What is dns
DNS stands for Domain Name System. It consists two components:
DNS server software and DNS Client. Client requests for the host name resolving and server does the same by translating the hostname to IP address. We need not to know the actual location of the machine where it is. The actual location might be changed from time to time but domain name will remain same. This works as a global directory of Internet.
Other Application of DNS:
Mail Server Agents also use DNS to find the particular address to deliver the e-mail. MX records also provides the location of the mail server where to deliver the e-mail.
Types of DNS records:
1. A records maps a hostname to 32 bit IPv4 address.
2. AAAA record maps a host name to 128 bit IPv6 address.
3. CNAME record stands for canonical name record used for aliasing the one name to many names.
4. LOC record specifies the physical location of the host.
5. MX record stands for Mail Exchange record maps a domain name to list of mail exchange servers of that domain.
6. PTR record maps an IPv4 address to canonical name of the host. This is reverse DNS lookup.
7. NS record ( name server record) maps a domain name to a list of DNS servers authoritative for that domain. Delegation is dependent on NS records.
8. SOA record ( start of authority record): This specifies the DNS server providing authoritative information about any internet domain, e-mail address of domain admin, domain serial number, and the timers relating to refreshing the zone.
9. SRV record stands for service location record. 10. NAPTR record stands for naming authority pointer. It supports regular expression based rewriting.
11. WKS record stands for well known service records. It gives the list of servers offering well known service like HTTP, FTP, POP3 etc.