The Domain Name System or DNS is the main part of internet which matches the domain name to the IP Address on which the website is hosted. This is done because it is not easy to remember the IP address. DNS also provides information about the domain names which commonly include Email Services. Without DNS the user will only be able to visit the visit through the IP address.
How does DNS Work
- The client enters the domain name www.yourcompany.com in the address bar of the browser. The client computer first checks its own DNS cache for this information. If Cache has been cleared or using the website for the first time it will not show the IP
- The query from the client computer is then redirected to the Internet Service Provider’s (ISP) DNS Server. The Internet Service Provider’s DNS server checks its own cache and it will not be there if accessed the domain name for the first time.
- The Internet Service Provider’s DNS server redirect the query to the Root DNS Server. Every DNS server will be having a file which contains a list of all the root DNS servers.
- The root DNS server keeps the information regarding top level DNS servers (.com .net .org etc) location and return the information to the Internet Service Provider’s DNS server.
- This will be further redirected to the Top Level DNS server (Nameserver). Each TLD (Top Level Domain .com .net .org etc) will be having its own name servers.
- The Top Level DNS server will be having information (DNS Record) about the IP for the domain name yourcompany.com and this information will be returned to the Internet Service Provider’s DNS server. Usually the A Name record (Address Record) will be having an Expiration value which directs to seek after the time.
- The Internet Service Provider’s DNS server redirects the query to the actual DNS server for yourcompany.com domain.
- The DNS server for yourcompany.com returns the IP address of the host of yourcompany.com to the Internet Service Provider’s DNS server.
- Then the ISP’s DNS server sends the IP address to the client computer to access the website at yourcompany.com
This whole process of working related to DNS happens in Milliseconds for completion.
ISP Blocking of Website
Just because a user is connected to internet does not mean that he have access to everything available over internet. Sometimes Internet Service providers block access to certain websites. Usually potentially illegal content are blocked. Web pages asking for user information without Privacy controls can also lead to blocking by ISP.
In such cases it can be accessed using the IP address of the website. This IP can be obtained by typing “tracert www.yourcompany.com” in the Command Window (Usually the First IP visible). Using proxy servers such websites can be accessed to see whether the ISP has blocked the website.
The DNS cache keeps a record of sites that you have recently visited on your computer. If that gets corrupted, you may have issues opening sites that were previously accessible without problems. If an unreachable website is in the cache, type ipconfig /flushdns in Run Command Box to clear the cache. In most cases the website will be visible after this.
Anti Virus and Firewall
Sometimes installing an External Firewall or Antivirus can block certain websites and disabling them and browsing can show up the website.