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DNS Overview
A Domain Name System (DNS) is a distributed hierarchical system that converts hostnames to IP addresses. The DNS is divided into sections called zones. Each zone has name servers that respond to the queries belonging to their zones.
This topic includes the following sections:
DNS Components
DNS includes three main components:
- DNS resolver — Resides on the client side of the DNS. When a user sends a hostname request, the resolver sends a DNS query request to the name servers to request the hostname's IP address.
- Name servers — Processes the DNS query requests received from the DNS resolver and returns the IP address to the resolver.
- Resource records — Data elements that define the basic structure and content of the DNS.
DNS Server Caching
DNS name servers are responsible for providing the hostname IP address to users. The TTL field in the resource record defines the period for which DNS query results are cached. When the TTL value expires, the name server sends a fresh DNS query and updates the cache.
