Pack — 2 Communication (AS Level)

Pack — 2 Communication

Question-and-answer mirror of Jigsaw. Every concept in Jigsaw appears here as a !question with a collapsible !success answer.

How marks are set

• 9618 | — the highest mark tariff that concept has ever carried in a 9618 paper. Answer points = that tariff + 2 spare, newest mark scheme first, older ones filling the gaps.
• 9608 | — same rule, using 9608 tariffs. In the 9618 syllabus, untested in the current series.
• Inferred | — not tested in either series. Tariff estimated from how 9618 marks comparable questions.
• SME | — from the Save My Exams notes. Tariff estimated the same way. Weigh against the mark schemes.

Answers are written as mark-scheme bullet points, not prose. One bullet = one mark, unless the bullet begins … (an expansion of the point above it).

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2.1.1 Purpose and benefits of networking devices

Question

Give two benefits of connecting computers to a LAN.

Answer — 4 points for 2 marks

• Allows the sharing of files / data // allows communication between the devices
• Allows the sharing of resources, e.g. hardware / software (applications)
• Allows central management // by example, backup, security, etc.
• Allows access to reliable central data, e.g. from a file server

Latest: 9618_s23_qp_12_sc_1.a

Question

Give two drawbacks to a company of networking its standalone computers.

Answer — 4 points for 2 marks

• Expensive to set up, because cabling and servers must be bought
• If the server fails, the whole network is affected // single point of failure
• Malware or hacking can spread to every machine on the network
• Large networks are difficult to manage and need a skilled administrator

Tariff set to 2 by symmetry with the benefits question above.

Question

A small business has six standalone computers. Explain why the business should connect them as a network.

Answer — 5 points for 3 marks

• Files and data can be shared directly between employees …
• … rather than being transferred by removable media
• Hardware such as a printer can be shared, reducing cost
• Data can be backed up centrally, so it is not lost if one machine fails
• A network manager can control access rights and internet usage

Tariff set to 3 to match 9618_w21_qp_11_sc_8.a, the nearest “justify” question.

Question

State what is meant by a network and give its purpose.

Answer — 4 points for 2 marks

• Two or more interconnected devices (computers, printers, servers)
• The purpose is to share resources
• … and to exchange data
• … and to allow communication and collaboration between users

Tariff set to 2: 9618 marks “state what is meant by” at 1–2.

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2.1.2 Characteristics of a LAN and a WAN

Question

Describe the characteristics of a LAN (local area network).

Answer — 4 points for 2 marks

• Covers a small geographical area
• Normally privately owned // dedicated infrastructure // not controlled by external organisations
• Can use wired or wireless communication
• Has a high data transfer rate

Latest: 9618_w25_qp_12_sc_5.a

Question

Describe the characteristics of a WAN (wide area network).

Answer — 4 points for 2 marks

• Covers a large geographical area
• External / public infrastructure is used
• Non-dedicated hardware
• Connections are often virtual rather than physical

Latest: 9618_w24_qp_13_sc_9.a

Question

State two ways in which a WAN is different from a LAN.

Answer — 4 points for 2 marks

• A WAN covers a large geographical area; a LAN covers a small geographical area
• A WAN may use non-dedicated hardware; the hardware in a LAN is usually dedicated
• A WAN uses external / not company-owned transmission media; a LAN’s transmission media is usually company owned
• A LAN has a high data transfer rate; a WAN has a lower data transfer rate

Latest: 9618_s25_qp_12_sc_6.a. 9618_s23_qp_13_sc_2.a adds: the ownership of a LAN is private, a WAN can be private or public; a LAN is usually more secure because protection is easier to implement.

Question

A school is setting up a network within one of its buildings. State whether this will be a LAN or a WAN and justify your choice.

Answer — 5 points for 3 marks

• LAN
• Small geographical area
• No leasing of external infrastructure / transmission media // does not use the internet to transmit within the building
• The hardware is owned by the school
• The connections between devices are physical

Latest: 9618_w21_qp_11_sc_8.a

Question

State what is meant by a WLAN and give one benefit of a WLAN over a wired LAN.

Answer — 4 points for 2 marks

• A LAN in which devices connect wirelessly instead of by cable
• Wireless Access Points (WAPs) are added so devices can connect using Wi-Fi
• Benefit: users can connect anywhere within range of a WAP without extra cabling
• Benefit: extra devices or extra coverage can be added by adding more WAPs

Tariff set to 2: the syllabus notes name WiFi, and 9618 marks “state + one benefit” at 2.

Question

Describe two advantages and two disadvantages of a WLAN.

Answer — 6 points for 4 marks

• Advantage: users can connect anywhere in range of a WAP without additional hardware or wiring
• Advantage: usable indoors and out, so highly flexible
• Advantage: more WAPs can be added easily to extend coverage or user numbers
• Disadvantage: limited coverage, further affected by walls and other structures
• Disadvantage: bandwidth suffers in high-traffic areas
• Disadvantage: vulnerable to interception, because signals travel through the air

Tariff set to 4 to match 9618_s21_qp_11_sc_4.b (two drawbacks, 2 marks each).

Question

Describe how a WAN is made up.

Answer — 4 points for 2 marks

• A WAN is a collection of LANs joined together
• The LANs are connected via routers
• The connecting hardware is not owned by the organisation, e.g. telephone lines owned by a telecoms company
• WANs use fibre-optic cable, telephone lines and satellite to connect the LANs

Tariff set to 2 to match the “characteristics of a WAN” question.

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2.1.3 Client-server and peer-to-peer models

Question

A bank allows customers to access their accounts using an application on a smartphone. This is a client-server model. Describe the roles of the different devices in this model.

Answer — 6 points for 4 marks

• Identification of the server in the scenario (the bank’s server)
• The server receives the requests and processes them
• Identification of the client in the scenario (the customer’s smartphone / the app)
• The client sends the request to the server, waits, and outputs the response
• The server stores all the data
• The server returns the results to the client

Latest: 9618_s24_qp_11_sc_5.a

Question

Users play a game in a virtual world from any computer with internet access using a web browser. Explain the reasons why the statement “this computer game uses a client-server model” is correct.

Answer — 6 points for 4 marks

• A web server stores all the data for each player
• Each player is on a client computer // the player’s web browser is the client
• … that sends requests over the internet to the web server
• The server performs the required action in the game
• The server updates the data in the game
• The server sends the results to the player

Latest: 9618_s25_qp_13_sc_3.c

Question

Describe the key features of a peer-to-peer network.

Answer — 4 points for 2 marks

• All computers are of equal status
• Each computer provides access to resources and data // data is distributed
• Computers can communicate and share resources directly
• Each computer is responsible for its own security

Latest: 9618_s21_qp_11_sc_4.a

Question

Describe two drawbacks of using a peer-to-peer network. (2 marks per drawback — each needs an expansion.)

Answer — 6 points for 4 marks

• Reduced security // no central management of security …
• … only as secure as the weakest computer on the network // each computer is at risk from viruses on the others
• No central management of backup …
• … if the data on one computer is not backed up it is lost to all of them
• No central management of files / software, so consistency is difficult to maintain
• All computers must be switched on to share files, so files may not always be available

Latest: 9618_s21_qp_11_sc_4.b. Also creditable: individual computers respond more slowly because they are being accessed by others.

Question

Give two benefits of using the client-server model.

Answer — 4 points for 2 marks

• Files and resources are centralised
• Security can be created and managed centrally // a username and password is needed to access the network
• Centralised backup
• Clients can be less powerful machines, therefore less expensive to buy

Latest: 9608_w15_qp_13_sc_7.a.ii. Also creditable: intranet capability; internet monitoring.

Question

Describe what is meant by a client-server model of networked computers.

Answer — 4 points for 2 marks

• At least one computer is used to “serve”
• … other computers are referred to as “clients”
• The server provides services / applications
• … which may be requested by the clients

Latest: 9608_w15_qp_13_sc_7.a.i

Question

A company has an email server. Identify three other types of server.

Answer — 5 points for 3 marks

• File server
• Print server
• Proxy server
• Web server
• Application server

Latest: 9608_s19_qp_12_sc_1.d

Question

Explain how a client-server model is used when a customer logs in to a bank’s system.

Answer — 5 points for 3 marks

• All data is held on the server // all processing is performed on the server
• The server only sends the results of the query to the client
• The client does not have access to all the data
• … which keeps the data more secure / consistent
• Customers can be identified when they log in, from a database of usernames and passwords

Latest: 9608_w19_qp_11_sc_4.b

Question

Give two benefits of using a peer-to-peer network instead of a client-server network.

Answer — 4 points for 2 marks

• Cheaper to set up, because no dedicated server is needed
• Easy to set up, because no administrative staff are needed
• No dependency on a central server // no single point of failure
• Data can be shared directly between machines without going through a server

Tariff set to 2 to match the P2P features question; 9618 has never asked this half.

Question

A large company needs a network for 200 employees, with centrally managed security. Identify the most appropriate network model and justify your choice.

Answer — 6 points for 4 marks

• Client-server
• Files and resources are centralised, so all employees access the same up-to-date data
• Security is managed centrally, so access rights can be set for each user
• Backup is centralised, so data is not lost if one machine fails
• Peer-to-peer is not suitable, because it has no central control of security
• … and it performs poorly on a network of this size

Tariff set to 4: the syllabus notes require justification, and 9618_s23_qp_13_sc_5.b marks “identify + justify” at 4.

Question

State the type of situation in which each network model is normally used.

Answer — 4 points for 2 marks

• Client-server: larger organisations where centralised control is needed
• … and where reliability and security are paramount
• Peer-to-peer: home networks, small businesses, or file sharing
• The choice depends on security, cost, ease of setup and maintenance requirements

Tariff set to 2.

Question

Give two drawbacks of using a client-server network.

Answer — 4 points for 2 marks

• Single point of failure — if the server goes down, services are unavailable
• Expensive to set up
• … and expensive to maintain, often needing a dedicated team of staff
• The server must be powerful enough to handle all requests, adding cost

Tariff set to 2. Not in any 9618 mark scheme.

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2.1.4 Thin-client and thick-client

Question

Identify two characteristics of a thin-client and describe how each is used in a given software system. (1 mark characteristic + 1 mark application, ×2.)

Answer — 6 points for 4 marks

• Data is not stored on the client computer … the data is stored on the server instead
• The client computer is reliant on access to the server … the user cannot work if the server goes down
• The client is heavily reliant on the network / internet connection … the software will not operate without network access
• The client requires few local resources / little memory … low-specification devices can still run the software
• The client performs minimal functions / processes … it transmits requests and the server sends back the response
• The client only displays the results returned by the server

Latest: 9618_s24_qp_12_sc_3.b

Question

Describe what is meant by a thick-client model.

Answer — 4 points for 2 marks

• The server performs minimal / some processing for the client
• The clients do most of their own processing // work independently
• Most of the resources are installed locally on the client
• The client can function without a constant connection to the server

Latest: 9618_s23_qp_12_sc_1.e

Question

The computers in one room are set up as thin-clients in a client-server model. Describe the role of the different computers in this model.

Answer — 4 points for 2 marks

• The server performs all processes required by the task and/or data storage
• The clients only send requests to the server
• … and display the returned results
• The clients perform no processing of their own

Latest: 9618_s23_qp_13_sc_2.c

Question

Give two differences between a thin-client and a thick-client model. (2 marks per difference.)

Answer — 6 points for 4 marks

• A thin-client needs a permanent connection to the server …
• … whereas a thick-client can work independently of a server
• A thin-client uses the server’s processing power …
• … whereas a thick-client uses its own local processing power
• A thin-client does not function offline, whereas a thick-client can function offline
• A thin-client needs few local resources, whereas a thick-client has resources installed locally

Tariff set to 4: the bullet ends “and the differences between them”, and 9618 marks paired-expansion questions at 4.

Question

Describe one benefit and one drawback to an organisation of using thin-clients. (2 marks each.)

Answer — 6 points for 4 marks

• Benefit: cheaper client devices can be used … because the processing is done by the server
• Benefit: software updates and security are managed centrally … so only the server needs updating
• Benefit: new clients are easy to add
• Drawback: the server is a single point of failure … if it goes down no client can work
• Drawback: heavy dependence on the network … performance drops if the connection is slow
• Drawback: the server must be powerful, because it performs all processing

Tariff set to 4 by the pattern of 9618_s21_qp_11_sc_4.b.

Question

Give one example of a thin-client and one example of a thick-client, with a reason for each.

Answer — 4 points for 2 marks

• Thin-client: a cloud application such as Google Docs, because processing and storage happen on the remote server
• Thin-client: a supermarket POS terminal, because prices and stock are fetched from a central server
• Thick-client: installed software such as a photo editor, because it runs using the device’s own processor
• Thick-client: a standalone game installed on a PC, because it works without a network connection

Tariff set to 2. Note both can be hardware or software.

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2.1.5 Bus, star, mesh and hybrid topologies

Question

Complete a diagram to show how five computers, a server and a switch are connected in a star topology.

Answer — 3 points for 2 marks

• All computers directly connected to the switch and no other connections
• Switch connected directly to the server
• All components correctly labelled

Latest: 9618_w25_qp_12_sc_5.b

Question

An office has four wired computers, one server, two printers, one central switch and a device providing a single point of internet access, set up as a star topology. Draw and label the topology.

Answer — 6 points for 4 marks

• Server directly connected to the switch
• Four labelled computers all connected directly to the switch
• Two printers each directly connected to the switch / server / a computer
• Router or modem directly connected to the switch / server for internet access
• No other connections between devices
• All devices labelled

Latest: 9618_s25_qp_12_sc_6.d

Question

Describe how packets are transmitted between two hosts using a star topology.

Answer — 5 points for 3 marks

• The sending device sends the packets to the switch
• The switch checks the destination address on each packet
• … and sends them only to the intended receiver
• The switch uses the stored MAC addresses of the connected devices to do this
• Other devices on the network do not receive the packets

Latest: 9618_w25_qp_12_sc_5.c. 9618_s24_qp_13_sc_5.b accepts “switch/router/central device”.

Question

Describe what is meant by a mesh topology.

Answer — 4 points for 2 marks

• All computers are connected to at least one other device
• There are multiple routes between devices
• The computers can act as relays, passing packets on towards the final destination
• In a full mesh every computer is connected to every other computer

Latest: 9618_s23_qp_13_sc_2.b.i

Question

Give two advantages of using a mesh topology instead of a bus topology.

Answer — 4 points for 2 marks

• If one line goes down there are more routes available
• Improved security, as data is not sent along one main line // data is sent over a dedicated connection
• No / fewer collisions
• New nodes can be added without interruption or interfering with other nodes

Latest: 9618_s23_qp_13_sc_2.b.ii

Question

Explain one advantage of implementing a star topology instead of a bus topology in a classroom. (1 mark advantage + 1 mark expansion.)

Answer — 4 points for 2 marks

• Star is more resilient to faults … because there is no single cable, so there is less disruption
• Higher performance as there are fewer collisions … because each device connects only to the switch
• Easier to add new nodes … because each device connects directly to the switch
• Easier to fault-find compared to a bus topology

Latest: 9618_w23_qp_11_sc_2.d

Question

Tick one or more boxes in each row to identify the topology or topologies each statement describes.

Answer — 5 rows for 5 marks

• All devices connect to one central device → Star
• All devices connect to a central cable → Bus
• Multiple paths for the packets to travel → Mesh
• Robust against damage: if any line fails the rest retains full functionality → Star and Mesh
• Most likely to lose data through collisions → Bus

Latest: 9618_s24_qp_11_sc_8.a

Question

Andy’s devices all connect wirelessly to the router in his house. Identify the topology of the network and justify your choice.

Answer — 3 points for 2 marks

• Star topology
• Devices are connected directly to the router independently
• // All devices are only connected to the router

Latest: 9618_w21_qp_12_sc_3.b.i

Question

Describe what is meant by a hybrid topology and give one situation in which it would be used.

Answer — 5 points for 3 marks

• A mix of two or more different topologies, e.g. bus and star, or star and mesh
• Used when separate existing networks need to be joined together
• … for example three school sites, each with its own bus, star and mesh network, linked as one network
• Each site keeps its existing setup
• New sites can be added without redesigning the whole network

Named in the syllabus bullet and never tested in either series. Tariff set to 3 by the topology-description norm.

Question

Describe how packets are transmitted between two hosts using a bus topology.

Answer — 5 points for 3 marks

• The sending device puts the packet onto the single shared bus cable
• All devices on the cable receive / listen to the packet
• Each device checks the destination address on the packet
• Only the device whose address matches accepts it
• All other devices ignore the packet

Tariff set to 3 to match the star version, 9618_w25_qp_12_sc_5.c.

Question

Describe one drawback of a star topology and one drawback of a mesh topology. (2 marks each.)

Answer — 6 points for 4 marks

• Star: the central switch is a single point of failure …
• … if the switch fails, every device loses access to the network and its resources
• Star: expensive to install, because of the switch and the extra cabling needed
• Mesh: requires a large amount of hardware, cabling and switches …
• … so it has a high set-up cost
• Mesh: hard to scale, because adding a new device means adding many new connections

Tariff set to 4 by the pattern of paired-expansion questions.

Question

Describe how a bus topology is constructed and how devices read data from it.

Answer — 5 points for 3 marks

• All devices are connected by one single bus cable
• The cable is terminated at each end
• The terminators stop the signal bouncing back and causing errors
• Each device listens to the electrical signals on the cable
• Each device checks packets for its own address and ignores those it does not recognise

Tariff set to 3. “Terminator” appears in no mark scheme in this topic.

Question

Explain how traffic on a star topology differs when the central device is a hub rather than a switch.

Answer — 4 points for 2 marks

• A hub sends the traffic to all devices on the network
• … each device checks the address and accepts it if it matches, otherwise ignores it
• A switch sends the traffic only to the device whose address matches
• So a hub creates unnecessary traffic and is less secure

Tariff set to 2.

Question

Describe the difference between a full and a partial mesh, and describe two ways packets can travel on a mesh network.

Answer — 6 points for 4 marks

• Full mesh: every computer is connected to every other computer
• Partial mesh: only some devices are interconnected, which is cheaper and more practical
• Routing: devices are given routing logic so packets are sent by the shortest route
• … each device acts like a router
• Flooding: all packets are sent to all devices with no routing logic
• … which can cause network flooding and performance problems

Tariff set to 4. Neither “partial mesh”, “routing” nor “flooding” appears in a mark scheme here.

Question

Give two advantages and two disadvantages of a hybrid topology.

Answer — 6 points for 4 marks

• Advantage: combines the strengths of each topology, e.g. the reliability of mesh with the simplicity of bus
• Advantage: flexible — different parts of the network can be optimised for different needs
• Advantage: scalable — new segments can be added without changing the whole setup
• Advantage: a failure in one part does not necessarily affect the rest
• Disadvantage: complex to design, needing careful planning to combine different topologies
• Disadvantage: expensive, and harder to troubleshoot because different parts follow different rules

Tariff set to 4.

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2.1.6 Cloud computing

Question

Give two benefits of storing data using cloud computing.

Answer — 6 points for 2 marks

• Cloud storage can be free of charge for a limited amount
• There is no need for personal storage devices
• The data can be accessed from any computer with an internet connection
• Cloud data services usually include data backup and recovery services
• It is easier to share data / collaborate with colleagues
• Storage capacity can be quickly and easily increased if needed

Latest: 9618_w25_qp_12_sc_8.a.i

Question

Give two drawbacks of using cloud computing.

Answer — 6 points for 2 marks

• The cloud can only be accessed with an internet connection
• There may be no backups // no control over backups // reliance on a third party for backups
• Uploading / downloading data could take a long time
• Potential issues with the cloud storage company, e.g. downtime or technical problems
• Limited storage availability without paying extra, so possibly more expensive in the long term
• Possible security and compatibility issues

Latest: 9618_w25_qp_12_sc_8.a.ii

Question

Define the term private cloud.

Answer — 3 points for 1 mark

• Dedicated / bespoke services or storage on a remote server
• … available only to that company
• Not shared with other organisations

Latest: 9618_s24_qp_13_sc_5.a.i

Question

Describe the benefits to a company of using private cloud storage instead of public cloud storage.

Answer — 5 points for 3 marks

• Not reliant on a third party
• … gives greater control over security / privacy
• … gives greater control over backup
• Storage can be tailored / scaled to the company’s requirements
• … by example, e.g. the amount of storage accessible, or easier sharing of files

Latest: 9618_s24_qp_13_sc_5.a.ii

Question

Explain why a company that sells online courses stores them on a public cloud.

Answer — 4 points for 2 marks

• The courses must be available to anyone who wishes to follow them
• The courses must be available on the internet
• The company is willing to share infrastructure with other companies
• … which is more economic for the company

Latest: 9618_w23_qp_13_sc_3.a.i

Question

Describe two disadvantages of storing data on a public cloud compared with storing it on a server in a LAN. (2 marks each.)

Answer — 6 points for 4 marks

• There could be a possible loss of control, unlike with the LAN …
• … because the data is stored on a remote / someone else’s infrastructure
• … reliance on an external agency to complete tasks such as backups and security
• Requires a reliable internet connection …
• … to ensure access to the remote data, which is more likely with a LAN
• Increased recurring costs, as cloud provider charges must be paid, whereas LAN costs are paid once only

Latest: 9618_w23_qp_13_sc_3.a.ii

Question

A diagram shows a laptop, a firewall, device A, an ISP, cloud X and application B. Complete the table.

Answer — 3 rows for 3 marks

• The name of device A that allows the laptop to connect to the internet → Router
• A type of cloud, X → Public (cloud)
• An example of an application, B, that can run on the cloud → Email / graphics / word processor / spreadsheet / game / database

Latest: 9618_w22_qp_13_sc_7.a

Question

State two differences between a public cloud and a private cloud.

Answer — 4 points for 2 marks

• A public cloud is owned and managed by a third-party provider, whereas a private cloud is owned and managed by the company itself
• A public cloud is shared with other organisations, whereas a private cloud is restricted to one organisation
• A public cloud is cheaper because infrastructure is shared; a private cloud costs more because the company pays for hardware, maintenance and staff
• A public cloud gives less control over security, whereas a private cloud allows custom security policies and full oversight

Tariff set to 2: private has been defined at 1 mark, so the two-way comparison is a 2.

Question

Explain the benefits to a company of accessing its software using cloud computing.

Answer — 5 points for 3 marks

• The software can be used on any device with an internet connection
• There is no need to install the software on each machine
• Updates and patches are handled automatically by the provider
• No specialist IT staff are needed to maintain the software
• The plan can be scaled up or down as the company’s needs change

Tariff set to 3: 9618_s21_qp_12_sc_5.c mentions software but has never been examined, and 3 matches the private-cloud-benefits question.

Question

Describe the difference between cloud storage and cloud software.

Answer — 4 points for 2 marks

• Cloud storage is long-term storage of data on remote servers in data centres
• … accessed only over the internet
• Cloud software is an application hosted and managed remotely, used on demand
• … with the provider handling maintenance, upgrades and security, usually for a subscription

Tariff set to 2.

Question

Give two drawbacks of using cloud software.

Answer — 5 points for 2 marks

• It will not work properly offline
• Performance depends on the internet connection speed
• Ongoing subscription cost
• Data privacy concerns, because your data is stored on the provider’s servers
• You remain legally responsible for personal data even though it is hosted elsewhere

Tariff set to 2.

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2.1.7 Wireless and wired networks

Question

Give three advantages of a wireless network compared to a wired network.

Answer — 5 points for 3 marks

• Devices can be more mobile as no physical connection is required
• No cabling is needed so it is easier to set up
• Easier to add additional devices
• Multiple different device types can be connected
• Cheaper to set up, because less cabling and expertise is needed

Latest: 9618_w25_qp_13_sc_4.a

Question

Give one drawback of using a wireless network.

Answer — 4 points for 1 mark

• Can be less secure
• Transmission speed can be slow
• Interference is possible
• The signal degrades quickly without repeaters / boosters

Latest: 9618_w25_qp_13_sc_4.b

Question

Copper cable can be used to transmit data in a network. Identify and describe two other transmission media that can be used to transfer data in a WAN. (1 mark medium + 1 mark description, ×2.)

Answer — 6 points for 4 marks

• Fibre optic … transmits data as pulses of light
• Radio waves / microwaves … transmits electromagnetic waves on different frequencies
• Satellite … a communication device in Earth’s orbit that receives and transmits data
• Fibre optic suffers no interference and can span long distances without degradation
• Radio waves carry data wirelessly, commonly known as Wi-Fi
• Copper cable carries data as electrical signals and can consist of a twisted pair

Latest: 9618_w24_qp_13_sc_9.b

Question

Give one advantage and two disadvantages of transmitting data using satellites instead of copper cables.

Answer — 5 points for 3 marks

• Advantage: not fixed to a single location // allows access in remote / rural areas
• Disadvantage: high latency / lag / slow to connect
• Disadvantage: more expensive than wired methods, as extra equipment is needed
• Disadvantage: the signal is affected by bad weather
• Disadvantage: transmission speed is slower than fixed-line broadband // direct line of sight is needed

Latest: 9618_w22_qp_13_sc_7.b

Question

Explain the benefits to users of allowing them to use both wired and wireless connections.

Answer — 6 points for 4 marks

• Some users may only have one sort of connection available on their device
• Wired provides better performance for the device … for example enabling faster access to databases
• There will be less interference if users connect via a cable
• Users can transmit private / confidential data securely … for example their final dissertation
• Wireless means devices can be used in different rooms / sites / outside more freely // devices can be portable
• Wireless enables users to bring multiple devices // bring their own devices // change devices

Latest: 9618_s23_qp_13_sc_2.d

Question

Melinda mainly uses the internet to watch films and play games. Identify whether she should connect to the router using a wired or wireless network and justify your choice. (No mark for the identification.)

Answer — 5 points for 3 marks

• Wired: faster connection // higher bandwidth
• … needed as she is downloading / streaming large files
• … less time waiting / less latency / fewer delays
• More reliable / stable connection … less susceptible to issues with distance, walls or interference
• More secure

Latest: 9618_s21_qp_11_sc_4.c.ii. Wireless is also creditable: freedom of movement; no physical connection; easily expanded; less cabling and expertise so cheaper to set up.

Question

Give three benefits of fibre-optic cable over copper cable.

Answer — 5 points for 3 marks

• Less interference in the signal
• The signal does not degrade as fast // needs less signal boosting
• More secure // more difficult to hack or “tap” into
• Greater bandwidth // faster transmission speeds possible
• Lighter in weight, so easier to install // consumes less power

Latest: 9608_w18_qp_12_sc_2.c.i

Question

Give two drawbacks of fibre-optic cable over copper cable.

Answer — 6 points for 2 marks

• Initial installation cost is higher // cable / hardware is more expensive per metre
• Specialists / trained personnel are needed to install and maintain it
• Difficult to terminate // the electronics at both ends are more complex
• Fibre-optic cables can break when bent
• Only transmits data in one direction // cannot transmit power, only data
• If a fibre-optic connection fails, many more services can be affected

Latest: 9608_w18_qp_12_sc_2.c.ii

Question

State two benefits of copper cable over fibre-optic cable.

Answer — 4 points for 2 marks

• Copper cabling is less expensive to install
• Copper cable is easier to install because it is more flexible
• It is easier to make terminations using copper cabling
• Expertise in the use of copper cabling is more extensive / widely available

Latest: 9608_w15_qp_13_sc_6 (4 marks for both cable types combined, max 3 per type).

Question

Draw one or more lines from each communication medium (fibre-optic cable, radio waves, copper cable, satellite) to the appropriate feature(s).

Answer — 6 lines for 6 marks

• Fibre-optic cable → Transmits light pulses
• Fibre-optic cable → Least likely to have interference
• Radio waves → Large range of wavelengths
• Radio waves → Wireless transmission
• Copper cable → Can be twisted pair or co-axial
• Satellite → Wireless transmission

Latest: 9608_s18_qp_11_sc_1. 9608_s16_qp_13_sc_6.b adds: fibre optic is the fastest transmission medium; WiFi is radio waves.

Question

Describe two drawbacks of using a wireless network compared to a wired network. (2 marks each.)

Answer — 6 points for 4 marks

• Transmissions may be less secure … because data packets can be intercepted // easier connection by an unauthorised user
• Bandwidth may be limited // as more devices connect the bandwidth is reduced … so access may be slow
• It is subject to interference from other signals or obstacles … which can hinder transmission or corrupt data
• Limited range // greater attenuation … so there is a need for repeaters // users can easily move out of range
• Higher latency … so transmission will be slower
• The signal degrades quickly without repeaters or boosters

Latest: 9608_s21_qp_12_sc_9.b

Question

Describe two characteristics of microwave transmission.

Answer — 4 points for 2 marks

• Data is transmitted wirelessly as electromagnetic waves at high frequency
• A direct line of sight is needed between transmitter and receiver
• Used for point-to-point links over long distances
• Affected by weather and physical obstacles

Named in the syllabus notes but only ever accepted as an alternative to “radio waves”. Tariff set to 2.

Question

Give two advantages and two disadvantages of a wired network.

Answer — 6 points for 4 marks

• Advantage: fast data transfer
• Advantage: better physical security
• Advantage: high range (up to about 100 m) and less susceptible to interference
• Disadvantage: no portability — location is limited by the physical cable
• Disadvantage: cost — more cable is needed to add each new device
• Disadvantage: safety — cables are trip hazards and must be routed along walls or under floors

Tariff set to 4.

Question

Compare twisted pair, coaxial and fibre-optic cable.

Answer — 6 points for 4 marks

• Twisted pair carries electrical signals and is used for LAN connections in homes and offices; it is the cheapest and slowest, and is prone to electromagnetic interference
• Coaxial carries electrical signals and was used for telephone voice traffic and early internet infrastructure
• … coaxial degrades over time, limiting its range, and has lower bandwidth than fibre
• Fibre optic transmits light signals and is used for high-speed WANs and modern internet backbones
• … fibre has the highest bandwidth and speed, and suffers no interference, making it the most secure
• … fibre has minimal degradation so can span cities and countries, but is the most expensive

Tariff set to 4 to match the 9618 transmission-media table question.

---

2.1.8 Hardware used to support a LAN

Question

Describe the role of a switch in a network.

Answer — 5 points for 3 marks

• To store the MAC addresses of devices connected to it
• To receive packets from devices
• To forward packets directly to the intended recipient
• To provide a central point of connection for the network
• To enable connected devices to communicate

Latest: 9618_s25_qp_12_sc_6.e

Question

Complete the table by writing the purpose of each of these hardware devices used to support a LAN: switch, Wireless Access Point (WAP), bridge. (Max 1 mark each.)

Answer — 6 points for 3 marks

• Switch: to allow two or more devices to communicate with one another
• Switch: to receive transmissions and forward them to their destination
• WAP: to allow devices to connect to the central device using radio signals / Wi-Fi
• WAP: to allow wireless-enabled devices to connect to a wired network
• Bridge: to connect two LANs / segments with the same protocol
• Bridge: to transmit data between two networks with the same protocol

Latest: 9618_w23_qp_11_sc_2.b

Question

Describe the functions of a Wireless Network Interface Card.

Answer — 6 points for 4 marks

• Provides the interface to the wireless network … as an antenna
• Receives analogue radio waves … and converts them to digital / binary
• Checks incoming transmissions for the correct MAC / IP address … and ignores transmissions not intended for it
• Encrypts / encodes the data
• Decrypts / decodes the data
• Takes digital / binary input and converts it to analogue waves … then sends the radio waves via the antenna

Latest: 9618_w21_qp_11_sc_8.c

Question

Identify two possible devices that can be used to physically connect 30 computers to the rest of the network.

Answer — 3 points for 2 marks

• Router
• Switch
• Hub

Latest: 9618_w21_qp_11_sc_8.b

Question

A router is attached to one of the devices on the LAN to connect it to the internet. Identify the device and give a reason for your choice.

Answer — 4 points for 2 marks

• Device: Server … reason: the server processes the requests and authorises traffic // firewall software on the server authorises traffic // the server acts as the proxy
• Device: Switch … reason: the switch is connected to all the computers // to share access to the router on the network

Latest: 9618_w22_qp_12_sc_10.b.i

Question

Give two similarities and one difference between a router and a gateway.

Answer — 5 points for 3 marks

• Similarity: both devices regulate network traffic between two networks // both connect two networks
• Similarity: both receive packets from a network and both forward packets onto a network
• Similarity: both can assign private IP addresses
• Difference: a router connects two networks using the same protocol, whereas a gateway can connect two networks using different protocols
• Difference: a router operates between similar networks, a gateway between dissimilar networks

Latest: 9608_s20_qp_11_sc_8.c. 9608_s19_qp_12_sc_1.c marks “explain the role of routers and gateways” at 4 (max 3 each).

Question

Identify two pieces of hardware, other than the cables, that enable servers to connect to the internet. Describe the purpose of each device. (1 mark device + 1 mark purpose, max 2 devices.)

Answer — 6 points for 4 marks

• Router … to connect the servers to the internet // to forward data towards its destination
• Gateway … to connect a server that uses a different protocol to the internet // to join two different types of network
• Modem … to connect the servers to the internet over a telephone line
• NIC … to enable the servers to connect to the company network
• A router transmits data between the servers and the internet
• A NIC gives each server a MAC address identifying it on the network

Latest: 9608_s20_qp_12_sc_7.a

Question

Describe the function of a repeater in a network.

Answer — 4 points for 2 marks

• Receives a weak signal and retransmits it at full strength
• Boosts or regenerates the signal
• Extends the range of a wired or wireless network
• Allows data to travel long distances without loss of quality

Named in the syllabus notes; appears only as a mark point inside a wireless-drawback answer. Tariff set to 2.

Question

Describe the function of a Network Interface Card.

Answer — 4 points for 2 marks

• Enables a device to connect to a network, providing a dedicated full-time connection
• Converts the computer’s data into a format suitable for the network
• Sends and receives data packets between the computer and the network
• Has a unique MAC address that identifies the device on the network

Named in the syllabus notes and never examined. Tariff set to 2, matching the WAP/bridge table entries.

Question

Describe the role of the server in a LAN.

Answer — 5 points for 3 marks

• Provides services and resources to the client devices on the network
• Stores and manages files centrally
• Controls access to shared resources such as printers
• Handles multiple requests from clients at the same time
• Manages user accounts, access rights and central backup

Tariff set to 3 to match the switch question, 9618_s25_qp_12_sc_6.e.

Question

Give two differences between a switch and a hub.

Answer — 4 points for 2 marks

• A hub broadcasts data to every device on the network, whereas a switch forwards data only to the intended recipient
• A switch stores the MAC addresses of connected devices; a hub does not
• A hub creates more unnecessary network traffic than a switch
• A hub is less secure, because every device receives every packet

Tariff set to 2.

Question

Describe how a switch uses its lookup table.

Answer — 4 points for 2 marks

• The switch holds a lookup table that maps each port to a MAC address
• When a packet is received, the switch examines the destination MAC address
• It looks that address up in the table
• It forwards the packet out of the corresponding port only

Tariff set to 2. The port↔MAC table is not named in any mark scheme.

Question

Describe two functions of a bridge.

Answer — 4 points for 2 marks

• Connects two network segments so that two LANs act as one larger network
• Both networks must use the same protocol
• Filters traffic by checking MAC addresses to decide whether data should cross the bridge
• This reduces overall network traffic, as only necessary data is forwarded

Tariff set to 2. The filtering behaviour is not credited in the 9618 mark scheme.

---

2.1.9 Role and function of a router

Question

Describe the function of a router in a network.

Answer — 5 points for 3 marks

• Receives packets from the internet / external network
• Analyses the destination IP address of each packet
• Forwards the packet towards its destination … using the routing table
• Maintains / updates the routing table
• Allocates private IP addresses to devices on the LAN
• Finds the most efficient route to the destination

Latest: 9618_w23_qp_11_sc_2.a. Also creditable: implements a firewall; changes the packet format for transmission over the next network; performs NAT; acts as a gateway; provides the LAN with a public IP address; maintains a table of MAC and IP addresses.

Question

Describe the role of routers in the transmission of data through the internet.

Answer — 4 points for 2 marks

• Receives packets from the internet
• Analyses the destination IP address of each packet
• Forwards the packet towards its destination using the routing table
• Finds the most efficient route to the destination

Latest: 9618_s24_qp_12_sc_3.c.i

Question

Identify three functions of a router in a home network.

Answer — 5 points for 3 marks

• To receive packets from devices or the internet
• To forward / route packets to the destination
• To find the destination of the packet
• To assign / allocate private IP addresses to devices on the LAN
• To store / update / maintain a routing table // to find the most efficient path

Latest: 9618_w21_qp_12_sc_3.b.ii

Question

Tick one box in each row to identify whether the task is performed by the router or not.

Answer — 4 rows for 2 marks

• Receives packets from devices → Performed by router
• Finds the IP address of a URL → Not performed by router (that is DNS)
• Directs each packet to all devices attached to it → Not performed by router
• Stores the IP and/or MAC address of all devices attached to it → Performed by router

Latest: 9618_s21_qp_11_sc_4.c.i

Question

Explain how data is transmitted between two laptops in a LAN via the router.

Answer — 5 points for 2 marks

• The data from the sending laptop is transmitted to the router
• The data has the address of the recipient
• The router determines the recipient’s destination address
• … by using a routing table
• The router transmits data directly / only to the recipient

Latest: 9618_w23_qp_12_sc_7.b.ii

Question

Describe what a routing table contains and how a router uses it.

Answer — 5 points for 3 marks

• The routing table stores a list of known networks and the routes to them
• The router reads the destination IP address from the packet header
• It looks that address up in the routing table
• It determines the next network / device the packet should be sent to
• It forwards the packet along the most efficient route

Named in almost every router mark scheme but never the subject of a question. Tariff set to 3.

Question

Explain how NAT allows the devices on a LAN to communicate over the internet.

Answer — 4 points for 2 marks

• Each device on the LAN has a private IP address, which cannot be used on the internet
• The router has a single public IP address
• NAT translates the private address of a device into the router’s public address for outgoing traffic
• … and translates returning traffic back to the correct private address

Appears as an accepted mark point only. Tariff set to 2.

Question

Describe the structure of a packet and explain what is meant by a hop.

Answer — 5 points for 3 marks

• A packet consists of a header and a payload
• The header contains control information, including the sender’s and recipient’s IP addresses
• The payload is the actual data being sent
• The router reads the header to determine the destination
• Each pass from one router to the next is called a hop

Tariff set to 3. Neither “payload” nor “hop” appears in a mark scheme in this topic.

---

2.1.10 Ethernet and collisions

Question

Describe what is meant by Ethernet.

Answer — 6 points for 3 marks

• A protocol (suite)
• For data transmission over standard / universal wired / cabled network connections
• Uses Carrier Sense Multiple Access / Collision Detection (CSMA/CD)
• Data is transmitted in frames
• … each frame has a source and destination (IP/MAC) address
• … and error-checking data, so damaged frames can be resent

Latest: 9618_s23_qp_12_sc_1.d

Question

Describe how Carrier Sense Multiple Access / Collision Detection (CSMA/CD) is used in a bus network.

Answer — 7 points for 4 marks

• CSMA/CD is a protocol used to detect and prevent collisions in a bus topology
• Before transmitting, a device checks if the channel is busy
• If the channel is busy the device waits // if the channel is free the data is sent
• Because there is more than one computer connected to the same transmission medium …
• … two workstations can start to transmit at the same time, causing a collision
• If a collision is detected by the device, transmission is aborted / a jamming signal is transmitted
• Both devices wait a (different) random time and then try again

Latest: 9618_w22_qp_11_sc_8. 9618_w25_qp_12_sc_5.d adds: the random time is increased if there are multiple collisions.

Question

State three tasks performed by devices to deal with collisions when using CSMA/CD.

Answer — 6 points for 3 marks

• To monitor the communications channel
• To send data only when there is no data being transmitted / the line is idle
• To detect a collision and then stop transmission of further data // transmit a jamming signal
• To calculate a random wait time / back-off time
• … then retransmit the data after that random wait time
• Increase the random time if there are multiple collisions

Latest: 9618_w23_qp_12_sc_7.c

Question

Identify two drawbacks of using CSMA/CD.

Answer — 6 points for 2 marks

• The random time is increased each time, so waiting can be infinite
• There may be a constant jamming signal so nothing ever sends
• Certain nodes cannot be prioritised
• High power consumption
• Only suitable for a short-distance network // limited distance
• Not scalable // more nodes means exponentially longer waiting times

Latest: 9618_s24_qp_13_sc_5.c.ii

Question

Explain why collisions occur in a bus network but not in a star network that uses a switch.

Answer — 5 points for 3 marks

• In a bus network all devices share the same single transmission medium
• Two devices can begin transmitting at the same time
• … so their signals interfere, causing a collision
• In a star network each device has its own dedicated connection to the switch
• The switch forwards each packet only to the intended recipient, so transmissions do not interfere

Tariff set to 3. Only ever a sub-point inside 9618_w22_qp_11_sc_8.

Question

Describe the contents of an Ethernet frame.

Answer — 6 points for 4 marks

• Preamble — a sequence of bits used to synchronise communication between devices
• Destination MAC address — the unique ID of the device the data is being sent to
• Source MAC address — the unique ID of the device sending the data
• EtherType / Length — indicates the type of data or the size of the payload
• Payload — the actual data being sent
• FCS (Frame Check Sequence) — used for error detection, to check the data arrived correctly

Tariff set to 4: the 9618 mark scheme credits only “frames have addresses and error-checking data”, so a full-structure question would carry more marks.

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2.1.11 Bit streaming

Question

State what is meant by bit streaming.

Answer — 3 points for 1 mark

• A continuous, ordered flow of bits over a communication path
• The bits arrive in the same order as they were sent
• Data is sent in small chunks so it can be played back immediately

Latest: 9618_s24_qp_11_sc_2.e.i

Question

Explain how data is transferred using real-time bit streaming.

Answer — 6 points for 4 marks

• Video is transmitted continuously
• … as a series of bits
• The video is uploaded to a media server, and users download from it
• On download, the media server sends the data to a buffer on the user’s device
• The buffer is used when there is a difference in speed between transmission and receipt
• The recipient views the bit stream from the buffer

Latest: 9618_s25_qp_11_sc_2.a

Question

Give two differences between real-time and on-demand bit streaming.

Answer — 4 points for 2 marks

• Real-time is direct from source, whereas on-demand is pre-recorded / downloaded to view later
• Real-time cannot be re-watched; on-demand can be paused, re-watched, fast-forwarded
• Real-time plays continually; on-demand downloads sections and cannot play until the next section is downloaded
• Real-time needs a strong steady connection; on-demand can adjust quality to the connection

Latest: 9618_s24_qp_11_sc_2.e.ii

Question

Explain the reasons why a video is compressed before it is transmitted using real-time bit streaming.

Answer — 6 points for 4 marks

• Video is data-intensive
• The file size needs reducing in order to …
• … reduce the amount of bandwidth used
• … and reduce buffering
• This means people are not behind in the conversation
• … and people with lower bandwidth can still take part

Latest: 9618_s25_qp_11_sc_2.b.i

Question

Explain how bit streaming is used in a real-time video conference.

Answer — 6 points for 4 marks

• Data is compressed before transmitting
• The video and audio are transmitted continuously as a series of bits
• The video is uploaded to a media server
• On download, the media server sends the data to a buffer
• The buffer stores data from the server until the receiving device can process it
• The receiving device receives the bit stream from the buffer

Latest: 9618_w24_qp_13_sc_9.c

Question

A website uses on-demand bit streaming. Describe how it is possible to watch the video without it continually pausing.

Answer — 5 points for 4 marks

• The user needs a high-speed broadband connection
• Data is streamed to a buffer in the computer
• Buffering stops the video pausing as bits are streamed
• As the buffer is emptied, it fills up again so that viewing is continuous
• Actual playback is a few seconds behind the time the data is received by the computer

Latest: 9608_w16_qp_13_sc_6

Question

Give two benefits of using bit streaming to watch a film.

Answer — 4 points for 2 marks

• No need to wait for a whole file to be downloaded
• No need to store large files on the user’s computer
• Allows on-demand playback
• No specialist software is required for playback in a browser

Latest: 9608_w15_qp_13_sc_1.b.i

Question

State two potential problems of using bit streaming to watch a film.

Answer — 5 points for 2 marks

• Video stops / hangs if the internet or broadband speed is very slow
• Video stops / hangs if there is inadequate buffering capacity
• Loss of internet means the films / files cannot be accessed
• May require specific software to run the files
• Viruses can be downloaded from the websites

Latest: 9608_w15_qp_13_sc_1.b.ii

Question

Dominic records a video and sends it to colleagues over the internet using bit streaming. Circle whether the video is sent using real-time or on-demand bit streaming and justify your choice.

Answer — 3 points for 2 marks

• On-demand
• The video does not need to be broadcast live // the video is already recorded
• Dominic’s colleagues will watch the video at a later date / at their convenience

Latest: 9608_w19_qp_12_sc_6.e.ii

Question

Explain how bit rate and broadband speed affect bit streaming.

Answer — 6 points for 4 marks

• Bit rate is the amount of data transmitted in a given unit of time
• A higher bit rate allows higher-quality content, e.g. HD or 4K …
• … but uses more bandwidth and needs a larger buffer
• A lower bit rate produces pixelation and blurriness, especially in fast movement
• High-speed broadband supports higher bit rates, several devices streaming at once, and smooth playback with minimal buffering
• Slow broadband cannot sustain a high bit rate, forcing lower resolution and causing frequent buffering

Named explicitly in the syllabus notes and untested in either series. Tariff set to 4 to match the other 9618 bit-streaming “explain” questions.

Question

Explain what is meant by adaptive bitrate and why it is used.

Answer — 4 points for 2 marks

• The streaming platform adjusts the bit rate dynamically based on network performance
• If the connection slows, a lower bit rate is used
• … so playback continues without buffering, at reduced quality
• This allows on-demand streaming to cope with a variable connection, which real-time streaming cannot do as easily

Tariff set to 2. The term appears in no mark scheme.

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2.1.12 Differences between the WWW and the internet

Question

Melinda sends emails from her webmail account (an email account accessed through a website). Explain whether Melinda is using the internet, the WWW, or both.

Answer — 4 points for 3 marks

• She is using both
• Using the internet because she is sending data on the infrastructure
• Using the WWW because she is accessing a website …
• … that is stored on a web server operated by the webmail provider, and is part of the WWW

Latest: 9618_s21_qp_11_sc_4.d

Question

A student states, “The internet and the World Wide Web are the same thing”. Tick one box to indicate whether this is true or false, and justify your choice. (1 mark for the tick + max 4 for justification.)

Answer — 6 points for 5 marks

• False
• The internet is the infrastructure / global collection of networks
• The World Wide Web is the multimedia web pages / content
• The World Wide Web is accessed over the internet
• Web pages are written in HTML
• HTTP protocol is used to transfer web pages, whereas the internet uses the IP protocol

Latest: 9608_s18_qp_11_sc_5.b

Question

Distinguish between the internet and the World Wide Web. (Max 2 marks for internet references, max 2 for WWW references.)

Answer — 5 points for 3 marks

• Internet: a massive network of networks / interconnected network of computer devices
• Internet: “Internet” stands for Interconnected Networks, and it uses the TCP/IP protocol
• WWW: a collection of (multimedia) web pages / documents stored on websites
• WWW: HTTP protocols are used to transmit the data, and web pages are written in HTML
• WWW: URLs specify the location of web pages, and the documents are accessed using browsers

Latest: 9608_s15_qp_12_sc_5.b. 9608_s16_qp_13_sc_6.a is the 2-mark version.

Question

A user makes a voice call over the internet using an app. Explain whether they are using the internet, the WWW, or both.

Answer — 5 points for 3 marks

• The internet only
• The data travels on the internet infrastructure
• … using the TCP/IP protocol
• No website is accessed, so the WWW is not used
• The WWW is only the collection of web pages stored on web servers

Tariff set to 3 to match 9618_s21_qp_11_sc_4.d. Only one 9618 question exists in this whole bullet.

Question

Describe the relationship between the internet and the World Wide Web.

Answer — 4 points for 2 marks

• The internet is a global network of networks, and is the most well-known WAN
• It is the infrastructure that provides connectivity to the WWW, using TCP/IP
• The WWW is a collection of interconnected documents and multimedia files stored on web servers worldwide
• … retrieved and displayed by a web browser using HTTP / HTTPS

Tariff set to 2.

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2.1.13 Hardware used to support the internet

Question

Explain how data is transmitted using the cell phone network.

Answer — 6 points for 4 marks

• Land is split into cells designed for maximum line of sight
• Each cell has a tower with an antenna which receives and transmits data
• Data is transmitted between the tower and the phone
• Data transmission is wireless, using low-power radio signals / frequencies
• Multiple devices can communicate simultaneously with the same tower
• As a user moves, the device switches to the next closest tower

Latest: 9618_s25_qp_12_sc_6.b. The final point (handover) is SME content, not in the mark scheme.

Question

Complete the table by stating how modems and dedicated lines are used when data is transmitted over the internet.

Answer — 4 points for 2 marks

• Modems: converts digital data into analogue for transmission down phone lines
• Modems: converts analogue data into digital after transmission down phone lines
• Dedicated lines: used to provide a direct / private connection
• Dedicated lines: … which therefore provides faster transmission

Latest: 9618_s25_qp_11_sc_2.c

Question

Describe the role of the PSTN (Public Switched Telephone Network) in the transmission of data through the internet.

Answer — 4 points for 2 marks

• The PSTN consists of many different types of communication lines
• … therefore the digital data may need to be converted into a different form / analogue signal
• Data is transmitted in both directions at the same time // duplex data transmission
• Using a PSTN the communication passes through different switching centres / ISPs

Latest: 9618_s24_qp_12_sc_3.c.ii

Question

Identify one benefit and one drawback of installing a dedicated line between two buildings.

Answer — 5 points for 2 marks

• Benefit: (probably) faster connection / communication / transmission of data
• Benefit: (usually) more consistent transmission speed
• Benefit: improved security
• Drawback: expensive to set up / maintain
• Drawback: disruption to the dedicated line would leave no alternative route

Latest: 9608_s19_qp_12_sc_1.b.ii

Question

Put a tick in the correct column to match each description to conventional telephone using PSTN or an internet-based system.

Answer — 5 rows for 5 marks

• Connection only in use whilst sound is being transmitted → Internet-based
• Dedicated channel used between two points for the duration of the call → PSTN
• Connection maintained throughout the telephone call → PSTN
• Encoding schemes and compression technology used → Internet-based
• Lines remain active even during a power outage → PSTN

Latest: 9608_s15_qp_12_sc_5.a

Question

State the role of an Internet Service Provider.

Answer — 4 points for 2 marks

• Provides the customer with a connection to the internet
• Assigns a public IP address to the customer’s router
• Routes the customer’s traffic on towards its destination through its own switching centres
• May also provide services such as email and web hosting

Drawn in 9618_w22_qp_13_sc_7.a and named in the PSTN mark scheme, but never defined. Tariff set to 2.

Question

A company needs a high-security, high-speed link between two of its offices. Identify the most appropriate technology and justify your choice.

Answer — 5 points for 3 marks

• A dedicated line
• The connection is private / direct, so it is more secure
• It is always active and not shared with other users
• … so the transmission speed is faster and more consistent
• The PSTN would be slower because the data passes through shared switching centres

Tariff set to 3 to match 9618’s other “justify your choice” questions.

Question

Describe how a mobile device stays connected as the user moves, and name the generations of mobile technology.

Answer — 5 points for 3 marks

• The network is divided into cells, each served by a cell tower / base station
• The device connects to the nearest tower
• As the user moves, the device automatically switches to the next closest tower — this is called handover
• 2G supports basic calls and texts; 3G supports mobile internet and video calling
• 4G supports fast browsing and streaming; 5G supports very high speed and low latency

Tariff set to 3. Neither handover nor the generations appear in the mark scheme.

Question

Name two types of dedicated line and state a characteristic of each.

Answer — 4 points for 2 marks

• T1 line — up to about 1.54 Mbps
• T3 line — up to about 45 Mbps
• Fibre-optic — speeds in the gigabits
• All are always active and not shared with other users, unlike the PSTN

Tariff set to 2.

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2.1.14 IP addresses

Format of an IP address (IPv4 and IPv6)

Question

Complete the description of IP addresses by writing the missing words.

Answer — 6 gaps for 6 marks

• IPv4 is made of four groups of 8-bit numbers separated by full stops. Each IPv4 address is 32 bits.
• IPv6 is made of eight groups of 4 hexadecimal numbers separated by colons.
• Multiple consecutive groups of zeros can be replaced with a double colon.
• Each IPv6 address is 128 bits.
• A dynamic IP address can change each time the computer connects to a network.
• A private IP address can only be accessed by other devices in the same LAN and is assigned by the router within the LAN.

Latest: 9618_s25_qp_12_sc_6.c. 9618_s23_qp_11_sc_4.d.i is the 5-mark version: IPv4 has 4 groups of 8 bits; IPv6 has 8 groups of 16 bits; groups of zeros are replaced with a double colon.

Question

One difference between IPv4 and IPv6 is that the numbers in IPv4 are separated by full stops and in IPv6 by colons. Identify two other differences.

Answer — 4 points for 2 marks

• IPv4 has 4 groups of digits whilst IPv6 has 8 groups
• IPv4 is usually represented in denary whilst IPv6 is usually represented in hexadecimal
• IPv4 groups are between 0 and 255 whilst IPv6 groups are between 0 and FFFF
• IPv4 is 32 bits whilst IPv6 is 128 bits

Latest: 9618_s24_qp_11_sc_8.b.ii

Question

Consider the IP address 256.0.0.A. Circle whether it is IPv4, IPv6 or invalid, and justify your choice. (No mark for the choice.)

Answer — 4 points for 2 marks

• It is invalid
• It is not IPv4 because the maximum denary value should be 255, and this uses 256
• It is not IPv6 because it uses a full stop to separate sections and not a colon
• // It is not IPv6 because there are not enough groups

Latest: 9618_w25_qp_11_sc_7.b. 9618_w23_qp_12_sc_7.a adds: it is a 32-bit / 4-byte address whereas IPv6 is 128 bits / 16 bytes.

Question

Put one tick in each row to identify the minimum number of bits used to store each example of data.

Answer — 6 rows for 3 marks (3 marks for 6 correct, 2 for 4–5, 1 for 2–3)

• The hexadecimal value F139 → 16
• 16 000 000 unique amplitude values → 24
• An IPv4 address → 32
• 256 unique colours → 8
• An IPv6 address → 128
• The denary value 65 000 → 16

Latest: 9618_w25_qp_13_sc_2.a

Question

Describe the format of an IP address.

Answer — 5 points for 3 marks (IPv4 or IPv6)

• IPv4: four groups of denary or hexadecimal integers, separated by full stops
• IPv4: numbers between 0 and 255 / 0 and FF
• IPv4: each group stored in 1 byte / 8 bits; the whole address in 32 bits / 4 bytes
• IPv6: eight groups of hexadecimal digits separated by colons, between 0 and FFFF
• IPv6: each group stored in 2 bytes / 16 bits; the whole address in 128 bits / 16 bytes; the first instance of multiple groups of zero can be replaced by a double colon

Latest: 9608_w21_qp_11_sc_11.b. A correct example also earns a mark.

Question

For each IP address, indicate whether it is valid or invalid and give a reason. (1 mark per correct combination of judgement and reason.)

Answer — 4 addresses for 4 marks

• 3.2A.6AA.BBBB (hex) → Invalid: this is more than 32 bits // 6AA / BBBB is bigger than FF / 255 // uses more than 8 bits per group
• 2.0.255.1 (denary) → Valid: there are 4 bytes, each 255 or below // all values are in the range 0–255
• 6.0.257.6 (denary) → Invalid: 257 is above 255 // the third group is above 255
• 0A.78.F4.J8 (hex) → Invalid: J is not a valid hexadecimal digit
• IPv6 variants: 56FE::2159:5BBC::6594 → Invalid: only one double colon is allowed
• IPv6 variants: 15EF:5L63::2014:BB::60AA → Invalid: L is not a valid hexadecimal number

Latest: 9608_s16_qp_12_sc_7.b; IPv6 examples from 9608_w18_qp_11_sc_2.b.i and 9608_w18_qp_13_sc_4.b.ii.

Question

State why there is a need for IPv6 addressing.

Answer — 3 points for 1 mark

• The number of IP addresses needed will exceed the number available using IPv4
• IPv4 provides only about 4 billion addresses (2³²)
• IPv6 provides 2¹²⁸ addresses, enough for every device

Latest: 9608_s19_qp_12_sc_1.a.ii. The figures are SME content, not in the mark scheme.

Question

Describe the purpose of an IP address.

Answer — 4 points for 2 marks

• IP stands for Internet Protocol
• Gives each device on a network an identifier // an IP address is used to locate a device on a network
• Each address is unique within the network
• Allows a device / gateway / node to send data to the correct destination

Latest: 9608_w18_qp_12_sc_2.b; “Internet Protocol” from 9608_s16_qp_12_sc_7.a.

Question

Rewrite the IPv6 address 2001:0db8:0000:0000:0000:ff00:0042:8329 in its shortened form and explain the rule you used.

Answer — 4 points for 2 marks

• 2001:0db8::ff00:0042:8329
• Multiple consecutive groups that contain only zeros are replaced with a double colon
• Only one double colon may be used in an address
• … because otherwise it would be ambiguous how many zero groups each one represents

Both series only describe the rule. Tariff set to 2, matching the other IPv6-format questions.

Subnetting

Question

Describe the purpose of subnetting in a network.

Answer — 5 points for 2 marks

• It allows the network to be divided into smaller networks
• … which reduces traffic in some parts of the network // reduces congestion
• … because traffic only travels through the parts necessary
• … which hides the complexity of the network
• … and allows for easier maintenance of the network

Latest: 9618_w24_qp_13_sc_9.d.ii

Question

Describe two reasons why subnetting is used in a network. (1 mark per use + 1 mark per corresponding expansion.)

Answer — 6 points for 4 marks

• To improve the security of the LAN … so that devices do not receive unintended data
• … so that a compromised device does not expose the whole network
• To make network management easier … because faults can be isolated more efficiently
• To make the network easier to expand // for better control of network growth … by allowing a greater range of IP addresses to be available
• To improve network performance // to reduce network congestion … by localising network communications
• … because data sent between devices on the same subnet stays within the subnet

Latest: 9618_w23_qp_12_sc_7.b.iii

Question

An IP address in a subnetwork is divided into two parts. Identify and describe the two parts. (1 mark identification + max 2 description.)

Answer — 5 points for 3 marks

• An IP address is made up of a network ID and a host ID
• Each device in a subnetwork has the same network ID // each subnetwork has a different network ID
• Every device in each subnetwork has a different host ID but the same network ID
• The host ID uniquely identifies the device within the subnetwork
• The subnet mask is used to separate the two parts

Latest: 9618_s23_qp_13_sc_2.e

Question

Given 10.10.12.1 with mask 255.0.0.0, and 192.168.12.4 with mask 255.255.255.0, identify the network ID of the first and the host ID of the second.

Answer — 2 points for 2 marks

• Network ID for 10.10.12.1 = 10
• Host ID for 192.168.12.4 = 4
• Method: the parts of the address covered by 255s in the mask are the network ID; the parts covered by 0s are the host ID

Latest: 9618_w22_qp_13_sc_7.c.ii

Question

Give two drawbacks of subnetting a network.

Answer — 4 points for 2 marks

• Subnetting requires planning and technical expertise to set up
• Addresses are reserved for each subnet, so some IP addresses are wasted
• Additional hardware such as a router is needed to route traffic between subnets
• Communication between devices on different subnets is slower, as it must pass through a router

Benefits have been examined at least four times; the inverse never has. Tariff set to 2.

Public, private, static and dynamic

Question

Complete the table by writing the missing types of IP address and the missing descriptions.

Answer — 4 cells for 4 marks

• Public IP address — an IP address that is assigned to a device to allow direct access on the internet
• Static IP address — an IP address that is fixed / does not change each time a device re-joins a LAN or network
• Private IP address — an IP address used for internal LAN communication only
• Dynamic IP address — an IP address that may be refreshed / changed each time a device re-joins a LAN or network

Latest: 9618_w23_qp_12_sc_7.d. 9618_w25_qp_11_sc_7.a is the 2-mark version (static and public only).

Question

The router has a public IP address and a private IP address. State the purpose of each.

Answer — 4 points for 2 marks

• Public: so that the router is visible to the internet / external network / WAN
• Public: so that other devices on the internet can access it
• Private: so that the router is identified to computers within the LAN
• Private: it cannot be seen or used from outside the LAN

Latest: 9618_w24_qp_13_sc_9.d.i; “to be visible to and accessible by other devices on the internet” from 9618_s24_qp_11_sc_8.b.i.

Question

State what is meant by a static private IP address.

Answer — 3 points for 1 mark

• Static means the IP for that device does not change
• and private means it can only be accessed / seen / used within the LAN
• Both halves are needed for the mark

Latest: 9618_s24_qp_13_sc_5.d

Question

Draw one line from each term to its most appropriate description.

Answer — 4 lines for 4 marks

• Public IP address → It is visible to any device on the internet
• Private IP address → It is only visible to devices within the Local Area Network (LAN)
• Dynamic IP address → A new one is reallocated each time a device connects to the internet
• Static IP address → It does not change each time a device connects to the internet
• Distractors (unused): “It increments by 1 each time the device connects”; “It can only be allocated to a router”

Latest: 9618_s21_qp_12_sc_5.d

Question

Identify two differences between a public IP address and a private IP address.

Answer — 5 points for 2 marks

• A private IP is only known within the LAN // a public IP is known outside the LAN / on the internet
• A public IP is allocated by the ISP // a private IP is allocated by the router
• Public addresses are unique throughout the internet; private addresses are unique only within the LAN
• Private IP addresses are more secure than public IP addresses
• NAT is necessary for a private IP address to access the internet directly

Latest: 9608_s21_qp_11_sc_9.a. 9608_s16_qp_12_sc_7.c adds the private ranges: 10.0.0.1–10.255.255.254, 172.16.0.1–172.31.255.254, 192.168.0.1–192.168.255.254.

Question

Each computer in the network has a private IP address. Give two reasons why the computers do not have public IP addresses.

Answer — 4 points for 2 marks

• Improved security, because the IP address is not visible outside the network
• An internet presence is not required for each employee computer
• Only the router needs a public IP address, as only the router needs to be externally visible
• Reduces the number of public IP addresses needed

Latest: 9608_s20_qp_13_sc_1.c

Question

Tick one box in each row to identify whether each description applies to a public or a private IP address.

Answer — 4 rows for 4 marks

• The address can be reached over the internet → Public
• The address is more secure → Private
• The address can only be accessed through the same LAN → Private
• The address can be duplicated in different networks → Private
• From 9608_w18_qp_11_sc_2.b.ii: 192.168.2.1 is an example → Private; assigned by the ISP → Public; cannot be duplicated in different networks → Public; NAT is necessary to access the internet directly → Private

Latest: 9608_w18_qp_13_sc_4.c

Question

Explain why a web server would be given a static IP address rather than a dynamic one.

Answer — 4 points for 2 marks

• A static address does not change, so the server can always be found at the same address
• Other devices and DNS records rely on that address staying the same
• A dynamic address changes each time the device connects, so the server could not be reliably located
• Dynamic addresses are used for devices that do not need to be found, such as laptops and phones, and conserve the pool of addresses

Named in the syllabus notes (“difference between a static IP address and a dynamic IP address”) but never asked as a reason. Tariff set to 2.

Question

Explain why using private IP addresses within a LAN improves security.

Answer — 4 points for 2 marks

• Private addresses are not routable on the internet
• … so devices on the LAN are not directly visible or reachable from outside
• An attacker on the internet cannot address an individual LAN device directly
• Only the router, with its single public address, is exposed to the internet

The syllabus notes say “…and the implications for security”. Tariff set to 2.

Question

State the type of device that would be given a public IP address and the type that would be given a private IP address.

Answer — 4 points for 2 marks

• Public: devices needing a constant internet presence, e.g. web servers and email servers
• … these are globally unique and directly reachable from anywhere on the internet
• Private: devices on a LAN assigned by the router, e.g. laptops, phones and printers
• … these are not routable on the internet, which improves security

Tariff set to 2.

Question

State the protocol that automatically allocates dynamic IP addresses.

Answer — 3 points for 1 mark

• DHCP (Dynamic Host Configuration Protocol)
• It allocates addresses automatically from a pool of available addresses
• Caution: DHCP is not named in the 9618 syllabus and appears in no mark scheme in either series. In an exam, answer in the syllabus’s own words — “assigned by the router”, “changes each time the device connects”.

Tariff set to 1.

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2.1.15 URLs and the DNS

Question

A user types a URL into the address bar of a web browser. Explain how the web browser uses the URL to access the web page.

Answer — 8 points for 4 marks

• The browser checks its cache for the URL
• The browser parses the URL and splits it into its component parts
• The browser finds the IP address for the domain name by querying a DNS server
• The browser receives the matching IP address from the DNS server
• The browser creates a connection with the web server with the matching IP address
• A request for the resource is sent to the web server with that IP address
• The browser renders and displays the result
• The IP address is stored in the browser cache for future use

Latest: 9618_w25_qp_11_sc_7.c — the only 9618 question in this whole bullet.

Question

Describe how a URL is converted into its matching IP address.

Answer — 6 points for 3 marks

• The URL is parsed to obtain the domain name
• The domain name is sent to the nearest Domain Name Server (DNS)
• The DNS holds a list of domain names and matching IP addresses
• The DNS name resolver searches its database for the domain name
• If the domain name is found, the IP address is returned to the originator
• If it is not found, the request is forwarded to a higher-level DNS; if it is finally not found, an error message is generated

Latest: 9608_s19_qp_11_sc_1.b. 9608_s16_qp_13_sc_6.e is the 4-mark version, adding: the original DNS server adds the returned IP address to its cache.

Question

An employee states, “A domain name and an IP address are exactly the same thing”. State whether this is true or false and justify your choice.

Answer — 5 points for 3 marks

• False
• The IP address is the (physical) address of the server
• A domain name is a memorable form for an IP address, and each domain name is linked to an IP address
• A DNS is used to translate a domain name into its corresponding IP address
• The domain name does not change, but the IP address could change (dynamic)

Latest: 9608_s21_qp_13_sc_6.b

Question

For the URL http://cie.org.uk/computerscience.html, give the meaning of each part.

Answer — 3 parts for 3 marks

• http — enables the browser to know what protocol is being used to access the information in the domain
• cie.org.uk — the domain name (the name of the server where the resource is located)
• computerscience.html — the actual web page / file being viewed

Latest: 9608_w15_qp_13_sc_3.b.i

Question

Describe the function of the characters %20 and ? when they appear in a URL.

Answer — 3 points for 2 marks

• %20 — a space is not allowed in a URL, so %20 is the coding for a space
• … 32 in denary
• ? — separates the URL from all parameters or variables

Latest: 9608_w15_qp_13_sc_3.b.ii

Question

Complete the sequence of steps that take place when a user types a URL into a browser. (1 mark for one letter correct, 2 marks for all three.)

Answer — 5 steps for 2 marks

1. The user types the URL into the web browser
2. The web browser sends the URL to the Domain Name Service (DNS)
3. The DNS looks up the URL in a table
4. The DNS finds the corresponding IP address
5. The DNS returns the IP address to the web browser

Latest: 9608_w18_qp_12_sc_2.a

Question

State how a computer could access a web page without using a Domain Name Service (DNS).

Answer — 2 points for 1 mark

• Use the IP address instead of the URL
• Type the IP address directly into the browser’s address bar

Latest: 9608_w18_qp_11_sc_2.a

Question

Explain why the browser and the DNS server store IP addresses in a cache.

Answer — 4 points for 2 marks

• So that the IP address does not have to be looked up again next time
• … which makes the page load faster
• It reduces the number of requests sent to DNS servers
• … which reduces traffic on the network

Credited as a mark point in 9618_w25_qp_11_sc_7.c but never explained. Tariff set to 2.

Question

Describe what happens when the nearest DNS server cannot find the domain name.

Answer — 5 points for 3 marks

• The request is passed on to a higher-level DNS server
• A root server is contacted, which points to the correct Top-Level Domain (TLD) server, e.g. .com, .org
• The TLD server points to the authoritative DNS server for that domain
• The authoritative DNS server responds with the correct IP address
• The original DNS server caches the returned address for future requests
• Caution: the terms root server, TLD server and authoritative server appear in no mark scheme in either series. A 9618 answer needs only “passed to a higher-level DNS”.

Tariff set to 3.

Question

State what is meant by DNS propagation and explain when it is needed.

Answer — 4 points for 2 marks

• When a domain is registered, or its server’s IP address changes, the DNS records must be updated
• The spread of that update across the internet’s DNS servers is called DNS propagation
• It takes time, because each DNS server must receive the new record
• Until it completes, some users may still be directed to the old IP address

Named nowhere in the syllabus or the mark schemes. Tariff set to 2.

Question

State what is meant by a URL and identify its three parts.

Answer — 5 points for 3 marks

• A Uniform Resource Locator is a unique identifier for a web page — the website address
• It is text-based so that it is easy for people to remember
• Protocol — the communication method used to transfer data between client and server
• Domain name — the name of the server where the resource is located
• Web page / file name — the location of the file or resource on that server

Tariff set to 3, matching the 9608 URL-parts question.