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A step-by-step animation that tells the story of the DNS from the why in six acts and 27 steps. An IP address says where a host is and depends on its provider, so moving breaks everything that had it written down; a name adds a level of indirection managed by its owner. The name table starts as a central file (HOSTS.TXT) that does not scale and becomes a distributed, hierarchical database delegated in zones, whose tree does not match the address tree. The end host only asks the local resolver one question and waits; behind it, the local resolver walks the root, the .es TLD and the authoritative server to resolve www.rediris.es, with referrals, glue, the RD, RA and AA bits and the cache, on a map and a sequence diagram built side by side. It then shows that recursive and iterative describe each query-response pair, what would happen if everything were recursive or everything iterative, and ends with the eight messages, their destination and their sections (Question, Answer, Authority, Additional).
Concepts: IP address, level of indirection, domain name, A record, TTL, HOSTS.TXT, name tree, zone, delegation, stub resolver, local resolver, root server, TLD server, authoritative server, referral, glue record, cache, recursive query, iterative query, RD bit, RA bit, AA bit, sequence diagram.
Network Architecture I, Session 2.2 · Enrique de la Hoz, University of Alcalá · License CC BY-SA 4.0 · Source and catalogue on GitHub · DOI 10.5281/zenodo.23285664