AQA/OCR GCSE CS: Protocols & Layers

1. Wired & Wireless Connections

Computers connect via physical media (wired) or radio waves (wireless).

Wired: Ethernet

Speed: Very high and stable.
Security: Harder to intercept as you need physical access.
Reliability: No interference from walls or other devices.

Wireless: Wi-Fi & Bluetooth

Wi-Fi: High range (~50m), connects many devices.
Bluetooth: Short range (~10m), low power, direct device-to-device.
Security: Easier to intercept; requires Encryption.

2. IP vs MAC Addressing

Every device needs an address to receive data, but there are two different types.

MAC Address: Hard-coded into the NIC at the factory. It is permanent and 48-bits (Hexadecimal). It identifies the physical device.
IP Address: Assigned by the network. It can change. IPv4 (32-bit decimal) is running out, so we are moving to IPv6 (128-bit hexadecimal).

Standards

Standards are rules that allow hardware and software from different manufacturers (e.g., Apple and Samsung) to work together. Without standards like Wi-Fi (802.11) or USB, devices couldn't talk to each other.

3. Network Protocols

A protocol is a set of rules for transferring data. Here are the ones you must know:

Web & Files:
• HTTP: Web page requests.
• HTTPS: Secure, encrypted web traffic.
• FTP: Sending/receiving large files.

Email:
• SMTP: Sending mail to a server.
• POP: Downloads and deletes mail.
• IMAP: Syncs mail across devices.

TCP/IP: The master protocol. TCP handles the packets; IP handles the routing.

4. The 4-Layer TCP/IP Model

Layering breaks networking into manageable parts. Benefits include: developers only need to focus on one layer, and standards are easier to enforce.

Application Layer: Where apps (browsers/email) produce data. (HTTP, FTP, SMTP)
Transport Layer: Splits data into packets and checks for errors. (TCP)
Internet Layer: Adds IP addresses and routes the packets. (IP)
Link Layer: Physical connection via cables/radio. (Ethernet/Wi-Fi)

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