WAN Configurations, Devices & Protocols

LANs connect a building; WANs connect the world. This subtopic covers the hardware, transmission methods and — critically — the protocols that make the Internet work.

WAN devices and transmission:

Gateway — a device/node that connects two different types of networks, translating between different protocols if needed.
Wi-Fi router — in a WAN context, connects a local network to a wider network via an ISP.
Transmission methods — satellite (very long distance, higher latency), radio waves and microwave transmission (used for point-to-point links, e.g. between cell towers).

Connection technologies:

Technology	Notes
Cellular technologies	Mobile data standards (e.g. 4G, 5G) — newer generations offer higher speed and lower latency
Fibre	Uses light through glass/plastic cable; very high speed and bandwidth, low latency
ADSL	Uses existing telephone lines; slower and more distance-limited than fibre, but more widely available in some areas

Fibre vs ADSL generally differ in usage and bandwidth: fibre supports much higher bandwidth (better for streaming, gaming, large uploads) while ADSL is often more limited, especially for upload speed.

Protocols — the agreed 'rules of communication' different Internet services use:

Category	Protocols	Purpose
Email	POP3, IMAP, SMTP	POP3 downloads and typically removes mail from the server; IMAP keeps mail synced on the server across devices; SMTP is used to send outgoing mail
Internet (transport)	TCP/IP — TCP vs UDP	TCP is reliable and ordered (confirms delivery, resends lost data) — used where accuracy matters, e.g. file downloads. UDP is faster but unreliable (no delivery confirmation) — used where speed matters more than perfection, e.g. live video/voice calls
Web	HTTP, HTTPS	HTTP transfers web page data; HTTPS is the encrypted, secure version of HTTP
Download/file transfer	FTP, WebDAV	FTP transfers files between a client and server; WebDAV extends HTTP to allow collaborative editing and management of files on a remote server

Example

Streaming a live sports match uses UDP-based delivery (via a video protocol) because a slightly dropped frame is far less disruptive than the delay that would come from TCP re-requesting every single lost packet.

💡 Exam Tip

A very common exam question: 'Explain why TCP is used for X but UDP is used for Y.' Always link your answer to whether reliability (TCP) or speed/low-latency (UDP) matters more for that specific use case.