A protocol is a set of rules that define how data is transmitted, formatted, and received between devices. Protocols allow devices made by different manufacturers to communicate — they are essential for interoperability.
TCP/IP: the fundamental suite used on the internet. TCP breaks data into packets, ensures they arrive correctly; IP addresses and routes packets between networks.
UDP: faster than TCP but no delivery guarantee — used for video streaming, gaming, VoIP where speed matters more than accuracy
Web & File Protocols
HTTP, HTTPS, FTP
HTTP (HyperText Transfer Protocol): transfers web pages from server to browser. Unencrypted — data visible to interceptors.
HTTPS: HTTP + SSL/TLS encryption. Data is encrypted in transit — secure for passwords, banking, shopping. Look for padlock icon in browser.
FTP (File Transfer Protocol): transfers files between computers. Used by web developers to upload files to servers. FTP is unencrypted; SFTP/FTPS add security.
DNS & DHCP
Address Management Protocols
DNS (Domain Name System): translates domain names (e.g. cszone.co.uk) into IP addresses (e.g. 192.168.1.1). Like a phone book for the internet — without DNS you'd have to remember every IP address.
DHCP (Dynamic Host Configuration Protocol): automatically assigns IP addresses to devices when they join a network. Prevents IP address conflicts and simplifies network management.
Exam Practice
Have a go at this question
Edexcel-style question
Explain the purpose of DNS and state why it is needed.
3 marks
DNS translates domain names (e.g. google.com) into IP addresses [1]. It is needed because computers communicate using IP addresses, not domain names [1], and DNS allows users to type easy-to-remember names rather than memorising numerical IP addresses [1].
Key Takeaways
What to Remember
Protocol: agreed rules for communication between devices
TCP/IP: internet foundation; HTTP: web; HTTPS: secure web; FTP: file transfer
DNS: domain → IP address; DHCP: auto-assigns IP addresses on a network
HTTPS encrypts data; HTTP does not — always prefer HTTPS for secure communication