The DNS (Domain Name System) technology manages the websites domains names .A DNS Server is like a phone directory for internet i.e., it provides same service to the internet. When you type the domain name in the browser, the browser connects to the DNS server and checks for the IP address to which the domain name is registered and then displays the Website.
Private DNS servers:
Most of the DNS servers are private DNS servers. These servers allows you to have your own hosting services and can have accounts on your name.Private DNS servers are available for reseler, shared, cloud Hosting and dedicated users. These servers provide service only to those who own and configures them. For example XYZ and ABC have their own private servers, XYZ cannot use ABC servers and viceversa.
Public DNS servers:
Some of the companies provide free DNS servers which are available on net and these are called as public DNS servers. They provide service to who ever request them. Google, ScrubIt, dnsadvantage, OpenDNS these are the companies which provide public DNS servers.
2. ScrubIt Public DNS server address:
3. dnsadvantage free DNS servers:
Why is it important?
Generally it is really hard to remember numbers than names, remembering IP addresses of all the sites is highly impossible. This DNS server helps you in connecting the site’s domain name with its IP address.
For instance you want to open host department site, you don’t have to know its IP address you can just type host department in the browser and it will automatically get connected to its IP address 188.8.131.52. It is not at all possible to open a website with its name without DNS technology unless you know its IP address.
How does it work?
DNS Servers are arranged in hierarchy and they communicate with the help of a private network protocol. The servers that are placed at the top level are called as root servers. There are 13 root servers, these store all the internet domain names and their corresponding IP addresses. These severs are maintained by different agencies. Out of these 13 root servers 10 are situated in United States, 1 in Japan , 1 in Sweden and 1 in United Kingdom. Only these 13 servers store all the information and other servers which are at the low level of hierarchy,store information of certain departments or pieces of the whole existing database. These servers are maintained by Internet Service Providers. In DNS networking your web browser acts as a client and sends a request to your ISP’s DNS server and then the following process is followed.
- First when a user types a domain name in the browser say www.hostdepartment.com, the computer first checks the local DNS cache if it already has the website’s IP address (if already that website has been visited by the computer). If the name doesn’t match with the name then it performs a DNS query to get the IP address.
- If the information is not available locally then your computer sends a request to your ISP’s DNS server. These servers are recursive DNS servers and they are provided with their own caches and mostly the process end here and the information is received by the browser.
- In case if the information is not available then the request is sent to the next level servers that is to root name servers. These root servers don’t have the answer but they can direct you in a way where you can find the IP address of the domain name.
- The root servers reads the domain name www.hostdepartment.com and direct you to the TLD servers(Top Level Domain) for .com. Each TLD .com, .net, .org and so on has their own servers. These severs will not have the information but they directly direct us to the server which contains the information.
- The TLD servers checks the domain name www.hostdepartment.com and directs you to the .com specific server called authoritative servers. These servers will have all the information about the domain with .com, these information are stored in records. There are different types of records each record consists of different information. For instance if you want to know the address of a particular domain then it will check for the address record.
- The ISP’s recursive DNS server retrieves the information from the authoritative server and stores in the local DNS cache. When someone else requests for the same site then it directly checks in cache and send the information to the browser instead of going through all the process again.
- The record stored in cache have an expiry time, if the domain record expires then recursive DNS server requests for a copy so that the information is not out-dated.The recursive then sends the information to the computer, the computer stores the address in its cache and then sends address to the browser which makes a connection to the web server and opens the website. All these steps takes place in just milliseconds of time.