WHAT IS DNS?

WHAT IS DNS?

DNS Stand for DOMAIN NAME SYSTEM, People prefer to use easy-to-remember names instead of IP Addresses, Domain names are alphanumeric names for IP addresses e.g., www.Microsoft.com, www.google.com.

The domain name system (DNS) is an Internet-wide distributed database that translates between domain names and IP addresses.

Domain Name System are usually used to translate a hostname or Domain name (Ex. microsoft.com) into an IP address (Ex. 131.107.0.89). Domain name comprise a hierarchy so that names are unique, yet easy to remember.

DNS makes it possible to refer to the Internet protocol(IP) based system(hosts) by human friendly names (domain names). Name resolution is that act of determining the IP address of a given hostname.

Two Benefits of DNS

      1)      Domain Name can be logical and easily remembered.

      2)      should an IP address for a host change, the domain name can still resolve transparently to the users or application.

DNS name resolution is a critical Internet service. Many network services require functional name service for correct operation.

Label	Description
Com	Commotional origination
Coop	Cooperative Business Origination
Edu	Education institutions
Gov	Government institutions
Info	Information Service provider
Int	International origination
Mil	Military groups
Museum	Museum and other nonprofit origination
Name	Personal name (individual)
Net	Network support center
Org	Nonprofit origination
Pro	Professional nonprofit origination
Aero	Airline and aerospace companies
Biz	Businesses or firms

1. Domain Name System

DNS is a large network of servers located across the globe that contain a distributed database of domain names and IP addresses. Often referred to as the Internet’s address book, DNS connects domain names to IP addresses. So, when you type in a site’s URL into your browser, the DNS will find the IP address that matches the domain name. Your browser can then contact the right server and retrieve the website and its content.

2. IP Address

An IP address is a unique group of numbers, separated by full stops. Each computer and server that uses the Internet has its own IP address, and this enables computers to communicate over the network. As computers deal in numbers, it makes sense that computers are identified via IP addresses. But for humans, remembering a string of numbers each time you want to visit a website just doesn’t work. That’s where domain names come in.

3. Domain Name

A domain name is the name of your website (Ex.google.com). Domains can be purchased through a domain registrar, or are often provided for free through your hosting provider. Without domain names, to open a website you would need to remember and type in a site’s IP address Using domain names makes visiting websites quick and straight forward and gives the process a human approach by using words instead of numbers.

Fully Qualified Domain Name

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. For example, the domain name www.microsoft.com. is the FQDN of a computer named Microsoft installed at the NEC Collate. A DNS server can only match an FQDN to an address. Note that the name must end with a null label, but because null means nothing, the label ends with a dot (.).

Partially Qualified Domain Name

If a label is not terminated by a null string, it is called a partially qualified domain name (PQDN). A PQDN starts from a node, but it does not reach the root. It is used when the name to be resolved belongs to the same site as the client. Here the resolver can supply the missing part, called the suffix, to create an FQDN. For example, if a user at the Microsoft.com. site wants to get the IP address of the challenger computer, he or she can define the partial name server1.

The DNS client adds the suffix Microsoft.com before passing the address to the DNS server. The DNS client normally holds a list of suffixes. The following can be the list of suffixes at NEC College. The null suffix defines nothing. This suffix is added when the user defines an FQDN.

Generic Domains

The generic domains define registered hosts according to their generic behavior. Each node in the tree defines a domain, which is an index to the domain name space database.

Country Domains

The country domains section uses two-character country abbreviations (e.g., np for Nepal and us for United States). Second labels can be organizational, or they can be more specific, national designations.

Inverse Domain

The inverse domain is used to map an address to a name. This may happen, for example, when a server has received a request from a client to do a task. This type of query is called an inverse or pointer (PTR) query. To handle a pointer query, the inverse domain is added to the domain name space with the first-level node called arpa (for historical reasons). The second level is also one single node named in-address (for inverse address). The rest of the domain defines IP addresses.

DNS Process

DNS follows a strict process when performing a query. The process is as follows.

1. The local DNS cache on the host is queried first.

2. If there is no entry in the local cache, the local HOSTS file is queried next.

3. If there is no entry in the local HOSTS, the query is forwarded to any configured DNS servers on the host. If no DNS servers are configured, the query will fail.

4. If the configured DNS server is not authoritative for that domain, and does not have that DNS entry locally cached, the query will be forwarded up the DNS hierarchy. DNS servers can be configured with one or more forwarders. Organizations often point to their ISP’s DNS servers for DNS forwarding purposes.

5. If no forwarders are available, the query is forwarded to the Root DNS server(s), which will likely have the entry cached.

6. In the rare circumstance that the Root servers do not have a cached entry, the query will be forwarded back down the hierarchy to the authoritative DNS server for that domain.