SPF
Sender Policy Framework, an email-authentication mechanism that publishes which systems are authorized to send mail for a domain, normally in a DNS TXT record. The dedicated SPF RR type is obsolete for deployment.
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Browse the glossaryDNS glossary — page 12
311 definitions associated with DNS.
Browse DNS definitions
311 matching terms
Page 12 of 13Split DNS
A design in which the same name or namespace produces different data depending on the requesting client or network context. It can be implemented with views, separate authoritative systems, private zones, or resolver policy.
Read definitionSplit horizon
A common synonym for split DNS. The same namespace is presented differently to different audiences.
Read definitionSRV record
A Service record identifies the target host and port for a named service, with priority and weight values for selection. The owner name normally begins with _service._protocol.
Read definitionStale answer
An expired cached response served by a resolver when authoritative refresh is temporarily impossible and policy permits serving stale data. It can improve resilience during outages while carrying an EDE explanation.
Read definitionStale record
A record that no longer reflects the current device, address, owner, or service. Stale data can cause misrouting, security exposure, and incorrect capacity reports.
Read definitionStatic record
A DNS record created without an aging timestamp or otherwise protected from automatic scavenging. "Static" describes management behavior, not a distinct DNS record type.
Read definitionStealth server
An authoritative server not listed in the public NS RRset, often used as a hidden primary or internal transfer source. The term is informal.
Read definitionStub resolver
A simple resolver on an endpoint that sends queries to a recursive resolver and does little or no iterative resolution itself. Operating-system libraries commonly provide stub functionality.
Read definitionStub zone
A zone configuration containing only enough authoritative data, usually SOA, NS, and glue, to locate the zone's current authoritative servers. It tracks delegation data without storing the full zone.
Read definitionSubdelegation
A delegation from one zone to a child zone below it. Each subdelegation creates a new zone cut and administrative boundary.
Read definitionSubdomain
A domain contained beneath another domain in the DNS hierarchy. A subdomain is not necessarily a separate zone unless a delegation creates a zone cut.
Read definitionSubdomain takeover
An attack in which a DNS record points to a deprovisioned third-party resource that an attacker can claim. Removing dangling records and validating external targets reduces risk.
Read definitionSuffix
A sequence of ending labels in a domain name. DNS hierarchy, search lists, public-suffix policy, and QNAME minimization all use suffix concepts in different ways.
Read definitionSVCB record
A Service Binding record that describes alternative service endpoints and connection parameters. It supports alias mode and service mode and is the base format specialized by the HTTPS record.
Read definitionSvcParam
A key-value parameter carried in SVCB or HTTPS RDATA, such as alpn, port, ipv4hint, ipv6hint, ech, or mandatory. IANA maintains the parameter-key registry.
Read definitionTC bit
The Truncated bit in a DNS response indicates that the message was shortened because it exceeded the available transport size. A client normally retries using TCP or another suitable transport.
Read definitionTCP fallback
Retrying a DNS query over TCP after a truncated UDP response or other transport need. Modern DNS implementations must support TCP and should reuse connections efficiently.
Read definitionThaw
A BIND operation that resumes dynamic update after a zone has been frozen and reloads changes made to its master file.
Read definitionTime to live (TTL)
The number of seconds a DNS record may be cached before it must be treated as expired. TTL choices affect change speed, query load, resilience, and negative or stale-answer behavior.
Read definitionTLD
Top-Level Domain, a direct child of the DNS root, such as com, org, net, or a country-code TLD. TLD zones are delegated from the root.
Read definitionTransaction ID
A 16-bit identifier used to match a DNS response to its query. UDP security also relies on source port, addresses, question content, cookies, and other transaction checks.
Read definitionTransaction signature (TSIG)
A shared-secret mechanism that authenticates DNS messages and protects integrity and replay context. It is commonly used for zone transfers, NOTIFY, and dynamic updates between trusted systems.
Read definitionTransfer source
The authoritative server from which a secondary requests AXFR or IXFR. The transfer source may be a hidden primary, another secondary, or a distribution layer.
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