Networking · Notes
DNS basics
DNS translates names into information such as IP addresses. A typical lookup passes through a recursive resolver, which may answer from cache or contact authoritative servers.
The usual path
application
↓
recursive resolver
↓
root
↓
TLD
↓
authoritative server
↓
cached answer
TTL and caching
A DNS record normally includes a TTL. Resolvers may reuse the cached answer until that interval expires, which is why DNS changes are not always visible everywhere at the same moment.
Common records
A and AAAA map names to IPv4 and IPv6 addresses. CNAME creates an alias, MX describes mail routing, while TXT is commonly used for ownership and policy information.