Wired and Wireless Networks, Protocols and Layers

Devices can connect to a network using wired or wireless technology. OCR J277 names three connection methods:

Method	Type	Technology
Ethernet	Wired	Uses copper or fibre-optic cables; data sent as electrical or light pulses
Wi-Fi	Wireless	Uses radio waves; devices connect to a wireless access point
Bluetooth	Wireless	Uses short-range radio waves; designed for direct device-to-device connections at close range

OCR J277 requires understanding of benefits and drawbacks of wired vs. wireless, and knowing which connection method suits a given scenario. How Ethernet, Wi-Fi, and Bluetooth work internally is NOT required.

Comparing wired and wireless:

Factor	Wired (Ethernet)	Wireless (Wi-Fi/Bluetooth)
Speed	Fast and consistent	Variable; affected by interference
Reliability	High — not subject to interference	Lower — signal weakens with distance/obstacles
Security	More secure — physical access required	Less secure — signals can be intercepted
Convenience	Requires physical cable to each device	No cables; devices can move freely
Cost	Higher infrastructure cost (cabling)	Lower per-device cost; no cabling

Scenario guidance:

• Fixed desktop computers in a school → wired (reliable, secure, consistent speed)
• Laptops used in different rooms → Wi-Fi (mobility essential)
• Wireless headphones or keyboard → Bluetooth (short-range, no infrastructure needed)

Encryption is the process of converting data into an unreadable form (ciphertext) using a mathematical algorithm and a key. Only someone with the correct decryption key can restore the original data.

On networks, encryption protects data while it is being transmitted — even if intercepted, it cannot be read without the key.

• HTTPS uses encryption (TLS/SSL) to protect data sent between browsers and websites
• Wi-Fi encryption (e.g. WPA2/WPA3) protects wireless transmissions from being intercepted by nearby devices

Every device on a network needs an address so data can be routed correctly.

IP address:

• Assigned to a device for communication across networks
• Used by routers to route data packets from source to destination
• Two versions: IPv4 (e.g. 192.168.1.10 — 32-bit, ~4.3 billion addresses) and IPv6 (e.g. 2001:0db8:85a3::8a2e:0370:7334 — 128-bit, vastly more addresses)
• IPv6 was introduced because IPv4 addresses were running out as the internet grew

NOT required: understanding the difference between static/dynamic or public/private IP addresses.

MAC address:

• A unique identifier permanently assigned to a network device's hardware (NIC) at manufacture
• Format: 6 pairs of hexadecimal digits, e.g. A1:B2:C3:D4:E5:F6
• Used within a local network (LAN) to identify specific devices; switches use MAC addresses to direct data to the correct device
• Cannot normally be changed (it is "burned in" to the hardware)

Key distinction: IP addresses identify a device's location on a network (and can change). MAC addresses identify the device itself (fixed at manufacture).

A standard is a published set of rules or specifications that define how hardware or software should behave. Standards allow products from different manufacturers to work together.

Why standards matter: Without them, a network card from one manufacturer could not communicate with a router from another. Standards ensure interoperability.

Examples: Ethernet is defined by a standard (IEEE 802.3); Wi-Fi by IEEE 802.11. These standards mean any compliant device can connect to any compliant network.

NOT required: knowledge of specific standard names or numbers (e.g. "IEEE 802.3").

A protocol is a set of rules that defines how data is formatted, transmitted, and received across a network. Protocols ensure devices made by different manufacturers can communicate.

Protocol	Full name	Purpose
TCP/IP	Transmission Control Protocol / Internet Protocol	Foundation of internet communication; breaks data into packets, routes them across networks, and reassembles them at the destination; ensures reliable delivery
HTTP	HyperText Transfer Protocol	Used by web browsers to request and receive web pages
HTTPS	HyperText Transfer Protocol Secure	Encrypted version of HTTP; protects data between browser and web server
FTP	File Transfer Protocol	Used to transfer files between computers over a network
POP	Post Office Protocol	Downloads emails from a mail server to the user's device; messages are removed from the server
IMAP	Internet Message Access Protocol	Accesses emails on the mail server without downloading them; messages remain on the server and can be read from multiple devices
SMTP	Simple Mail Transfer Protocol	Used to send email from a client to a server, and between servers

Email protocol summary:

• SMTP = sending email outward
• POP = receiving email by downloading (removes from server)
• IMAP = receiving email by accessing server copy (keeps on server, synchronised across devices)

When data is sent across a network, multiple things must happen: the message must be formatted, addressed, broken into packets, transmitted physically, and reassembled. Managing all of this in one monolithic system would be extremely complex to design and maintain.

Protocol layers solve this by dividing the communication process into distinct layers, each responsible for a specific job. Each layer only needs to know about the layers immediately above and below it.

Benefits of using layers:

• Separation of concerns — each layer has a single, clear responsibility
• Interoperability — as long as layers communicate via agreed interfaces, hardware/software from different manufacturers can work together
• Ease of development — a layer can be updated or replaced without affecting other layers

The TCP/IP model (used as the teaching example in OCR J277) has 4 layers:

Layer	Responsibility
Application	The application-level protocols (HTTP, FTP, SMTP, etc.) — how software communicates
Transport	Breaks data into packets, ensures reliable delivery (TCP), manages error checking
Internet/Network	IP addressing and routing — getting packets from source to destination across networks
Link/Network access	Physical transmission of data over the actual medium (cable, Wi-Fi)

NOT required: memorising the names and functions of each individual TCP/IP layer.

1. Confusing SMTP and IMAP/POP

SMTP is for sending email. POP and IMAP are for receiving email. A common mistake is attributing SMTP to receiving, or confusing the direction of each protocol.

2. Saying IP and MAC addresses do the same thing

IP address identifies where a device is on a network (logical, can change). MAC address identifies the device itself (physical, fixed). Routers use IP addresses; switches use MAC addresses.

3. Saying HTTP and HTTPS are different protocols

HTTPS is HTTP with encryption added (via TLS). The underlying protocol is the same; HTTPS adds a security layer. The "S" stands for Secure.

4. Saying layers mean "slower communication"

Layers add abstraction for manageability, not significant overhead. The benefit is modularity and interoperability — any layer can change internally without breaking others.

Mistake	Correction
"IMAP downloads emails to my device"	IMAP accesses emails on the server without downloading; POP downloads and removes them from the server
"A protocol and a standard are the same thing"	A standard is a published specification; a protocol is a set of rules for data transfer. They are related but not identical
"Bluetooth has the same range as Wi-Fi"	Bluetooth is designed for short-range (typically ~10m) device pairing; Wi-Fi covers much larger areas