Learning objectives
Distinguish the internet from the world wide web, and describe the roles of a URL, a domain name, a DNS server and an internet service provider when a browser requests a page
(A Level) Explain what a protocol is and state the service provided by HTTP, HTTPS, FTP, SMTP, POP3 and IMAP
(A Level) Explain why protocols are arranged in layers, name the four layers of the TCP/IP stack and state the job carried out at each layer as a message is sent and then received
(A Level) Describe the structure of a data packet as a header, a payload and a trailer, and explain how packets that travel by different routes are reassembled in the correct order
(A Level) Compare circuit switching with packet switching on route setup, use of bandwidth, delay and resilience, and identify an application suited to each
(A Level) Explain how BitTorrent lets peers share a file among themselves instead of fetching it from one server, using the terms piece, swarm, seed, leech and tracker
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