IWT | Why do you mean by domain name system? Explain it with related structure.

DNS is a host name to IP address translation service. DNS is a distributed database implemented in a hierarchy of name servers. It is an application layer protocol for message exchange between clients and servers.

There are various kinds of DOMAIN:

1.    Generic domain: .com(commercial) .edu(educational) .mil(military) .org(non-profit organization) .net(similar to commercial) all these are generic domain.

2.    Country domain .in (India) .us .uk

3.    Inverse domain if we want to know what is the domain name of the website. Ip to domain name mapping. So, DNS can provide both the mapping for example to find the IP addresses of eresjournals.org then we have to type lookup www.eresjournals.org.

DNS record – Domain name, ip address what is the validity?? what is the time to live ?? and all the information related to that domain name. These records are stored in tree like structure.

Namespace – Set of possible names, flat or hierarchical. Naming system maintains a collection of bindings of names to values – given a name, a resolution mechanism returns the corresponding value –

Name server – It is an implementation of the resolution mechanism. DNS (Domain Name System) = Name service in Internet – Zone is an administrative unit; domain is a sub tree.

Root name servers – It is contacted by name servers that cannot resolve the name. It contacts authoritative name server if name mapping is not known. It then gets the mapping and return the IP address to the host.

Top level server – It is responsible for com, org, edu etc and all top-level country domains like uk, fr, ca, in etc. They have info about authoritative domain servers and know names and IP addresses of each authoritative name server for the second level domains.

Authoritative name servers This is organization’s DNS server, providing authoritative host Name to IP mapping for organization servers. It can be maintained by organization or service provider.