Definition of Domain Name Systems
The Domain Name System (DNS) is like a phone directory that resolves a URL (Uniform Resource Locator) name or website to its IP address. The URL address makes it easier for people to remember websites, while the IP address allows computers to communicate with each other. It is the job of the DNS to map these URL addresses to IP addresses by sorting through a hierarchical structure of vast domain names in the Internet.
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Importance
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DNS acts as the middle ground for users and computers to understand each other. It is similar to a language translator that translates information to the language that can be understood by the other. Without DNS, users would have a hard-time memorizing IP addresses of the websites. IP addresses are not very descriptive or informative--you would not know which website you're going to based on a string of numbers.
Structure
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The DNS is structured in a hierarchical manner to make it easier to locate websites in the Internet. When you type, for example, "www.example.com," the DNS initially looks at the root domain, which is the dot acting as separators between the words. The dot identifies which one is the top-level domain and which one is the secondary. DNS next looks at the top-level domain, which can be "com," "org," "net," "gov," "edu," "int," "mil" or any two-letter country code. These top-level domains have servers that manage each domain and the second-level domains registered in them. Once DNS identifies that "www.example.com" may be found in the "com" domain, it searches through the "com" name server to look for the second-level domain "example." If it finds it, it loads the website for you.
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Address Mapping
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The servers that run DNS contain a "host" file, which directly specifies that a certain URL address translates to a certain IP address. A website like Example.com has a server that categorically identifies the IP address linked to it. The DNS server has a look up option that forwards and queries other DNS servers for URL addresses it cannot resolve. You're able to access websites from any Internet-enabled device because one DNS server looks up another DNS server until it locates the URL address you're looking for.
Multiple DNS Servers
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Websites, especially those that generate a lot of traffic, have multiple servers for their domain name. This balances the load between all the servers to handle all Web requests. A URL address like www.example.com may be linked to several DNS servers with different IP addresses and your request to load the Web page is typically given to the DNS server with the least load. Having multiple DNS servers ensures that websites are accessible most of the time.
Other Functions
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DNS is a very powerful system, which acts as a great identifier and locator in the Internet. More than mapping IP addresses to URL names, DNS can also specify a mail server for the domain name. This allows emails to be received in the domain through its Mail Exchange (MX) record. DNS organizes the whole Internet system in such a way that information can be passed on and understood not just between computers but between users and computers.
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