The Internet’s phonebook is called the Domain Name System<\/a> (DNS). Domain names<\/a> allow humans to access online information, such as espn.com and nytimes.com. Internet Protocol (IP), addresses are used by web browsers to interact with the Internet Protocol. DNS converts domain names into IP addresses so that browsers can load Internet resources. Every device connected to the Internet is assigned a unique IP address that other machines can use to locate it. DNS servers eliminate the need for humans to memorize IP addresses such as 192.168.1.1 (in IPv4), or more complex newer alphanumeric IP addresses such as 2400:cb00:2048:1::c629:d7a2 (in IPv6).<\/p>\n DNS resolution<\/a> is the conversion of a hostname, such as www.example.com, into a computer-friendly IP address (such 192.168.1.1). Each device connected to the Internet is assigned an IP address. This address allows them to locate the correct device. It is similar to a street address that is used to locate a house. A translation must be made between the user’s input (example.com), and the machine-friendly address needed to locate example.com webpage. Understanding the DNS resolution process<\/a> is important. It’s essential to know about the hardware components that a DNS query must pass through. The DNS lookup is done “behind the scenes” by the web browser and does not require any interaction beyond the initial request.<\/p>\n Both terms\u00a0refer to servers (groups\u00a0or\u00a0servers) that are\u00a0part of\u00a0the DNS infrastructure. However, each server\u00a0performs a different\u00a0function\u00a0and lives in different\u00a0places within the\u00a0DNS query pipeline.\u00a0The recursive resolver is\u00a0located\u00a0at the beginning of\u00a0a DNS query, while\u00a0the authoritative nameserver is\u00a0located\u00a0at the end.<\/p>\n Recursive resolvers are computers that respond to recursive requests from clients and take the time to find the DNS record. It makes a series of requests to reach the authoritative DNS nameserver for the requested records. If no record is found, it will return an error or times out. Recursive DNS resolvers don’t always have to make multiple requests to find the records required to reply to clients. Instead, caching is a data persistence process that helps to shorten the time between requests by serving the requested resource earlier in the DNS lookup.<\/p>\n An authoritative DNS server, in simple terms, is a server that holds and manages DNS resource records. This is the DNS server that responds to the query with the resource record. It allows the web browser to request the IP address to access the website or other web resources. Because it is the last source of truth for certain DNS records, an authoritative nameserver can answer queries using its own data. It is worth noting that in cases where the query is for a subdomain, such as foo.example.com and blog.cloudflare.com a second nameserver will be added after the authoritative nameserver. This is responsible for storing the subdomain’s CNAME records.<\/p>\n Cloudflare offers a unique DNS service that is different from many others. OpenDNS, Google DNS, and Comcast all have data center installations of DNS Recursive Resolvers. These resolvers enable quick and simple queries through optimized clusters and DNS-optimized computer system systems. However, they are fundamentally different from the nameservers hosted on Cloudflare. Cloudflare has infrastructure-level nameservers which are essential to the operation of the Internet. Cloudflare partially hosts the froot server network. This is a key example. F-root is a root-level DNS nameserver infrastructure component that handles billions of Internet requests each day. We are able to handle large volumes without interruption of service thanks to our Anycast network.<\/p>\n DNS refers to the translation of a domain name into an IP address. It is helpful to trace the DNS lookup’s journey from a web browser through the DNS lookup process<\/a> and back again. Let’s look at the steps. Not all\u00a0DNS lookup information\u00a0is stored locally on the querying machine\u00a0or remotely in the DNS infrastructure.\u00a0A DNS lookup\u00a0typically involves 8 steps.\u00a0The DNS lookup process\u00a0is faster\u00a0when DNS information\u00a0has been cached.\u00a0Here’s an example of the 8 steps that are skipped when no cached DNS information is available.<\/p>\n After\u00a0the DNS lookup\u00a0has completed 8 steps, the browser\u00a0can make a\u00a0request for the\u00a0requested web page.<\/p>\n The DNS resolver is the first\u00a0step\u00a0in the DNS lookup.\u00a0It is responsible for dealing\u00a0directly\u00a0with the client\u00a0who\u00a0made the initial request.\u00a0The DNS resolver initiates\u00a0the sequence of queries that\u00a0eventually leads to the\u00a0URL being translated into\u00a0an\u00a0IP address.<\/p>\n Notice: An\u00a0uncached DNS lookup\u00a0can include both iterative and recursive queries.<\/p>\n It is important to distinguish between a DNS query that is recursive and one that is recursive. A query is a request for a DNS resolution that requires the resolution of the query. DNS recursive resolvers are computers that receive a recursive question and process it by making the required requests.<\/p>\n Three types of queries\u00a0are possible in a DNS lookup.\u00a0A combination of these queries\u00a0can optimize DNS resolution and reduce the\u00a0distance traveled.\u00a0A perfect situation will have cached data, which allows a DNS\u00a0server to return a\u00a0nonrecursive query.<\/p>\n Caching temporarily stores\u00a0data in a location that\u00a0improves\u00a0performance and reliability\u00a0when data requests are made.\u00a0DNS caching<\/a> is the temporary storage of data near the client to resolve DNS queries earlier.\u00a0Additional queries further down the DNS lookup\u00a0chains\u00a0can be avoided. This can improve\u00a0load times and\u00a0reduce\u00a0bandwidth\/CPU usage.\u00a0DNS data can be\u00a0stored in many locations. Each location\u00a0will store DNS records for a\u00a0specific time period\u00a0determined by a time\u00a0to\u00a0live (TTL).<\/p>\n Modern web browsers automatically cache DNS records for a certain time. This is clear: the DNS cache must be located closer to the browser to allow for fewer steps to verify the cache and send the correct requests to the IP address. The browser cache is checked first for any DNS records when a request for one is made. In Chrome, you can see the status of your DNS cache by going to chrome:\/\/net-internals\/#dns.<\/p>\n The DNS resolver at the operating system level is the last stop before a DNS query leaves your computer. This query-handling process is known as a “stub solver” or DNS client. A stub resolver receives a request from an app. It first checks its cache to determine if it has that record. If it doesn’t, it sends a DNS query outside of the local network to an ISP DNS recursive solver. The ISP’s recursive resolver will receive a DNS query. Like all other steps, it will also check if the requested host-to-IP-address translation has been stored within its local persistence layer. Recursive resolvers also have additional functionality depending on the type of records they have in their cache.<\/p>\nHow does DNS work?<\/h2>\n
Four DNS servers are\u00a0involved in loading a website:<\/h2>\n
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What is the difference between an authoritative DNS server and a recursive DNS solver?<\/h2>\n
Recursive DNS resolver<\/h3>\n
Server for authoritative DNS<\/h3>\n
What are the steps involved in a DNS lookup?<\/h2>\n
These are\u00a0the 8 steps\u00a0to\u00a0a DNS lookup<\/h2>\n
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What is DNS resolution?<\/h2>\n
What are the\u00a0different\u00a0types of DNS queries?<\/h2>\n
There are three\u00a0types of DNS queries<\/h3>\n
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What is DNS caching?\u00a0What is DNS caching?<\/h2>\n
Caching DNS for browsers<\/h3>\n
DNS caching at the OS level<\/h3>\n
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