What is a Domain Name Server?

By

Cosmo

|

Aug 28 - 2014

StarterGuide:

What is a domain name server ?

We have introduced the concept of internet protocol (IP) addresses in ourstarter guide to web hosting. Let's move on to the technological infrastructure that is actually responsible for translating the IP addresses of websites into human-friendly domain names that we can easily remember.


Domain name servers translate IP addresses (the numbers) into domain names (words) that cab be easily remembered.


Data Exchange on the Internet

Data transmission across the Internet would not be possible without the use of communications protocols such as the Transfer Control Protocol/Internet Protocol (commonly abbreviated to TCP/IP). The TCP/IP protocol are a set of rules which determine how data is exchanged between different machines on the Internet. A simple analogy would be that an Internet Protocol (IP) assigns the location or address of a machine on the Internet and the TCP is the protocol that actually establishes the connection between such machines for data exchange.


Without such protocols, every machine on the Internet would require a direct connection with one another in order to have data transferred between them.


The Domain Name System

The problem with IP addresses however is that they are in a machine-readable format which is expressed in a series of numbers that is not meant to be used by humans in this numerical form. As more and more domains were being created, it was also correspondingly more difficult to keep track of all their IP addresses.


Recognizing this problem in 1983, Paul Mockapetris and Jon Postel, at the University of California, invented the Domain Name System - a system of assigning domain names to websites and servers instead of using IP addresses. In his seminal RFC (Request for Comment) 882 document, Paul explains the conundrum :


RFC 882 - The Need for Domain Names

The ARPA Internet illustrates the size-related problems; it is a large system and is likely to grow much larger. The need to have a mapping between host names (e.g., USC-ISIF) and ARPA Internet addresses (e.g., 10.2.0.52) is beginning to stress the existing mechanisms. Currently hosts in the ARPA Internet are registered with the Network Information Center (NIC) and listed in a global table (available as the file HOSTS.TXT on the SRI-NIC host).


The size of this table, and especially the frequency of updates to the table are near the limit of manageability. What is needed is a distributed database that performs the same function, and hence avoids the problems caused by a centralized database.

RFC 882


ARPANET is considered the predecessor of the modern Internet and was used by the U.S. Department of Defense for its projects conducted at universities and research laboratories. Before there were millions of domains, researchers used to store IP addresses in simple text documents like the HOSTS.TXT mentioned above.


The architecture underpinning the DNS is fairly technical and is probably beyond the interests of most people. Briefly, it works by using a system of special servers to translate and match IP addresses to their respective domain names. Now all you have to remember are domain names instead of IP addresses.


If you are interested in learning more about the this subject, you can check out Harvard's Berkman Center for Internet and Society's page on thebrief historyof the Domain Name System and Paul's importantRFC 882that started it all.


The Domain Name System is managed and coordinated by theInternet Corporation for Assigned Names and Numbers(or ICANN). ICANN is a non-profit organization that keeps track of all registered domain names and also ensures that every IP address on the Internet is unique and correctly maps to their respective domain names and vice versa.


Domain Name Servers

The Domain Name System works by using a wide network of specialised web servers called domain name servers (DNS servers or name servers) to map unique IP addresses to their corresponding domain names.


A name server is a server registered with ICANN to participate in the Domain Name System and contains a directory of domain names as well as addresses for other name servers. Typically, they accept requests from web users and other name servers to translate domain names into IP addresses to look for a requested website.


When a request is made to a name server, it can perform one of the following actions :

  • It can answer the request by providing the requested IP address if it is in it's own database.

  • It can contact another name server to find the IP address for the domain name requested which it may have to do multiple times across a number of other servers unitl the domain name is located.

  • It may return an error message if the requested domain name cannot be found or does not exist.

Name servers are some of the busiest web servers on the Internet processing billions of requests at any given time. While all this is happening, many more IP addresses/domains are being added each day. The latestDomain Industry Briefby Verisign states there are over 270 million domain names in existence as of 31 March 2014.


They cope with this immense task by using a distributed system of DNS servers to essentially function as a single integrated database of IP addresses.


Conclusion

The Domain Name System is what is used to translate IP addresses into its respective domain names and vice versa. The translation and mapping is done with the aid of a wide network of DNS or name servers throughout the world.


Next we will look at what aDomain Name Registraris and how it fits into the architecture of the Domain Name System described above.



In a

nutshell

1.

Every domain name or website on the Internet has its own unique IP address.

2.

IP addresses are in a machine-readable numerical format that is hard for humans to use. Domain names which are textual representation of these IP addresses are much more intuitive and easier for us to remember than a series a numbers.

3.

An approach called the Domain Name System was developed to address the inconvenience of using IP addresses by translating them into domain names that we still use today.

4.

The Domain Name System is maintained by the Internet Corporation for Assigned Names and Numbers (ICANN) and is implemented through a wide distributed network of domain name servers.

5.

A domain name server has a database of IP addresses and domain names. Domain name servers are in turn maintained by a number of called domain name registrars.



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