5.3.2. DNS Resolution

DNS translates human-readable names to IP addresses. Without DNS, users would need to remember IP addresses.

DNS Query Flow:

1. Client checks local cache
2. Queries configured DNS server
3. DNS server recursively resolves or forwards
4. Response returned and cached

Every DNS record carries a TTL (time to live, in seconds) set by the owner of the zone. Clients and resolvers may reuse a cached answer until its TTL runs out, which makes repeat lookups of the same name near-instant; it is also why a changed record can take up to its old TTL to be seen everywhere.

Common DNS Records:

• A: Name to IPv4 address
• AAAA: Name to IPv6 address
• MX: Mail server for domain
• CNAME: Alias to another name
• PTR: IP to name (reverse lookup)