports and forwards frames towards the intended destination.

How a switch learns

  1. A frame arrives on a switch port.
  2. The switch reads the source MAC address.
  3. It records that the source is reachable through the incoming port.
  4. It checks the destination MAC address.
  5. If the destination is known, it forwards the frame through the relevant port.
  6. If the destination is unknown, it sends the frame through other appropriate ports so it can reach the destination.

Why switches are useful

  • Different pairs of devices can communicate without every frame being sent to every port.
  • Traffic is separated into individual switch links.
  • Devices can be added when spare ports and capacity are available.
  • One damaged end-device cable normally affects only that device.

Common mistake

A switch does not choose routes between different IP networks. That is the role of a router. A switch primarily forwards frames within a LAN.

Servers

A server is a computer or system configured to provide services to clients. The word describes its role, not one fixed shape of hardware.

Server: a system that responds to requests and provides a network service to client devices or applications.
Server role Service provided Example request
File server Stores and manages shared files A teacher opens a departmental document.
Authentication server Checks usernames, passwords and access rights A student signs in to the school network.
Print server Receives and manages print jobs Several computers submit work to one printer queue.
Application or database server Runs shared software or stores structured data A receptionist searches a booking system.

Server hardware considerations

  • Servers may need greater processing, memory and storage capacity than ordinary clients.
  • They are often designed for continuous operation and may use redundant components.
  • A server still needs one or more NICs to communicate with the LAN.

Exam tip

Name the service and the benefit. For example, “a file server stores shared documents, allowing authorised users to access the same managed files”.

Wireless Access Points

A Wireless Access Point creates a wireless connection point for devices fitted with WNICs. It exchanges data by radio with wireless clients and normally connects by cable to the wired LAN.

Wireless Access Point (WAP): a device that connects wireless clients to a LAN and transfers data between the wireless and wired parts of the network.

What a WAP does

  • Provides access to a wireless network.
  • Receives radio transmissions from WNIC-equipped devices.
  • Passes traffic between wireless clients and the wired LAN.
  • Applies wireless security settings such as authentication and encryption.
  • Provides coverage over a limited area; larger sites may need several WAPs.

WAP versus WNIC

Hardware Where it is used Role
WAP Installed as network infrastructure Connects many wireless clients to the LAN.
WNIC Installed in an end device Allows that individual device to communicate wirelessly.

Common mistake

A WAP and a WNIC are not alternatives. They work together: the WNIC is in the client, while the WAP provides the wireless connection into the LAN.

Bridges and repeaters

Repeater

A repeater works with the signal itself. It receives a weakened or distorted signal, regenerates it and sends a fresh version onwards. It does not examine destination addresses.

Repeater: a device that regenerates a signal so that it can travel further.

Bridge

A bridge connects LAN segments and makes forwarding decisions using MAC addresses. It learns which devices are located on each side and can stop unnecessary frames from crossing.

Bridge: a device that joins LAN segments and filters frames according to MAC addresses.
Comparison Repeater Bridge
Main problem solved Signal weakening over distance Connecting and separating traffic between LAN segments
Uses device addresses? No Yes, MAC addresses
Traffic handling Regenerates the incoming signal Filters or forwards according to the destination
Relationship to a switch Different function A modern switch performs a similar bridging function across many ports

Common mistake

A bridge does not strengthen a weak signal, and a repeater does not learn addresses. They solve different problems.

Follow a request through a mixed LAN

A student uses a wireless laptop to request a document from a file server:

  1. The laptop's WNIC sends the frame by radio.
  2. The WAP receives it and passes it into the wired LAN.
  3. A cable carries the frame from the WAP to the switch.
  4. The switch examines the destination MAC address and forwards the frame towards the server.
  5. The server's NIC receives the frame.
  6. The file server processes the request and sends a response.

Exam tip

Trace hardware in order: WNIC transmits → WAP connects wireless to wired → switch forwards → server responds.

Interactive: LAN Hardware Explorer

Use the existing explorer to compare hardware in a bus, star and wireless LAN. The bus mode provides useful historical context for repeaters; star and wireless modes show hardware more typical of current LANs.

Bus LAN

End-system Cable / link LAN hardware Signal path

Practice

Explain the device

  1. Explain the role of a NIC in a wired LAN.
  2. Explain the difference between a WNIC and a WAP.
  3. Describe how a switch decides where to forward a frame.
  4. Explain why a server requires a NIC even though it provides services.
  5. Explain why a repeater does not reduce unnecessary traffic between LAN segments.
  6. Explain how a bridge can reduce traffic crossing between two LAN segments.

Select the hardware

  1. A new desktop must be connected by cable to a switch.
  2. A tablet must join the school LAN without a cable.
  3. A long signal path is unreliable because the signal is weak.
  4. Two LAN segments must be joined while unnecessary traffic is filtered.
  5. Thirty computers need central file storage and managed access.
  6. A wireless classroom must connect to the existing wired LAN.

For each situation, name the relevant hardware and explain its function.

Review

Hardware Main function Do not confuse it with...
NIC Connects a device to a wired LAN and handles frames The external socket alone
WNIC Connects an end device wirelessly A WAP
WAP Connects wireless clients to the LAN A wireless interface inside one client
Switch Forwards LAN frames according to MAC addresses A router between IP networks
Server Provides a service to clients A switch that only forwards traffic
Bridge Joins LAN segments and filters frames A repeater
Repeater Regenerates a weakened signal A bridge that examines addresses
Cable Carries signals between wired devices The interface hardware at either end

Quick self-check

  1. Can I state the role of every hardware item named in the syllabus?
  2. Can I distinguish forwarding, filtering, signal regeneration and service provision?
  3. Can I trace a frame from a wireless client to a server?
  4. Can I explain why a switch is not a router?