An introduction to Domain Name System (DNS)
Domain Name System (DNS) is used to transfer the domain name into an IP address. The importance of transferring a domain name into an IP address is the system can understand only numbers. Every domain name has at least one IP associated with it. DNS implements a distributed database to store the name and the IP address over the internet. The DNS database resides on a special server. DNS works as client/server architecture. If the client’s request any information the DNS resolver will first contact the DNS server to determine the server’s IP address. If the DNS server does not have the required information the request will be forwarded to the next level until the request is completed. “Without DNS the internet is not useful or enjoyable”. So the Domain Name System is stated as “The Domain Name System (DNS) responsible for internet connection”.
DNS is similar to the contact app of your mobile. In mobile if you want to contact any persons you will make use of the number and not name. DNS works in the same way by associating a unique IP address with its domain.
What is Domain Name System (DNS) cache?
The DNS cache store local copies of recently accessed DNS records while the original continued to be remain on the designated server. The DNS cache helps to reduce the traffic. If the DNS cache is expired the network connectivity issue will arise.
How the Domain Name System works?
If the client enters the URL the browser will raise a query to the resolver. The resolver will ask the Root DNS. The Root DNS will find the name server within the top level domain. After mapping the top level domain the resolver will forward the query to domain name server. The domain name server will map the exact IP address of the domain with the help of the A record. The content of the domain name is displayed to the client.
Difference between Domain Name and IP address
IP address or Internet Protocol address is a unique number assigned to a system which is connected to the internet. The IP address is written in four numbers separated by periods. The current version of IP address is IPV4 and IPV6. IPV4 is 32 bit and it makes use of the numbers from 0 to 255 for e.g. 192.168.0.1. The IPV6 is 128 bit and it is based on hexadecimal.
A domain name is an information that you enter on the website to access a specific website. Since the IP address is tough to remember we make use of the domain name. The domain name is human friendly. The domain name has the name of the domain and Top Level Domains (TLD). For e.g. consider www.abc.com, in this example the domain is .abc and the TLD is .com
Hope the confusion between the domain name and IP address is cleared.
Domain Name System (DNS) Records
The Domain Name System has the following records
- Name Server
- MX Record
- TXT Records
The Name server is used to map the domain name to the available list of the DNS. Every domain name should have at least two name servers. This is because if one name server fails to map the Domain Name System the other name server will map the Domain Name System server. The root name server provides guidelines to all name servers. E.g. for Name Server Ns1.abc.com, Ns2.abc.com
There should be at least 2 name server to a domain name. You can have as much as name server you would like to have. The advantage of having multiple name servers is to avoid redundancy of the DNS. If the Name server is hosted on same network then there will be frequent traffic or downtime. So to avoid this, multiple name servers should be hosted in different network.
Name server record ensures that all the records are available at all the time. Hosting multiple name servers for a single website helps to overcome the network downtime.
The A record is used to point the correct IP address to the domain name from the domain name system. You may have single A record or multiple A record based on the records. One disadvantage of using A record is if the IP address of the target server changes then the A record will not point the correct domain name and IP address.
Here the domain name www.abc.com is pointed to the IP address 192.168.1.0.
An AAAA record is same as the A record. It is also used to point the domain name to the IP address but the AAAA record is used to point the IP address of version 6 (IPV6).
An MX Record is major component that helps an email message to reach its intended as a mail exchanger. An MX record is used to point the domains email to the mail server. To set up Gmail account with Google apps you need to point mx record to Google mail server. To overcome redundancy we can point more than one MX record to multiple servers.
With the help of MX record we can set priority level to the server. The priority is a number which simply choose the order of the mail recipients. For E.g. if priority is set to server1 as 0 and server2 as 1. The mail will be first sent to server1 and then to the server2.The mail server receives the mail from the user and forwards it to recipient or vice versa. E.g. for mail server: Sendmail, Exchange etc. The systems make use of the SMTP, POP and IMAP to send and receive mail.
CNAME stands for Canonical Name. It is used for pointing one host name to the other host name. It is just creating a duplicate for another domain name. The advantage of CNAME is domain can be forwarded to another server without changing any information in the designated server.
In the above example the domain name www.abc.com is pointed to another domain www.def.com. So if any user types www.abc.com he can see the content of the www.def.com. But the URL in the address will remain as www.abc.com.
The TXT record is plain text information added to the DNS servers. A TXT record has a domain name to which the text is assigned. The TXT record can be either machine readable or human readable. The Text record is used for implementing the SPF (Sender Policy Framework) records.
The SPF record controls the IP address and server to send an email. It is used in spam reduction. So if any unknown person tries to send email to your account the SPF will hold the mail and that email will not be forwarded to the designated email address.
|www.def.com||TXT||Located in server|
As a whole Domain Name System records play vital role in internet and it is responsible to run an internet smoothly.
Thanks for your interest. Hope the article provides you valuable information. If you have any queries about domain name system, please leave your comments below.