Networking and the Internet
Networking and the Internet is the A Level Computer Science topic covering how devices communicate over local networks and the wider internet: network hardware (hubs, switches, routers, wireless access points), network topologies (star, bus, mesh), the client-server and peer-to-peer models, the layers of the TCP/IP protocol stack, key application protocols (HTTP/HTTPS, FTP, SMTP, DNS), IP addressing (IPv4 and IPv6) and packet switching. It underpins how networked services, including client-server databases and the web, actually move data between machines.
Before you start
Make sure you're comfortable with these topics first:
Method
- Recall the four layers of the TCP/IP stack (application, transport, internet, link), then identify which protocol operates at each layer for a given scenario, e.g. HTTP/HTTPS and FTP at the application layer, TCP or UDP at the transport layer, IP at the internet layer.
- Choose between TCP and UDP for a scenario by weighing TCP's reliability (acknowledgements, retransmission of lost packets, delivery in order) against UDP's lower overhead and speed, matching the choice to whether the application needs perfect delivery or low latency.
- Distinguish packet switching (data is split into packets that are routed independently and reassembled at the destination) from circuit switching (a dedicated path is reserved for the whole communication), and explain why packet switching makes more efficient use of a shared network.
- Compare network hardware by what it forwards data on the basis of: a hub broadcasts to every connected port, a switch forwards a frame only to the port matching the destination MAC address, and a router forwards packets between different networks based on the destination IP address.
- Compare network topologies (star, bus, mesh) on cost, ease of adding a device, and what happens to the rest of the network if one cable or device fails.
- Compare the client-server and peer-to-peer network models on where resources are stored, who manages security and backups, and what happens if the server (or an individual peer) becomes unavailable.
- For a data-transfer calculation, convert the file size and the bandwidth to the same unit, typically bits, before dividing the data size by the bandwidth to find the transfer time.
Worked example
A user is downloading a file of size 45 megabytes (MB) over a broadband connection with a bandwidth of 20 megabits per second (Mbps). Calculate how long the download will take, giving your answer in seconds.
- Notice that the units do not match: the file size is in megabytes (MB) but the bandwidth is in megabits per second (Mbps), so convert one to match the other.
- Convert the file size from megabytes to megabits: there are 8 bits in a byte, so 45 MB = 45 x 8 = 360 megabits (Mb).
- Divide the file size in megabits by the bandwidth to find the time taken: 360 Mb / 20 Mbps.
- Calculate the result: 360 / 20 = 18.
- Final answer: the download will take 18 seconds, assuming the full 20 Mbps of bandwidth is available for the whole download.
Practice questions
Type your answer and press Check to be marked straight away, or reveal the answer and mark yourself.
Q1State what the acronym 'URL' stands for.Show answer
Answer: Uniform Resource Locator.
Q2Define the term 'protocol' in the context of computer networks.Show answer
Answer: An agreed set of rules that governs how devices communicate and exchange data on a network, covering things such as the format of the data, timing, sequencing and how errors are handled.
Q3A network has a bandwidth of 8 megabits per second (Mbps). Calculate how many seconds it would take to transfer a 4 megabyte (MB) file.Show answer
Answer: Convert 4 MB to megabits: 4 x 8 = 32 Mb. Time = 32 Mb / 8 Mbps = 4 seconds.
Q4State whether TCP or UDP would be more appropriate for a live video call, and give one reason for your choice.Show answer
Answer: UDP, because it has lower overhead and latency than TCP (it does not wait for acknowledgements or retransmit lost packets), which matters more for a live call than perfect reliability; a few dropped packets cause only a brief glitch rather than the whole call stalling while data is resent.
Q5Explain why a switch is generally more efficient than a hub for sharing data on a local area network (LAN).Show answer
Answer: A switch reads the destination MAC address of each frame and forwards it only to the port the destination device is connected to. A hub broadcasts every frame to all connected ports regardless of destination, which wastes bandwidth on the other ports and increases the chance of data collisions.
Q6State the purpose of DNS (the Domain Name System).Show answer
Answer: To translate a human-readable domain name, such as www.example.com, into the numeric IP address needed to route data to the correct server.
Q7State one advantage and one disadvantage of a star network topology compared with a bus topology.Show answer
Answer: Advantage: if one cable or device fails, the rest of the network is unaffected, because each device has its own dedicated cable back to the central switch. Disadvantage: if the central switch fails, the entire network goes down, and a star topology needs more cabling overall than a bus topology.
Q8Explain why IPv6 was introduced, given that IPv4 already existed.Show answer
Answer: IPv4 uses 32-bit addresses, giving only about 4.3 billion unique addresses (2^32), which is not enough for the number of internet-connected devices in use today. IPv6 uses 128-bit addresses, giving a vastly larger address space so that every device can still be given a unique address.
Exam-style questions
Written in the style of a A Level Computer Science exam paper, with a full mark scheme.
Describe how packet switching is used to send a file across the internet from one computer to another.
Show mark scheme
Tick each line you got. Your score builds from the marks on the scheme.
Nothing ticked yet - 4 available
A small design studio with 6 employees is deciding between a peer-to-peer network and a client-server network for sharing files and a printer. Explain two factors the studio should consider when making this decision.
Show mark scheme
Tick each line you got. Your score builds from the marks on the scheme.
Nothing ticked yet - 6 available
A secondary school is planning to move from a wired LAN to a wireless network (WLAN) across its campus, using several wireless access points connected back to a central switch. Evaluate this proposal.
Show mark scheme
Tick each line you got. Your score builds from the marks on the scheme.
Nothing ticked yet - 9 available
See real A Level Computer Science past-paper questions, with official mark schemes →
Free printable worksheet
Want more practice on paper? Download the networking and the internet worksheet pack - 14 pages of exam-style questions with a full mark scheme. One email opens every download in this browser for 14 days - no account, no card. Print it for personal and classroom use.
Next topics
Not quite what you needed?
Tell us what is missing on networking and the internet, or which topic to write up next. Every request is read, and we reply to every one.
Build a full practice pack.
This topic is one of hundreds in the library - pick the ones a student needs and generate a printable PDF in minutes.