DNSquerys

DNSquerys are requests to the Domain Name System used to obtain information about domain names. A DNSquery asks a DNS server for a specific record associated with a domain, such as an IP address, mail server, or other data.

There are different modes: recursive queries and iterative queries. In a recursive query, the client asks a single server to resolve the name completely and deliver the final answer. In an iterative query, the server provides referrals to other servers closer to the answer.

Resolution process: A typical client uses a recursive resolver. The resolver starts at a root server to locate the appropriate top-level domain server, then queries the TLD server, and finally queries the authoritative server for the domain. Caching at the resolver and clients reduces load and speeds future queries.

DNS messages and records: A query specifies the domain name and a record type, such as A, AAAA, MX, NS, CNAME, or TXT, in the IN class. The response contains an answer section with matching records, and may include authority and additional sections. Queries generally use UDP on port 53, with TCP used for large responses or zone transfers; EDNS0 allows larger UDP payloads.

Security and privacy: Traditional DNS provides no built-in authentication or encryption. DNSSEC can add cryptographic signatures to verify record integrity, though it does not encrypt queries. Encrypted options such as DNS over HTTPS and DNS over TLS aim to protect query privacy from eavesdropping and manipulation.

Practical considerations: DNS caching and TTL values influence performance and freshness. Misconfigurations or abuse can lead to cache poisoning or resolution failures. Common diagnostic tools include dig and nslookup.