Thursday, 14 February 2013

What is DNS (Domain Name Server)

What is DNS (Domain Name Server)

DNS (Domain Name Server) is used to translate a domain name into IP address. This makes it possible for a user to access a website by typing in the domain name instead of the website's actual IP address. DNS is similar to a telephone directory.

Meaning of COM, NET, ORG etc.

COM -- commercial Web sites, though open to everyone
NET -- network Web sites, though open to everyone
ORG -- non-profit organization Web sites, though open to everyone
EDU -- restricted to schools and educational organizations
MIL -- restricted to the U.S. military
GOV -- restricted to the U.S. government
US, UK, RU and other two-letter country codes -- each is assigned to a domain name authority in the respective country

Domain Names should be unique

A registrar is an authority that can assign domain names directly and register them with InterNIC, a service of ICANN, which enforces uniqueness of domain names across the Internet. Each domain registration becomes part of a central domain registration database known as the whois database. Network Solutions, Inc. (NSI) was one of the first registrars, and today companies like GoDaddy.com offer domain registration and many domain management services.

How DNS (Domain Name Server) works?

1. If it has the domain name and IP address in its database, it resolves the name itself.

2. If it doesn't have the domain name and IP address in its database, it contacts another DNS server on the Internet. It may have to do this multiple times.

3. If it has to contact another DNS server, it caches the lookup results for a limited time so it can quickly resolve subsequent requests to the same domain name.

4. If it has no luck finding the domain name after a reasonable search, it returns an error indicating that the name is invalid or doesn't exist.
 
Registering a domain

Each domain name must have at least two name servers listed when the domain is registered. These name servers are commonly named ns1.servername.com and ns2.servername.com, where "servername" is the name of the server. The first server listed is the primary server, while the second is used as a backup server if the first server is not responding.

Name servers are a fundamental part of the Domain Name System (DNS). They allow websites to use domain names instead of IP addresses, which would be much harder to remember.

What is Parked Domain?

Using the DNS servers from your registrar or hosting company means that you have a parked domain. This means that someone else owns the computer hardware for the DNS servers, and your domain is just part of that company's larger DNS configuration.

What is Domain Propagation?

Domain Propagation is the period of time, or delay, involved in sending your domain’s address information to all the other name servers in the world. Name servers intentionally keep track of addresses for domains in their memory for a specific period of time which is defined by the administrator of the name server. This speeds up the process of looking up an address for a domain name. Unfortunately this “cached” information also stays in the name servers when it has been changed at the source of the original information (the domain’s registrar).

Name servers refresh themselves from once an hour to once a day. Generally 2-3 days time is a good estimate when a domain’s DNS information is changed at the domain registrar, after which everyone in the world can see the change.

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