Cache hit
A query answered from cached data without contacting an upstream authoritative server. A high cache-hit rate can reduce latency and upstream load, though the right rate depends on workload and TTLs.
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Browse the glossaryOperations glossary
26 definitions associated with Operations.
Browse Operations definitions
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Page 1 of 2Cache miss
A query for which the resolver does not have usable cached data and must perform resolution or forwarding. Misses increase upstream traffic and usually add latency.
Read definitionCapacity planning
Forecasting when address pools, prefixes, DHCP capacity, or DNS infrastructure will need expansion. Useful inputs include utilization, growth rate, lease churn, query rate, and failure-domain requirements.
Read definitionConfiguration drift
A difference between intended configuration and the state actually deployed across servers, appliances, cloud services, or data stores. Drift can create inconsistent answers, overlapping allocations, and failover risk.
Read definitionCUDN
A centrally operated user-facing recursive DNS service, often used as an organizational resolver platform. The acronym is less universal than common terms such as recursive resolver.
Read definitionDNS anomaly
A query or response pattern that differs from expected behavior, such as sudden NXDOMAIN growth, unusual labels, rare record types, high entropy, or traffic from an unexpected client. An anomaly is a signal, not proof of malicious activity.
Read definitionDNS flag day
A coordinated industry event after which participating DNS software stops accommodating a legacy or non-compliant behavior. The goal is to accelerate protocol hygiene by changing defaults at the same time.
Read definitiondnstap
A structured binary event stream for recording DNS message and resolver processing data. It provides richer and often more efficient telemetry than plain-text query logs.
Read definitionEDNS buffer size
The UDP payload size a requester advertises in the OPT record. Oversized values can cause fragmentation or path failures, while undersized values cause more truncation and TCP or QUIC fallback.
Read definitionFreeze
A product operation that temporarily stops dynamic modifications to a zone so its backing file or data can be edited safely. In BIND, thaw resumes normal dynamic update processing.
Read definitionGarbage collection
Automatic cleanup of expired leases, stale records, orphaned objects, old logs, or unreferenced data. Cleanup policy should preserve audit history while preventing stale state from becoming operational truth.
Read definitionICMP echo
The request and reply messages commonly used by ping. Some DHCP servers use ICMP echo as one signal in IPv4 conflict detection, though lack of reply does not prove an address is unused.
Read definitionJournal
A change log used by a DNS server to support dynamic update recovery and incremental zone transfers. Journal file formats and retention are implementation-specific.
Read definitionLast known good
A previously validated configuration or data state retained for rollback or recovery. DDI changes should define how to restore a last-known-good zone, database, or service configuration.
Read definitionNXDOMAIN spike
A sudden rise in nonexistent-name responses. Causes can include typos, missing suffixes, search-list behavior, stale applications, DGAs, random-subdomain attacks, or failed service discovery.
Read definitionPing
A diagnostic operation that sends ICMP echo requests and measures replies. Ping tests IP reachability, not DNS correctness or application availability, and devices may intentionally ignore it.
Read definitionProbe
An active test used to measure reachability, latency, correctness, or service health. DNS probes may query specific names and validate answers, flags, timing, and server identity.
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 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 definitionRTT
Round-trip time, the elapsed time for a request to travel to a destination and a response to return. DNS RTT measurements should distinguish client-to-resolver and resolver-to-authoritative paths.
Read definitionService level agreement (SLA)
A formal commitment for measurable service outcomes such as availability, response time, support, or recovery. DDI SLAs should define measurement points and exclusions.
Read definitionService level objective (SLO)
A target for a service indicator, such as successful DNS responses, DHCP allocation time, or platform availability. SLOs are internal engineering objectives and may support an SLA.
Read definitionSource of truth
The system or governed data set designated as authoritative for a class of information. In DDI, one system may own intended allocation while discovery or DHCP owns observed runtime state, so ownership must be explicit.
Read definitionSynthetic monitoring
Automated tests that periodically perform DNS lookups, DHCP transactions, API calls, or application checks from controlled probes. It measures user-like outcomes even when no real user reports an issue.
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