Persistent connection
A TCP, TLS, QUIC, or other session reused for multiple DNS transactions rather than opened for each query. Persistence improves efficiency but requires connection limits and idle-time management.
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311 definitions associated with DNS.
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Page 9 of 13Persistent record
A record protected from automatic aging, scavenging, cleanup, or synchronization deletion. The term is product-specific and does not define a distinct DNS resource-record type.
Read definitionPreference
A relative selection value whose interpretation depends on the protocol. MX and SRV use numeric preference or priority, while DHCPv6 servers can send an OPTION_PREFERENCE value to influence client selection.
Read definitionPrimary DNS server
The authoritative server or data source from which a zone is provisioned and updated before changes reach secondaries. "Primary" describes the provisioning relationship, not necessarily traffic preference or a single server.
Read definitionPrimary zone
A locally writable authoritative zone whose source data is maintained on that server or integrated data store. Other servers can obtain copies through transfer or replication.
Read definitionPrivate hosted zone
A cloud-managed authoritative zone visible only within associated virtual networks, accounts, or resolver endpoints. Connectivity and resolver rules determine who can query it.
Read definitionPrivate namespace
A DNS namespace intended for limited administrative or network scope rather than the public DNS. Collision risk exists if an internal suffix later becomes delegated publicly or is used by another connected organization.
Read definitionProtective DNS
A recursive DNS service that uses threat intelligence and policy to block or redirect access to malicious domains while producing security telemetry. It can be delivered on premises, in cloud, or as a hybrid service.
Read definitionPTR record
A Pointer record maps a reverse-domain name to another domain name, most commonly mapping an IPv4 or IPv6 address to a host name. Multiple PTRs are technically possible but can confuse applications.
Read definitionPublic suffix
A domain suffix under which independent parties can register names, such as com or co.uk, as identified by policy data such as the Public Suffix List. It is not always the same as a DNS zone boundary.
Read definitionPunycode
The encoding algorithm used by IDNA to represent Unicode labels using ASCII characters. Encoded A-labels begin with xn--.
Read definitionQCLASS
The class field in a DNS question. IN is the normal value for Internet DNS queries.
Read definitionQNAME
The domain name in the question section of a DNS query. During alias processing, the original QNAME can lead to one or more other names and RRsets.
Read definitionQNAME minimization
A recursive-resolver technique that sends only the minimum name needed at each delegation step instead of exposing the full original query name to every upstream server. It improves privacy and can reduce unnecessary data disclosure.
Read definitionQPS
Queries per second, a common measurement of DNS request rate. Capacity planning should consider peaks, response sizes, cache behavior, query types, and failure scenarios rather than QPS alone.
Read definitionQR bit
The Query/Response bit in the DNS header. A value of 0 indicates a query and 1 indicates a response.
Read definitionQTYPE
The numeric type requested in a DNS question, such as A, AAAA, MX, or a meta-type such as ANY. QTYPE values share the IANA RR TYPE registry.
Read definitionQuery
A DNS message sent to request information or perform an operation. Most queries contain one question, though the protocol format can represent more.
Read definitionQuery logging
Recording DNS query metadata such as time, client, name, type, response code, latency, and selected policy. Logging improves troubleshooting and security visibility but requires privacy, retention, and volume controls.
Read definitionQuery name
A plain-language synonym for QNAME, the domain name being asked about in a DNS question.
Read definitionQuestion section
The DNS message section containing QNAME, QTYPE, and QCLASS. Normal queries usually contain one question.
Read definitionRandom subdomain attack
A denial-of-service technique that generates many unique labels beneath a target domain, defeating positive caching and forcing repeated authoritative work. It is also called DNS water torture.
Read definitionRCODE
The DNS response code indicating the outcome of a query or operation, such as NOERROR, FORMERR, SERVFAIL, NXDOMAIN, NOTIMP, or REFUSED. EDNS extends the original four-bit field.
Read definitionRD bit
The Recursion Desired bit in a query asks the server to perform recursive resolution if it supports and permits it. The server's RA bit indicates whether recursion is available.
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