DNS & ddns

DNS computer domain name system, composed of a parser and a domain name server;
DNS resolution process:

• First, search in the cache of the Local Computer; otherwise, send the request to the local DNS server;
• The local service is first searched in the local management area; otherwise, the local cache is searched;
• Unable to find locally, send the request to the local root domain name DNS server;
• After the root domain name DNS resolution, the request is forwarded to the next level of DNS, recursively until the target DNS server is found;
• The client receives the returned IP address, completes the request, and updates its own cache;

The DNS is encapsulated in the UDP message and the port number is 53.

Ddns is a remote domain name resolution, and the IP address bound to the domain name is dynamic.