The Internet & Protocols (Years 7–11) — Computer Science

How data crosses the internet: packets, the TCP/IP protocols, DNS name lookups, HTTP/HTTPS and the idea of protocol layers.

When you open a web page, your request is chopped into tiny packets, flung across the world through dozens of machines you'll never see, and reassembled in the right order on the far side — all in a fraction of a second. The rules that make this reliable are called protocols, and the internet is really just a giant agreement to follow them.

Why this matters: The internet works because every device, whatever its make, obeys the same protocols. Understanding TCP/IP, DNS and HTTPS explains how a message reaches exactly the right computer, why it arrives intact, and how you can tell a secure site from a risky one.

A packet carries a header (addresses + order number) and the payload (the actual data).

Packets and TCP/IP

TCP numbers the packets so they rebuild in order, even if routed apart.

Data is split into packets, each carrying a header (the source and destination IP addresses and a sequence number) and a payload (a slice of the actual data). Two protocols do the heavy lifting. IP (Internet Protocol) handles addressing and routing — getting each packet to the right machine. TCP (Transmission Control Protocol) handles reliability — splitting the data, numbering packets, checking none are missing, and reassembling them in order. Picture posting a long book one page at a time in numbered envelopes: IP writes the address, TCP numbers the pages so they can be rebuilt correctly even if they arrive out of order.

DNS: the internet's phone book

DNS turns a name you type into the IP address the network routes to.

People remember names like triomatic.co.uk, but computers route using numeric IP addresses. The DNS (Domain Name System) translates one into the other. When you type a web address, your device asks a DNS server, "What is the IP for this name?" and gets a number back before the request is sent. It is exactly like looking up a contact's name to find their phone number.

HTTP, HTTPS and layers

Each layer does one job and hands work to the layer below.

HTTP is the protocol for requesting and sending web pages. HTTPS is the same, but encrypted — the padlock in the address bar means data is scrambled so eavesdroppers can't read your passwords or card details. Protocols are organised into layers, each doing one job and passing work to the next, so designers can improve one layer without rewriting the rest.

Protocol	Job
TCP	Splits data, checks and reorders packets
IP	Addresses and routes packets
DNS	Turns a domain name into an IP address
HTTP / HTTPS	Requests web pages (HTTPS is encrypted)

Worked scenario: You visit https://bank.example. (1) DNS turns the name into an IP address. (2) TCP/IP splits your request into packets and routes them to that IP. (3) Because it's HTTPS, the data is encrypted in transit. (4) The reply arrives as packets, TCP reassembles them in order, and your browser displays the page.

Common mistake: Saying TCP finds the address and IP checks the data — it's the other way round. IP = addressing/routing; TCP = reliability/reassembly. A handy hint: IP and address both start with the idea of location.

Tip: Before entering a password or card number, check for https and the padlock. Plain http sends everything as readable text that anyone on the network could capture.