Domain Name System (DNS)
The domain name systems main function is to translate a human readable domain name into an IP address. It is in essence a massive distributed database across many server. This distributed database uses different DNS records and a hierarchy of servers.
- Root DNS servers: There are 13 mainly located in North America which are a network of replicated servers.
- Top level domain (TLD) server: These are responsible for top level domains such as .com, .org, ect.
- Authoritative servers: An organisations DNS server that control their domain.
- Local DNS (LDNS) servers: This can be owned my users or ISPs and act as a proxy to the root servers.
When querying DNS servers requests can either be iterative meaning that the host that sends them keeps getting back another location to go to or recursive which means the host requested for the information goes directly to the next server. An example of a typical request can be seen below.
DNS servers also offer other services such as:
- Mail server,
- Load distribution,
- Certificate authorisation,
- Others that can be found in the DNS records.