Glossary of DNS Terms

Here's a comprehensive glossary of common terms you'll encounter when working with the Domain Name System (DNS), designed to help you understand the foundational concepts.

• A Record (Address Record): A fundamental DNS record type that maps a domain name to an IPv4 address. This is how browsers find the numerical address of a website.

• AAAA Record (IPv6 Address Record): Similar to an A record, but maps a domain name to an IPv6 address. Essential for the modern internet's addressing scheme.

• Authoritative Nameserver: A nameserver that holds the definitive DNS records for a specific domain. It provides direct answers to DNS queries for that domain.

• CAA Record (Certificate Authority Authorization): A DNS record that specifies which Certificate Authorities (CAs) are authorized to issue certificates for a domain. Helps prevent unauthorized certificate issuance.

• CNAME Record (Canonical Name Record): Creates an alias that points one domain name to another canonical (true) domain name. For example, www.example.com might be a CNAME for example.com.

• DNS (Domain Name System): A hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It translates human-readable domain names into machine-readable IP addresses.

• DNS Propagation: The time it takes for DNS changes to update and synchronize across all DNS servers worldwide. This process is not instantaneous.

• DNS Resolver (Recursive Nameserver): A server that queries authoritative nameservers on behalf of users to find the IP address for a domain. It caches responses to speed up future requests.

• DNSSEC (Domain Name System Security Extensions): A suite of IETF specifications for securing certain kinds of information provided by the Domain Name System (DNS) as used on Internet Protocol (IP) networks. It adds cryptographic authentication to DNS.

• DKIM (DomainKeys Identified Mail): An email authentication method designed to detect email spoofing by allowing the receiver to check that an email claimed to come from a specific domain was indeed authorized by the owner of that domain.

• DMARC (Domain-based Message Authentication, Reporting, and Conformance): An email authentication protocol that uses SPF and DKIM to determine the authenticity of an email message. It tells receiving mail servers how to handle emails that fail SPF or DKIM checks.

• Domain Name: A human-readable name for a website or online service (e.g., deep-dns.com). It's what users type into their browsers.

• FQDN (Fully Qualified Domain Name): A complete domain name that specifies its exact location in the DNS hierarchy, including the hostname and all domain labels up to the TLD (e.g., www.example.com.).

• Glue Record: An A record that provides the IP address of a nameserver that is authoritative for the domain it serves. Used to prevent circular dependencies when a nameserver uses the domain it is authoritative for (e.g., ns1.example.com for example.com).

• IP Address: A numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It uniquely identifies a device on a network.

• MX Record (Mail Exchange Record): Specifies the mail server(s) responsible for accepting email messages on behalf of a domain name. Includes a priority value for multiple servers.

• Nameserver: A specialized server that stores the DNS records for a domain and responds to DNS queries, translating domain names into IP addresses.

• PTR Record (Pointer Record): Used for reverse DNS lookups, mapping an IP address back to a domain name. Often used for email server validation.

• Registrar: A company or organization accredited to manage the reservation of Internet domain names. You purchase your domain name through a registrar.

• Root Domain: The primary domain name you register (e.g., example.com), without any subdomains.

• Root Nameserver: The highest level in the DNS hierarchy, responsible for directing queries to the correct Top-Level Domain (TLD) nameservers.

• SPF (Sender Policy Framework): An email authentication method designed to detect forging sender addresses by allowing domain owners to publish a list of authorized sending mail servers in a TXT record.

• SRV Record (Service Record): Defines the location (hostname and port number) of specific services within a domain, such as VoIP or instant messaging.

• SSL/TLS (Secure Sockets Layer/Transport Layer Security): Cryptographic protocols designed to provide communications security over a computer network, primarily used for encrypting web traffic (HTTPS).

• Subdomain: A domain that is part of a larger domain (e.g., blog.example.com is a subdomain of example.com). Used to organize content or services.

• TLD (Top-Level Domain): The last segment of a domain name (e.g., .com, .org, .net, .io, country codes like .uk).

• TTL (Time to Live): A value in a DNS record that specifies how long a DNS resolver is supposed to cache the record before querying for fresh information. Impacts DNS propagation speed.

• TXT Record (Text Record): A versatile DNS record type that holds arbitrary human-readable text. Used for various purposes, including email authentication (SPF, DKIM, DMARC) and domain verification.

• WHOIS: A query and response protocol used for querying databases that store the registered users or assignees of an Internet resource, such as a domain name, an IP address block, or an autonomous system.