Internet
Internet
This domain covers how the global network is addressed and used: IP and DNS, WWW, URL structure, email, search, and common protocols. Questions often ask you to identify components of a URL or choose the right protocol/service.
Core rules
- The Internet is a network of networks; the WWW is one service on it. ISP provides access.
- DNS translates domain names to IP addresses. An IP address identifies an interface; a domain name is human-readable.
- HTTP/HTTPS transfer web pages; HTTPS adds TLS encryption. SMTP sends mail; POP3/IMAP retrieve mail.
- A URL contains scheme, host, optional port, path, query and fragment.
- Search engines crawl and index pages; they do not store the whole live web in one database.
Worked example
Take https://www.example.com:443/notes/page.html?q=html#top. Scheme: https. Host: www.example.com. Port: 443. Path: /notes/page.html. Query: q=html. Fragment: top. The reasoning is positional: the fragment follows # and is handled by the browser; the query follows ? and is sent to the server.
Traps
Do not call the domain name an IP address. http:// is not encrypted; https:// uses TLS. The @ in an email address separates local part and domain; it is not part of a URL. A web browser is a client, not a search engine. In email, SMTP is for sending, not for downloading inbox messages.