What does the networks part of OCR section 1.3 cover?

It covers networks (LAN and WAN, topologies, client-server and peer-to-peer), network hardware (NIC, switch, router, wireless access point), protocols and layering with the TCP/IP four-layer stack and packet switching, the structure of the internet with the Domain Name System, URLs and IP and MAC addressing, network security threats and protective measures, and web technologies including HTML, CSS, JavaScript, client-side versus server-side processing and search engine indexing with PageRank.

What are the four layers of the TCP/IP stack?

The application layer provides services to user programs and chooses the protocol such as HTTP, FTP or SMTP. The transport layer (TCP) splits data into numbered segments, manages reliable delivery and reassembly, and uses ports. The internet layer (IP) adds source and destination IP addresses and routes packets between networks. The link layer handles the physical transmission on the local network using MAC addresses. Layering lets any layer be changed independently.

What is the difference between an IP address and a MAC address?

An IP address is a logical, routable address used at the internet layer to route packets between networks; it can change, for example when a device joins a new network. A MAC address is a physical address built into the network interface card by the manufacturer and is normally fixed, used at the link layer so a switch can deliver a frame to the right device on the local network.

How does a search engine rank pages?

Web crawlers follow hyperlinks from page to page, retrieving content and building a searchable index that maps keywords to pages. Results are then ordered by relevance to the query combined with importance. The PageRank algorithm judges importance from links: a link from one page to another is a vote, a page with many incoming links is more important, and a link from an already-important page carries more weight.

How should I revise the networks part of section 1.3?

Learn the TCP/IP layers in order with what each adds, and practise tracing data down and up the stack. Drill the distinctions OCR tests: switch versus router, IP versus MAC, internet versus web, client-side versus server-side, virus versus worm versus trojan, and firewall versus encryption. Be able to describe DNS resolution and how HTML, CSS and JavaScript divide structure, style and behaviour.

EnglandComputer Science

OCR A-Level Computer Science Networks and web technologies: TCP/IP, DNS and the web made exam-ready

A deep-dive OCR H446 guide to the networks part of Component 01 section 1.3, exchanging data. Covers network types, hardware, protocols and the TCP/IP stack, the structure of the internet with DNS and addressing, network security threats and protections, and web technologies including HTML, CSS, JavaScript and search engine ranking.

Generated by Claude Opus 4.815 min readH446 1.3Updated 2026-06-02

Reviewed by: AI editorial process; not yet individually human-reviewed

Jump to a section

What this section actually demands
Networks, protocols and the internet
Security and the web
How this section is examined
Check your knowledge

What this section actually demands

The networks half of section 1.3 is heavy on precise distinctions and on tracing how data and requests move. OCR rewards exact definitions (switch versus router, IP versus MAC, internet versus web), the ability to describe the TCP/IP layers and DNS resolution, and applied reasoning about security and where web processing belongs.

This guide walks through the topics in order and sets out the exam patterns OCR repeats. Each topic has a matching dot-point page with practice; this overview ties them together.

Networks, protocols and the internet

Network hardware, protocols and the TCP/IP stack covers LANs and WANs, topologies, client-server versus peer-to-peer, the hardware (NIC, switch, router, WAP), protocol layering, the four TCP/IP layers, and packet switching. The recurring skills are describing each layer and choosing client-server or peer-to-peer for a scenario.

The internet, DNS and web technologies covers the internet-versus-web distinction, URLs, DNS resolution, IP versus MAC addressing, and the web protocols (HTTP, HTTPS, FTP) in the client-server model. The classic questions are "describe the role of DNS" and "IP versus MAC".

Security and the web

Network security and protection covers malware (virus, worm, trojan), social engineering, attacks (SQL injection, denial of service, interception), and the defences of firewalls, proxies, encryption and access control, set as distinction and "how do these protect a network" questions.

HTML, CSS, JavaScript and web development covers the three web technologies, client-side versus server-side processing, and search engine crawling and PageRank, set as "roles of HTML, CSS, JavaScript" and "how a search engine works" questions.

How this section is examined

A typical OCR profile for the networks part of section 1.3:

Layer and trace questions. Describe the TCP/IP layers; trace a request through them; explain packet switching.
Distinction questions. Switch versus router, IP versus MAC, internet versus web, virus versus worm versus trojan, client-side versus server-side.
Security application. How firewalls, proxies and encryption protect a network, and why several are combined.
Web roles and ranking. HTML/CSS/JavaScript responsibilities; crawlers and PageRank.

Check your knowledge

A mix of recall and applied questions covering the section. Attempt them under timed conditions, then check against the solutions.

State which network hardware forwards packets between different networks. (1 mark)
State which TCP/IP layer is responsible for reliable delivery and reassembly. (1 mark)
Explain why DNS is needed. (2 marks)
State how a trojan differs from a worm. (2 marks)
State the role of JavaScript in a web page. (1 mark)
State what a web crawler does. (1 mark)

Solutions

Q1: A router (it forwards packets between networks using IP addresses); a switch forwards frames within a LAN using MAC addresses.
Q2: The transport layer (TCP), which splits data into numbered segments and manages reliable delivery, reassembly and ports.
Q3: People remember domain names more easily than numeric IP addresses, and the IP address can change while the name stays the same, so DNS provides the name-to-address lookup.
Q4: A trojan is disguised as legitimate software that the user installs and does not self-replicate; a worm self-replicates and spreads automatically across a network without user action.
Q5: To add client-side behaviour and interactivity in the browser, such as validating a form or updating part of a page without reloading.
Q6: It automatically follows hyperlinks from page to page, retrieving content and adding it to the search engine's index.

Sources & how we know this

OCR AS and A Level Computer Science (H046, H446) specification — OCR (2015)