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Communication

Communication

Networks: LAN and WAN

Networks including the internet AS Level 12 min read

On this page
  1. What you need to be able to do
  2. Why connect computers?
  3. LAN and WAN
  4. Mark-scheme focus
  5. Worked examples
  6. Summary
  7. Can I do this?
  8. Quiz

What you need to be able to do

Syllabus 2.1 Networks including the internet
  • 2.1Explain the purpose and benefits of connecting computers in a network.
  • 2.1Describe the characteristics of a LAN and a WAN, and the differences between them.
  • 2.1Decide whether a given network is a LAN or a WAN and justify it.

This is the first page of the chapter. Next: Client-server and peer-to-peer.

Why connect computers?

A network is two or more computers (and other devices) connected so they can exchange data. Each benefit below is a reason to connect the computers to each other; the network need not be connected to the internet at all.

BenefitExample in an office or school
Share files / data and communicate (messages, email)everyone works on the same up-to-date customer database
Share hardwareone printer or scanner used by 30 computers
Share software (licences installed once on a server)one site licence for a program, installed centrally
Central management: backups, security, software updates, user accountsthe technician backs up every user's work from one place each night
Users can log in from any computer and reach their own filesa student uses any machine in any lab

Drawbacks to know: the cost of hardware (switches, cabling, server) and of a skilled technician; if the server or a central device fails, many users are affected; viruses and hackers can spread through the network, so security must be managed.

LAN and WAN

A LAN (local area network) connects devices over a small geographical area (one building or site), using infrastructure (cables, switches) that is privately owned / dedicated by the organisation.
A WAN (wide area network) connects devices or LANs over a large geographical area (cities, countries), using external / public infrastructure (leased lines, the telephone network, satellites) owned by other companies: non-dedicated hardware.
LAN (Lahore office)Routerleased line / internetRouterLAN (Karachi office)
A WAN is often several LANs joined through routers and other companies' lines. The internet is the largest WAN.
LANWAN
Areasmall: a room, building or sitelarge: between cities or countries
Who owns the linksthe organisation (private / dedicated)external companies (telecoms providers): public / leased / non-dedicated
Connectionsusually physical (cables) or Wi-Fi in the buildingoften virtual: data shares other people's lines
Data transfer ratehigherlower
Securityeasier to secure (protection is easier to implement)harder: data passes through infrastructure you don't control
Mediacopper / fibre cable, Wi-Fifibre, telephone lines, microwave, satellite, cell network
“A LAN covers a local area and a WAN covers a wide area” just expands the acronyms and was not credited (June 2023). Say small / large geographical area, and add a second, different point: ownership of the infrastructure, or the transfer rate.
“A LAN is faster” is too vague. The credited version: “the rate of transfer of data in a LAN is greater than in a WAN”.

1 One school building

A school connects 200 computers in one building. LAN or WAN? Justify.

Askedtype + 2 reasonsKnowone building; school's own cablesRoutearea + ownership

  1. LAN
  2. It covers a small geographical area (one building)
  3. The school owns the cabling and switches: it does not lease external infrastructure

2 Branches in three cities

A bank links its offices in three cities. LAN or WAN?

Askedtype + reasonsKnowcities apart; leased linesRoutearea + ownership

  1. WAN
  2. It covers a large geographical area
  3. It must use external infrastructure (lines owned by telecoms companies)

3 A home network

A family's laptops, phones and printer share one Wi-Fi router. LAN or WAN?

AskedtypeKnowone houseRoutearea

  1. LAN: a small area, privately owned router

It is still a LAN even though the router also connects to the internet: the internet is a separate WAN it reaches.

Mark-scheme focus

Benefits of a LAN, then characteristics of a LAN (4 marks)

9618/12/M/J/23 Q1Paper 1 · Theory fundamentalsParts (a) and (b)4 marksFull size
A company has a LAN. (a) Give two benefits of connecting computers to a LAN. [2] (b) Give two characteristics of a LAN. [2]
Credited
  • (a) Allows the sharing of files / data // allows communication between the devices B1; allows the sharing of resources, e.g. hardware / software // central management (backup, security) B1
  • (b) Covers a small geographical area B1; the infrastructure is privately owned // not controlled by external organisations B1
Not credited
  • (a) “a LAN gives each computer access to the internet” (no internet in the question)
  • (a) answers comparing a LAN with a WAN
  • (b) “a LAN covers a local area” (repeats the acronym)
Why

Benefits = why connect the computers; characteristics = what a LAN is. The June 2023 report saw the two confused.

From: 9618/12/M/J/23 Q1(a), (b)

Two differences between a WAN and a LAN (2 marks)

9618/13/M/J/23 Q2Paper 1 · Theory fundamentalsPart (a)2 marksFull size
A university has two sites, all computers connected as a WAN. (a) Identify two differences between a WAN and a LAN. [2]
Credited
  • WAN covers a large geographical area and LAN covers a small geographical area B1
  • LAN connections are usually physical, WAN connections often virtual // LAN has a higher data transfer rate than a WAN // LAN ownership is private; WAN can be private or public // LAN usually more secure B1
Not credited
  • “LAN is local, WAN is wide”
  • “LAN is faster than a WAN” (say data transfer rate)
  • One-sided statements (each difference must compare both)

From: 9618/13/M/J/23 Q2(a)

  • LAN / WAN in most networks questions: characteristics, differences or justify a choice (2-3 marks).
  • Best second points: ownership of the infrastructure (private vs external / leased) and data transfer rate.

Worked examples

Example 1 · LAN or WAN? Justify (Paper 1, 3 marks) ★ Easy
9618/11/O/N/21 Q8Paper 1 · Theory fundamentalsPart (a)3 marksFull size
A school is setting up a network within one of its buildings. (a) State whether the network will be a LAN or a WAN. Justify your choice. [3]
1 Read it with me what is actually happening?

One building, set up by the school itself. One mark for the choice, two for two different reasons.

  • within one of its buildingssmall area
  • justifytwo separate reasons
2 What is it asking for? the target, part by part
  • (a)LAN + 2 reasons3
3 What do we know? everything the question gives us
  • one building
  • school sets it up
4 Plan the route work backwards from what we want
FindKey ideaAlready have itWork out firstTrap
  • ChoiceLAN
    • Reason 1small geographical area
    • Reason 2no external infrastructure
Which reason did most candidates miss?

The second one: the report said most only gave the area.

5 Now solve it have a go on paper first, then open the worked solution
  1. LAN B1
  2. It covers a small geographical area (one building) B1
  3. It does not lease external infrastructure / transmission media // it doesn't use the internet to transmit within the building B1
6 Check it does the answer make sense?

Two different reasons: size AND ownership ✓.

Example 2 · Two ways a WAN differs from a LAN (Paper 1, 2 marks) ★ Easy
9618/12/M/J/25 Q6Paper 1 · Theory fundamentalsPart (a)2 marksFull size
A company has multiple sites in different cities; drivers connect to the company's WAN using smartphones. (a) State two ways that a WAN is different to a LAN. [2]
1 Read it with me what is actually happening?

Each “way” must compare both networks on one feature.

  • different tosay what the WAN does AND what the LAN does
2 What is it asking for? the target, part by part
  • (a)two differences2
3 What do we know? everything the question gives us
    4 Plan the route work backwards from what we want
    FindKey ideaAlready have itWork out firstTrap
    • Differences
      • Arealarge vs small
      • Hardwarenon-dedicated vs dedicated
      • Mediaexternal vs company-owned
    5 Now solve it have a go on paper first, then open the worked solution
    1. In a WAN devices connect over a larger geographical area, in a LAN over a smaller area B1
    2. A WAN may use non-dedicated hardware / external, not company-owned transmission media; the LAN's are usually dedicated / company-owned B1
    6 Check it does the answer make sense?

    Each line names both networks ✓.

    Example 3 · Characteristics of a WAN (Paper 1, 2 marks) ★ Easy
    9618/13/O/N/24 Q9Paper 1 · Theory fundamentalsPart (a)2 marksFull size
    A computer is connected to a LAN that connects to a WAN. (a) Describe the characteristics of a WAN. [2]
    1 Read it with me what is actually happening?

    Two features of a WAN on its own (no comparison needed this time).

    • characteristicswhat a WAN is like
    2 What is it asking for? the target, part by part
    • (a)two characteristics2
    3 What do we know? everything the question gives us
      4 Plan the route work backwards from what we want
      FindKey ideaAlready have itWork out firstTrap
      • WAN
        • Arealarge
        • Infrastructureexternal / public
        • Hardwarenon-dedicated
      5 Now solve it have a go on paper first, then open the worked solution
      1. A WAN covers a large geographical area B1
      2. External / public infrastructure is used // non-dedicated hardware B1
      6 Check it does the answer make sense?

      Neither point repeats the words “wide area” ✓.

      Summary

      • Networks let computers share data, hardware and software, and be managed centrally.
      • LAN: small area, privately owned / dedicated infrastructure, higher transfer rate.
      • WAN: large area, external / public / leased infrastructure, non-dedicated hardware, lower transfer rate. The internet is a WAN.
      If you see…do this
      “benefits of a LAN”sharing data / hardware / software, central management - not internet access
      “characteristics of a LAN / WAN”area + ownership of infrastructure (+ transfer rate)
      “LAN or WAN? justify”choice + two different reasons

      Can I do this?

      Anything unticked: revise that section first. All ticked: take the quiz.

      Quiz

      The multiple-choice and guided questions need JavaScript. The concept checks and exam practice below work without it.

      Concept checks

      Answer each one in your head first, then open it.

      1Is the internet a LAN or a WAN?Show answer

      A WAN - the largest one: a network of networks spread across the world on infrastructure owned by many companies.

      2Why is data usually slower across a WAN?Show answer

      It travels further, through many routers and shared lines owned by others, often with less bandwidth per user.

      3Can a LAN use Wi-Fi?Show answer

      Yes: wired or wireless, it is still a LAN if it covers a small area on the organisation's own equipment.

      Exam-style practice

      New questions, not used above. Do them on paper, then mark your work against the official mark scheme.

      Q1Past-paper style4 marks

      A college has three buildings on one campus. Each building has its own network, and the three networks are joined by cables the college owns.

      1. (a)
        State whether the whole campus network is a LAN or a WAN. Justify your choice.
        [3]
      2. (b)
        Give one benefit to the college of connecting its computers in a network.
        [1]
      Show the mark scheme
      PartAnswer / workingMarksGuidance
      (a)LANB1
      Covers a small geographical area (one campus)B1
      The college owns the infrastructure / cabling; no external (leased) lines are usedB1
      (b)e.g. share files / data; share hardware such as printers; share software; central management of backups / securityB1
      Total: 4 marks
      Q2Past-paper style2 marks

      A supermarket chain connects the tills in all its stores across the country to a head office.

      Describe two characteristics of the network used.

      1. [2]
      Show the mark scheme
      PartAnswer / workingMarksGuidance
      It is a WAN covering a large geographical areaB1
      It uses external / public / leased infrastructure // non-dedicated hardware // lower data transfer rate than a LANB1
      Total: 2 marks

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