Difference between revisions of "DNS resolver"
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| − | On the [[Internet]], any [[DNS resolver]] (alternatively known as [[Internet Service Provider's DNS resolver]], [[ISP DNS resolver]], or, simply, [[resolver]]; hereinafter, the ''Resolver'') is any server that belongs to some Internet Service Provider | + | On the [[Internet]], any [[DNS resolver]] (alternatively known as [[Internet Service Provider's DNS resolver]], [[ISP's DNS resolver]], or, simply, [[resolver]]; hereinafter, the ''Resolver'') is any server that (a) belongs to some Internet Service Provider and (b) moderates any process of translating (resolving) human readable [[hostname]]s into [[IP address]]es that are used in communication between Internet hosts, or vice versa. The ''Resolvers'' are an essential part of [[DNS|Domain Name System]] ([[DNS]]). |
| − | The ''Resolvers'' receive requests in the form of a [[ | + | The ''Resolvers'' receive requests in the form of a [[hostname]] from a [[web browser]] and request the needed data from [[root nameserver]]s, which are the highest in the hierarchy, if the ''Resolvers'' haven't already cached that data. Indeed, the ''Resolvers'' not only redirect requests, but also cache the data needed to identify [[IP address]]es. |
==Name-to-IP-address process== | ==Name-to-IP-address process== | ||
The complete name-to-IP-address process can be described in the following way: | The complete name-to-IP-address process can be described in the following way: | ||
| − | #When the user enters a [[ | + | #When the user enters a [[hostname]] ([[hostname|domain name]]) into a [[web browser]], this browser queries their ''Resolver'' asking for the [[IP address]]. |
| − | #The ''Resolver'' asks the [[root | + | #The ''Resolver'' asks the [[root nameserver]] where it can find details for that [[hostname]], unless the resolver already has its [[IP address]] data cached. |
| − | #If it is asked, the [[root | + | #If it is asked, the [[root nameserver]] responds what [[TLD nameserver]] handles this data. |
| − | #The ''Resolver'' asks the [[TDL nameserver]] where it can find details for the entered [[ | + | #The ''Resolver'' asks the [[TDL nameserver]] where it can find details for the entered [[hostname]], unless it already has the data cached. |
| − | #If it is asked, the [[TLD nameserver]] responds that this data can be found at the [[ | + | #If it is asked, the [[TLD nameserver]] responds that this data can be found at the [[host nameserver]]s. |
| − | #The ''Resolver'' asks the [[ | + | #The ''Resolver'' asks the [[host nameserver]]s where it can find details for the needed [[IP address]], unless it already has the data cached. |
| − | #If it is asked, the [[ | + | #If it is asked, the [[host nameserver]]s have this data and respond with a [[DNS record]] containing the [[IP address]] for the entered [[hostname]]. |
#The ''Resolver'' sends the identified data back to the [[web browser]]. | #The ''Resolver'' sends the identified data back to the [[web browser]]. | ||
The name-to-IP-address process has been accomplished. Based on its results, the [[web browser]] points its request to the exact [[IP address]] in order to establish communication between this browser and that domain. | The name-to-IP-address process has been accomplished. Based on its results, the [[web browser]] points its request to the exact [[IP address]] in order to establish communication between this browser and that domain. | ||
Latest revision as of 21:58, 18 February 2019
On the Internet, any DNS resolver (alternatively known as Internet Service Provider's DNS resolver, ISP's DNS resolver, or, simply, resolver; hereinafter, the Resolver) is any server that (a) belongs to some Internet Service Provider and (b) moderates any process of translating (resolving) human readable hostnames into IP addresses that are used in communication between Internet hosts, or vice versa. The Resolvers are an essential part of Domain Name System (DNS).
The Resolvers receive requests in the form of a hostname from a web browser and request the needed data from root nameservers, which are the highest in the hierarchy, if the Resolvers haven't already cached that data. Indeed, the Resolvers not only redirect requests, but also cache the data needed to identify IP addresses.
Name-to-IP-address process
The complete name-to-IP-address process can be described in the following way:
- When the user enters a hostname (domain name) into a web browser, this browser queries their Resolver asking for the IP address.
- The Resolver asks the root nameserver where it can find details for that hostname, unless the resolver already has its IP address data cached.
- If it is asked, the root nameserver responds what TLD nameserver handles this data.
- The Resolver asks the TDL nameserver where it can find details for the entered hostname, unless it already has the data cached.
- If it is asked, the TLD nameserver responds that this data can be found at the host nameservers.
- The Resolver asks the host nameservers where it can find details for the needed IP address, unless it already has the data cached.
- If it is asked, the host nameservers have this data and respond with a DNS record containing the IP address for the entered hostname.
- The Resolver sends the identified data back to the web browser.
The name-to-IP-address process has been accomplished. Based on its results, the web browser points its request to the exact IP address in order to establish communication between this browser and that domain.
