{"id":20340,"date":"2020-01-29T15:01:08","date_gmt":"2020-01-29T15:01:08","guid":{"rendered":"https:\/\/www.arimetrics.com\/glosario-digital\/dns"},"modified":"2026-10-02T11:31:08","modified_gmt":"2026-10-02T11:31:08","slug":"dns","status":"publish","type":"encyclopedia","link":"https:\/\/www.arimetrics.com\/en\/digital-glossary\/dns","title":{"rendered":"DNS"},"content":{"rendered":"<p><img decoding=\"async\" class=\"boxpad alignright wp-image-14206 size-full\" style=\"margin-top:0;\" src=\"https:\/\/www.arimetrics.com\/wp-content\/uploads\/2020\/01\/DNS.png\" alt=\"DNS\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.arimetrics.com\/wp-content\/uploads\/2020\/01\/DNS.png 300w, https:\/\/www.arimetrics.com\/wp-content\/uploads\/2020\/01\/DNS-150x150.png 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><strong>Definition:<\/strong><\/p>\n<p><strong>DNS<\/strong> stands for <em>Domain Name System<\/em>. It is a hierarchical, distributed system used to retrieve information associated with a <a href=\"https:\/\/www.arimetrics.com\/en\/digital-glossary\/domain\">domain name<\/a>. Its best-known function is finding the <a href=\"https:\/\/www.arimetrics.com\/en\/digital-glossary\/ip\">IP address<\/a> of a server, but DNS also publishes data about mail, authoritative name servers, verification and other services.<\/p>\n<p>DNS prevents people and applications from having to know the numerical address of every resource. It is not a single server or a central copy of the Internet: responsibility is distributed across zones and servers, and caches are used to provide faster responses.<\/p>\n\n<h2>How a DNS query works<\/h2>\n<p>When an application needs to resolve a name, it normally sends the query to a recursive resolver configured on the device or network. If the answer is not cached, the process can be summarized as follows:<\/p>\n<ol>\n<li><strong>Application request:<\/strong> the user enters a <a href=\"https:\/\/www.arimetrics.com\/en\/digital-glossary\/url\">URL<\/a> or an application requests a name.<\/li>\n<li><strong>Resolver query:<\/strong> the operating system asks its configured recursive DNS server, which may be operated by an Internet provider, an organization or a public service.<\/li>\n<li><strong>Hierarchical lookup:<\/strong> if it has no valid cached answer, the resolver queries root, top-level domain and authoritative servers through successive referrals.<\/li>\n<li><strong>Authoritative response:<\/strong> the server responsible for the zone returns the requested record or reports that it does not exist.<\/li>\n<li><strong>Use and storage:<\/strong> the resolver returns the answer to the application and may store it for the period allowed by its TTL. The <a href=\"https:\/\/www.arimetrics.com\/en\/digital-glossary\/browser\">browser<\/a> can then initiate the relevant connection.<\/li>\n<\/ol>\n<p>The response does not always contain an IP address directly. A CNAME alias, for example, may require additional queries before the necessary data is found.<\/p>\n<h2>Components of the DNS hierarchy<\/h2>\n<p>A typical resolution combines components with different functions:<\/p>\n<ul>\n<li><strong>Recursive resolver:<\/strong> receives the request from the device, looks for the answer and maintains a cache. It is not necessarily authoritative for the queried domain.<\/li>\n<li><strong>Root servers:<\/strong> direct the resolver to the relevant top-level domain servers, such as those for <code>.com<\/code> or <code>.uk<\/code>.<\/li>\n<li><strong>TLD servers:<\/strong> indicate which name servers are responsible for the registered domain within that top-level domain.<\/li>\n<li><strong>Authoritative servers:<\/strong> publish the records for a DNS zone and provide the reference answer for the names they manage.<\/li>\n<\/ul>\n<p>A server may perform more than one role in some environments, but resolving queries for clients and publishing authoritative zone data remain distinct functions.<\/p>\n<h2>Types of DNS records<\/h2>\n<p>Resource records associate different types of information with a name:<\/p>\n<ul>\n<li><strong>A:<\/strong> maps a name to an IPv4 address.<\/li>\n<li><strong>AAAA:<\/strong> maps a name to an IPv6 address.<\/li>\n<li><strong>CNAME:<\/strong> declares that one name is an alias of another canonical name.<\/li>\n<li><strong>MX:<\/strong> identifies the servers that receive mail for a domain and their priority.<\/li>\n<li><strong>NS:<\/strong> specifies the authoritative servers for a zone or delegation.<\/li>\n<li><strong>TXT:<\/strong> contains text used for purposes including verification and email-related policies.<\/li>\n<li><strong>SOA:<\/strong> provides administrative information about the zone, including its primary server and update parameters.<\/li>\n<li><strong>PTR:<\/strong> is primarily used in reverse resolution to associate an address with a name.<\/li>\n<\/ul>\n<p>Changing a DNS record does not move a website, mailbox or its files by itself. It changes the published information used to locate or verify those services.<\/p>\n<h2>DNS caching, TTL and propagation<\/h2>\n<p>DNS responses include a <em>time to live<\/em>, or TTL, which specifies how long they may be cached. While a cached copy remains valid, the resolver can answer without repeating the full hierarchical lookup.<\/p>\n<p>The expression &#8220;DNS propagation&#8221; describes the period during which different resolvers allow old data to expire and retrieve the new data. No copy is updated simultaneously on every server. The time observed depends on the previous TTL, intermediate caches and the zone configuration.<\/p>\n<p>This distributed, cache-based model is part of the design described in <a href=\"https:\/\/www.rfc-editor.org\/rfc\/rfc1034.html\" target=\"_blank\" rel=\"noopener\">RFC 1034<\/a> and helps the system operate at <a href=\"https:\/\/www.arimetrics.com\/en\/digital-glossary\/internet\">Internet<\/a> scale.<\/p>\n<h2>DNS security and privacy<\/h2>\n<p>The original DNS was not designed to cryptographically verify every response or encrypt queries. Several technologies address different requirements:<\/p>\n<ul>\n<li><strong>DNSSEC:<\/strong> allows the origin and integrity of signed data to be validated through a chain of trust; it does not encrypt the query.<\/li>\n<li><strong>DNS over HTTPS (DoH):<\/strong> transports queries and responses between a client and resolver over HTTPS.<\/li>\n<li><strong>DNS over TLS (DoT):<\/strong> encrypts that segment using a TLS connection specifically for DNS.<\/li>\n<li><strong>Operational protections:<\/strong> validation, query randomization, redundancy and correct configuration reduce risks such as cache poisoning, but do not eliminate every threat.<\/li>\n<\/ul>\n<p>Transport encryption and data authentication are different properties. Using DoH or DoT does not mean that a response has been validated with DNSSEC, and DNSSEC does not by itself conceal which name is being queried.<\/p>\n<h2>DNS vs. domain, URL and hosting<\/h2>\n<p>These concepts all contribute to accessing a website, but they are not interchangeable:<\/p>\n<ul>\n<li><strong>DNS:<\/strong> is the distributed query system that publishes information associated with names.<\/li>\n<li><strong>Domain:<\/strong> is a name registered within the hierarchy, such as <code>example.com<\/code>.<\/li>\n<li><strong>URL:<\/strong> identifies the location of or access method for a resource and includes elements beyond the domain, such as the scheme and path.<\/li>\n<li><strong>Hosting:<\/strong> is the infrastructure that stores a website, mail or other services. Changing <a href=\"https:\/\/www.arimetrics.com\/en\/digital-glossary\/hosting\">web hosting<\/a> often requires DNS record updates, but they are separate services.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Definition: DNS stands for Domain Name System. It is a hierarchical, distributed system used to retrieve information associated with a domain name. Its best-known function is finding the IP address of a server, but DNS also publishes data about mail, authoritative name servers, verification and other services. DNS prevents people and applications from having to [&hellip;]<\/p>\n","protected":false},"author":6,"featured_media":0,"template":"","encyclopedia-tag":[1256,1267,1458],"class_list":["post-20340","encyclopedia","type-encyclopedia","status-publish","hentry","encyclopedia-tag-domains","encyclopedia-tag-web-infrastructure","encyclopedia-tag-web-server-infrastructure"],"_links":{"self":[{"href":"https:\/\/www.arimetrics.com\/en\/wp-json\/wp\/v2\/encyclopedia\/20340","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.arimetrics.com\/en\/wp-json\/wp\/v2\/encyclopedia"}],"about":[{"href":"https:\/\/www.arimetrics.com\/en\/wp-json\/wp\/v2\/types\/encyclopedia"}],"author":[{"embeddable":true,"href":"https:\/\/www.arimetrics.com\/en\/wp-json\/wp\/v2\/users\/6"}],"wp:attachment":[{"href":"https:\/\/www.arimetrics.com\/en\/wp-json\/wp\/v2\/media?parent=20340"}],"wp:term":[{"taxonomy":"encyclopedia-tag","embeddable":true,"href":"https:\/\/www.arimetrics.com\/en\/wp-json\/wp\/v2\/encyclopedia-tag?post=20340"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}