DNS Domain Name Service - an Introduction
In this article, we get introduced to DNS Domain Name Service and what role it plays in data communication over a network. Knowledge of how DNS works is crucial to the subject of networking and also in understanding how resources are accessed off a network.
Domain Name Service (DNS) is the most widely used network service today. Most users connect to a resource on the internet by using a friendly name, such as www.techulator.com - which is commonly known as a FQDN (Fully Qualified Domain Name). A resource can only be accessed once it's IP address is known, and thus DNS performs the all critical task of resolving the FQDN to it's respective IP address, so that the particular resource can be accessed.
A step by step process that takes place while resolving a name can be something similar to what is described below:-
1. Let's say that you are at your office and are trying to connect to www.techulator.com
2. The client computer sends a query to the local DNS server at the office to check if it has the IP address for the resource being accessed
3. The local DNS server does not have the IP address (if the resource is being accessed for the first time), and so it sends a query over the internet to a DNS root server (which would be located somewhere on the internet)
4. The root DNS server will forward the query to a Name Server (also known as a Top-Level Domain Server) that would be located at the next level down, which in this case would be the .com name server
5. The top level Name Server then forwards the query to the "techulator.com" Name Server where there will be an existing record having the IP address of this resource
6. The local DNS server thus retrieves the IP address of the resource and saves the same in it's cache for future accessTop Level Domains
The root DNS servers are responsible for forwarding a DNS request to the appropriate Top-Level domain. DNS always finds the requested IP address by reading the FQDN from right to left, so while reading www.techulator.com, .com is the far right name part, and so the DNS query will be forwarded to a .com top-level domain name server. Top-level domains were created to better organize the DNS distributed database on the internet, and every individual or organisation that needs a web site, has to register under a top-level domain.
Some of the most popular top-level domains found on the internet are as below:-
.com : This is mainly the commercial organisations group and is by far the largest, most common top-level domain of the internet. Almost everyone wants to be registered in this domain as it is the most searched domain by people trying to find a resource.
.org : This domain is mainly used by non-profit organisations.
.net : This domain is mainly for networking organisations and/or Internet service providers.
.gov : This domain is mainly used by government organisations.
.edu : This domain is mainly used by educational organisations. Country Domain Names
With a limited number of top-level domains available for individuals and organisations to register, it soon became a problem as there were too many names to register and ver few top-level domains to choose from. Top-level domains were thus created for countries, wherein an individual or organisation could register for a domain in their specific country, thereby allowing users to easily find them. Some common country domain names are as under:-
.in : India
.ca : Canada
.ie : Ireland
.uk : United Kingdom
.us : United States DNS Files
Every DNS server maintains it's DNS data/records in a number of files that exists on the hard disk of the server. In the old days, the records would be managed by updating text files, but today there are graphical tools that let an administrator manage the DNS records on a server. Windows servers store their DNS files in %SystemRoot%\system32\DNSHOSTS File
Before DNS became a solution to hostname resolution, there existed a more manual method of creating and modifying a file on the local hard drive of every system. This file was known as the HOSTS file and contained a list of FQDN's along with their respective IP addresses. This file would be stored locally on every system and on windows machines it would be stored at %SystemRoot%\system32\drivers\etc, and contains two columns - one for the IP address and the other for the corresponding FQDN Windows Internet Naming Service (WINS)
The Windows Internet Naming Service (WINS) provides name resolution for NetBIOS names to corresponding IP addresses, and is quite popular on large Microsoft networks. WINS is similar to DNS, but contains a database of different style names - NetBIOS names instead of FQDN's.
When a WINS client boots up, it registers itself with a WINS database, and then that database is queried whenever a computer's name needs to be resolved to an IP address. Every running system on the network thus have the ability to communicate with each other. When the client shuts down, it de-registers itself with the database.
Before WINS, the LMHOSTS file was used to assist in resolving NetBIOS names to IP addresses. The LMHOSTS is a static file that maps NetBIOS names to IP addresses, and is very similar to the HOSTS file in functionality, but the only difference being that LMHOSTS maps NetBIOS names to IP addresses, whereas HOSTS maps FQDN's to IP addresses.
Read How to get a .com domain at just Rs 99 per year on GoDaddy
DNS means Domain name Server or Domain name system.DNS helps to convert the ip address into domain name.Domain name into ip
address.You cannot remember many website ip address at same time.So domain name is used for remembering the website.
For example 74.125.239.17 is one ip address of Google.com.It is very difficult to remember always.So you can use domain name to view the particular website.The primary work of DNS is if you give ip address in browser ,it search for domain name of particular ip address.If you give domain name in the address bar of the browser it convert the domain name to ip address . If you have any queries regarding DNS records use http://www.whoisxy.com/dns-query.aspx .