DNS servers play a fundamental role in Internet browsing, and have an important influence on the speed and performance of your access to the network. The use of some or other servers, their modification, or the dangers of using the wrong DNS servers are some of the aspects you should know about. In fact, DNS servers are one of the fundamental pieces in the chain that is carried out when we make a web request to any of the portals we visit.
A DNS server, also known as a name server, consists of server software that uses a DNS database to respond to requests that are related to the domain namespace. As, as a rule, they are hosted on dedicated hosts, they are also referred to as the computers that host these programs. There is usually a differentiation between primary and secondary DNS servers:
- Primary, primary or master server: A primary or master DNS server is called when it stores information about a specific area of the domain name space in its own database. The domain name system is built in such a way that each zone has at least one primary name server. A system of this type is usually implemented as a cluster of servers where the identical zone data is stored in a master system and in several slaves, increasing, thanks to this redundancy, the security against falls and the availability of a master server. From here comes the name of primary and secondary servers that has been used.
- Secondary or slave server: when the information of a name server does not come from the own zone files, but are second or third-hand, this server becomes secondary or slave for this information. This situation occurs when a server cannot resolve a request with its own database and has to resort to the information available in another name server (recursive resolution). This DNS data is stored temporarily in a local storage (caching) and is provided in case of future requests. As it is possible that the entries in the zone file itself have changed in the meantime, the information provided by secondary servers is not considered secure.
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Functions of DNS servers
Resolution of names
It consists of returning the IP address that corresponds to a domain. Internet sites and services are identified by their numeric IP addresses, almost impossible to memorize by humans.
For that reason, domain names were created. When making the request to the browser of an address, it accesses the nearest DNS, which returns the IP corresponding to the requested site. For example, when clicking on the link https://web3mantra.com/, we must wait (some milliseconds) for the request to travel to the default DNS of the connection and return the result.
Only then can the browser request the indicated page from this site. Of course after that, this relationship is saved in the cache for a while, to speed up subsequent queries.
Inverse address resolution
It is the reverse mechanism to the previous, from an IP address get the corresponding host name.
Resolution of mail servers
Given a domain name (for example gmail.com), obtain the server through which the delivery of the email must be made.
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