DNS (Domain Name System)
Domain Name System converts host name or domain name into IP address and vice versa. It is equivalent to a phone book. It maintains a directory of domain names and converts them to IP addresses. The DNS assigns domain names and maps the names to IP addresses by designating an authorized name server for each domain.
Translating domain name to IP address:
Domain names are easy to remember for the people but the system access websites based on their IP address. So, it is necessary to convert the domain name to IP address. When a domain name is typed in the browser, Internet Service Provider views the DNS associated with the domain name and then translates it to IP address. Likewise, it is used to convert IP address to a domain name vice versa. Larger organizations use DNS to manage their own intranet. Home networks also use DNS for accessing the Internet.
DNS is based on client-server architecture. DNS clients send requests and receive responses from DNS servers. There are two types of lookups and they are forward lookup and reverse lookup.
- If the system converts the domain name to IP address, it is known as forwarding lookup.
- If the system converts IP address back to the domain name, it is known as reverse lookup.
These lookups are used to find correct servers to deliver Internet emails. The networks supporting DNS lookups runs over TCP and UDP port 53 by default.
DNS Cache is a temporary database that contains the records of all recent visits and attempted visits to websites and other Internet domains. It stores all the local copies while the originals will be maintained in the designated servers. It helps to avoid network traffic but if a DNS becomes outdated, network connectivity issues can happen. DNS Caches are easily prone to attack by hackers and it can be easily flushed by network administrators using ipconfig and other similar utilities.
Dynamic DNS adds network protocol extensions to DNS. It is used to enable name resolution service for dynamic clients. It also supports dynamic IP addresses which are suitable for home networks as it normally receives dynamic public IP addresses from their Internet provider which changes occasionally.