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DNS Queries

The DNS consists of a hierarchical set of name servers. Each domain or subdomain has one or more authoritative name servers that publish information about that domain. The hierarchy of authoritative name servers matches the hierarchy of domains. At the top of the hierarchy stand the root servers: the servers to query when looking up (resolving) a top-level domain name.

There are two types of queries that can be performed in DNS: Iterative and Recursive. A server responds to a iterative request with either the answer to the request or the name of another server that has the information or is closer to it. The requesting client must then iterate by sending a new request to this referred server, which again may either answer it or provide another server name. In the case of a recursive request, the server responds back with the answer if it has the information sought. Otherwise the server takes responsibility for finding the answer by sending requests to other servers.

In the animation you are able to select different scenarios and find out about how iterative and recursive querys from the loacal name server and the root server work.