The host asks its local DNS server for the address of gaia.cs.umass.edu, with every cache empty. The rule in practice: the first query is recursive; all the others are iterative.
Message-by-message animation of how a host resolves gaia.cs.umass.edu with every cache empty, in a scenario made of a host, a local DNS server, a root server, a .edu TLD server and an authoritative server. It has three modes: iterative, recursive and a side-by-side comparison. Each of the 8 messages states its type (query, referral or answer), its fields (RD, AA, TTL) and what gets cached, and marks which servers hold someone else's query pending. It shows that in practice only the first query is recursive, and that root and TLD servers reply with referrals so that they do not accumulate pending queries.
Concepts: iterative query, recursive query, local DNS server, referral, authoritative server, cache, TTL, root server.
Network Architecture I, Session 2.1 · Enrique de la Hoz, University of Alcalá · License CC BY-SA 4.0 · Source and catalogue on GitHub · DOI 10.5281/zenodo.23285664