The DNS is a hierarchical distributed naming system that associates domain names with IP addresses. It automatically converts domain names typed into web browsers to the corresponding IP addresses of web servers hosting those sites. A fully qualified domain name (FQDN) contains all domain name labels from most specific to most general to uniquely identify a host, such as challenger.atc.fhda.edu. Generic top-level domains are three or more characters long and country domains use two-character ISO country codes. The DNS mapping of names to addresses is performed by independent, cooperative name servers that hold master or copy databases.

1. Domain name system
Prepared By: Assi. Professor Sejal Jadav

2. Q- Domain name system

3. • DNS is an abbreviation for Domain Name System
• The Domain Name System (DNS) is a hierarchical distributed
naming system for computers, services, or any resource
connected to the Internet or a private network.
• It associates various information with domain names assigned
to each of the participating entities.
• DNS automatically converts the names we type in our Web
browser address bar to the IP addresses of Web servers hosting
those sites.

4. Full Qualified Domain Name (FQDN)
• If a label is terminated by a null string, it is called a fully
qualified domain name (FQDN).
• An FQDN is a domain name that contains the full name of a
host.
• It contains all labels, from the most specific to the most
general, that uniquely define the name of the host.

5. • Example: challenger.atc.fhda.edu.
• For example, the domain name is the FQDN of a computer
named challenger and
Installed at the Advanced Technology Center (ATC) at
De Anza College.
• A DNS server can only match an FQDN to an address.
Generic Domain:
• The top level names are called the generic top-level domains,
and can be three characters or more in length.
• Below table shows some of the top level domain .

7. Country domain:
• There are also top-level domains named for the each of the
ISO 3166 international 2-character country code.
• These are called the country domains or the geographical
domains.
• The mapping of names to addresses consists of independent,
co-operative system called name servers.
• A name server is a server program that holds a master or a
copy of name-to—address mapping database.