What are the main functions of the domain name system?

The domain name system is a distributed database that maps domain names and IP addresses to each other. Its main function is to provide domain name resolution services and resolve domain names into IP addresses, so that users only need to enter the domain name when accessing the website. functions that enable people to access the Internet more conveniently.

The main function of the domain name system is to provide domain name resolution services, resolve domain names into IP addresses, and enable users to access the website only by entering the domain name. Function.

The Domain Name System (DNS) is a system on the Internet that solves the problem of naming online machines. It is a service of the Internet. As a distributed database that maps domain names and IP addresses to each other, it can make people access the Internet more conveniently.

Domain Name System (DNS) uses TCP and UDP port 53. Currently, the limit on the length of each level of domain name is 63 characters, and the total length of the domain name cannot exceed 253 characters.

Domain name structure:

The Domain Name System (DNS) is composed of a resolver and a domain name server. A domain name server refers to a server that stores the domain names and corresponding IP addresses of all hosts in the network and has the function of converting domain names into IP addresses. The domain name must correspond to an IP address, and the IP address does not necessarily have a domain name.

According to the role played by the domain name server, the domain name server can be divided into four different types:

The domain name system adopts a directory tree-like level. structure. The domain name server is the server side in the client/server model. It mainly comes in two forms: main server and forwarding server. The process of mapping domain names to IP addresses is called "domain name resolution".

How the Domain Name System (DNS) works:

Step 1: The client makes a domain name resolution request and sends the request to Local domain name server.

Step 2: When the local domain name server receives the request, it first queries the local cache. If there is such a record, the local domain name server directly returns the query result.

Step 3: If there is no such record in the local cache, the local domain name server will directly send the request to the root domain name server, and then the root domain name server will return a queried domain (root domain name) to the local domain name server. The address of the primary domain name server for the subdomain).

Step 4: The local server sends a request to the domain name server returned in the previous step, and then the server that accepts the request queries its own cache. If there is no such record, the address of the relevant lower-level domain name server is returned.

Step 5: Repeat step 4 until the correct record is found.

Step 6: The local domain name server saves the returned results to the cache for next use, and returns the results to the client.

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