Domain name resolution Overview

Domain name resolution Overview

Domain Name System (
DNS
,
Domain Name System
) Is used
TCP/IP
Distributed Database of applications, providing domain names and
IP
Address translation. Through the domain name system, users can directly use memory-friendly and meaningful domain names when performing certain applications, and the domain name resolution server in the network will resolve the domain name to the correct
IP
Address.

Domain name resolution is divided into static domain name resolution and dynamic domain name resolution, the two can be used in combination. When resolving a domain name, you must first use static domain name resolution (search for a static domain name resolution table). If the static domain name resolution fails, then use dynamic domain name resolution. Because dynamic domain name resolution may take some time and requires the cooperation of the Domain Name Server, some common domain names can be placed in the static domain name resolution table, which can greatly improve the efficiency of domain name resolution.

Static domain name resolution

Static domain name resolution is to manually create a Domain Name and
IP
The relationship between addresses. When a user uses a domain name for some applications (such
Telnet
Application), the system looks for the static domain name resolution table to obtain the corresponding
IP
Address.

Dynamic domain name resolution

Parsing process

Dynamic domain name resolution is completed by querying the Domain Name Server. The parsing process is as follows:

(1)
When a user uses a domain name for some applications, the user program first
DNS
The parser in the client sends a request.

(2) DNS
After receiving the request, the client first queries the local domain name cache. If a successfully resolved ing item exists
IP
The address is returned to the user program. If no ing item is found (
Dnsserver
) Sends a query request.

(3)
The Domain Name Server first looks for the corresponding domain name from its own database
IP
Address. If it is determined that the domain name does not fall within the scope of the domain name, the request will be sent to the domain name resolution server at the upper level for processing until the resolution is completed and the resolution result will be returned
DNS
Client.

(4) DNS
After receiving the Response Message from the Domain Name Server, the client returns the resolution result to the application.

 

User Programs,
DNS
The relationship between the client and the Domain Name Server, in which the parser and cache constitute
DNS
Client. User Programs,
DNS
The client is on the same device, while
DNS
Clients and servers are generally distributed on two devices.

Dynamic domain name resolution supports caching. The domain name and
IP
Address ing is stored in the dynamic domain name cache. When you query the same domain name, you can directly read it from the cache without sending a request to the Domain Name Server. Mappings in the cache area will be deleted after a period of time to ensure that the latest content is obtained from the domain name server in a timely manner. The aging time is set by the Domain Name Server,
DNS
The client obtains the aging time from the protocol message.

Domain name suffix list Function

Dynamic domain name resolution supports the domain name suffix list function. You can set some domain name suffixes in advance. During domain name resolution, you only need to enter some fields of the domain name. The system will automatically add different suffixes to the entered domain name for resolution. For example, you want to query the domain name aabbcc.com
You can configure COM in the suffix list first.
And then enter aabbcc
The system automatically connects the entered domain name and suffix to aabbcc.com.
.

When using the domain name suffix, the query method is divided into the following situations based on the way the user inputs the Domain Name: