DNS — Hierarchy, Records & TTL

Name → IP via a hierarchical distributed database. Client asks recursively; the resolver iterates: root → TLD → authoritative, then caches the answer per TTL. UDP/53 for queries, TCP/53 for zone transfers, DNSSEC and truncated answers. Record Purpose A / AAAA IPv4 / IPv6 CNAME alias MX mail exchangers NS authoritative servers PTR reverse (IP→name) […]