DNS Server

[Saman]

You will learn about the DNS server configurations and overview, ip addressing, subnetting, domains description, how ip works. Domain name service is an Internet service that translates domain names into IP addresses. Domain names are easy to remember because they are alphabetic. On the other end, the internet is based on the IP addresses i.e every computer on the internet is associated with a unique IP address.

The communication on the internet is carried out on the basis of IP addresses and not on the domain names. A Domain name server service translates the domain name into its corresponding IP address for example the domain name robot.lk might be translated to 97.74.144.45. The DNS system is, in fact, forms its own network.

If one Domain name server doesn’t know to translate a domain name, it looks for another one and so on until the exact IP address is returned. DNS translates between the internet names and internet addresses.

How DNS Works
DNS organizes the hostnames in the form of hierarchy. A domain is a collection of of the sites that are related because they form a network (all computers that are geographically close as well. Universities are commonly grouped in .edu domain with each university or college using a separate sub domain.

While most of the topic does not require much technical knowledge, there is one technical part of the Domain name server.

When you type a name like example.com in your internet browsers it finds a way to map that name to the internet IP numbers, by which the internet easily reach the example.com computer. For this purpose your computer uses DNS of your Internet service provider company. All internet traffic work on these numbers and the important factor is that the looking up for the name is done by Domain name server.

That computer has a list of the host names/IP address mapping, which is regularly updated by the root DNS. Root DNS servers are the master servers that can help you look up any name. All the root DNS servers copy their own data from the one master server, which is under the control of ICANN. The root servers usually have a list that where you can look for the top level domains like .com, .net, org and .info etc. The ISP sends request for the particular domain name to the root sever and root server directs the request to the master server. In this way, you get the answer with your requested domain name.

IP routing and root servers

The domain lookups go to and from the root servers because main routers on the internet, ISPs and backbones have the list that where to find it.

Domains Description

.edu This domain name is used by the educational institutes like colleges and universities
.com This domain name is used by the commercial institutes/organizations and companies.
.Org This domain is used by the non-commercial organizations.
.net Administrative hosts, gateways and other networks.
.mil This is used by the U.S. military institutions.
.Gov This is used by the government institutes.
.info Used by the Informative sites.

There is a common question that how large is the internet and how Domain name server works. Domain name server simply provides mapping between hostnames and the IP addresses. When you dial in your ISP number and access it how does it get the answer in the form of requested domain name for you. It’s most likely that ISP may not have stored the information (requested site). In this case first the ISP server will send the query to the root-servers. These are the set of very high-powered servers that know all about the top level domains like .com, .org, .net, .info and all the country domains.

So, the ISP’s name server first contact with the root-servers. If the root-servers don’t have the requested information then redirect the request to the GTLD servers for any kind of top level domain and the answers come back to the ISP’s name servers with the requested information. At each step, ISP’s name server caching all the information. The Domain name server is central to the internet because without a domain name systems (DNS) its impossible to communication on the internet.