What is DNS caching 5 and what is DNS caching

General domain name resolution.

The effective time is determined by the DNS server.

The impact of refresh time, the domain name is generally given by the provider to give a commitment to take effect within 24 hours, but it is often one or two hours to take effect.

This is for undertaking the Domain Name System.

Management, IP address.

A non-profit organization established for functions such as allocation, protocol parameter configuration, and master server system management.

ICANN has TLDs for different countries or regions.

These domain names are usually made up of two English letters. For example:UK stands for United Kingdom

fr stands for FranceJP stands for Japan. The top-level domain for China is:

cn，.The domain name under CN is managed by CNNIC. Trembling wide ants.

These hold all the information related to name resolution, and each information has an entry called TTL (Time to Live) where the data remains valid for a given amount of time. During this time, the corresponding queries are queried directly from the cache without the need to detour to the DNS service blocker.

Various applications, such as web browsers or name servers from internet service providers, also have their own DNS caches that are used to speed up name resolution.

DNS stands for Domain Name System.

It is a service of the Internet, and it is a bit difficult to understand what is DNS cache for newcomers to computers.

1. DNS cache means that after normal access to IP, the system will store this IP, and when accessed again, the system will directly extract and display the local DNS cache, which is equivalent to speeding up the resolution of **.

2. DNS records are stored in zone files and are used to convert domain names into IP addresses.

Also included is the domain name's server name and mail server information, such as the commonly used "www" in front of the domain name, which will also be listed in the DNS record.

3. Since the DNS record is composed entirely of text, it can be modified when needed. However, a single mistake can redirect the domain name to the wrong web server, which is why it is important to enter the DNS information accurately and double-check the change entries before saving the zone file.

4. How to clear DNS cache. Use the cmd command to modify, open the run in the computer, enter cmd in the input box, click OK, enter ipconfig flushdns in the window, press enter, and the DNS cache will be refreshed.

5. What are the benefits of eliminating DNS cache? Many people encounter a sudden can't access the Internet, at this time it may be that the DNS points to the wrong point, just clean up the DNS cache and reassign the IP.

That's it for what DNS caching is.

Method 1: Block DNS response messages sent without invitation.

A typical DNS exchange is made up of request information. The DNS resolver sends the user's request information to the DNS server, and after the DNS server processes the query request, the server returns the response information to the DNS resolver. However, it is important to note that the response message is not sent unsolicited.

Before the server receives the query request, the corresponding response information is generated, and the response is discarded.

Method 2: Discard fast retransmission packets.

1.Even in the case of packet loss, no legitimate DNS client will send the same DNS query request to the same DNS server at short intervals.

2.If the same query requests sent from the same IP address to the same destination address are sent too frequently, these request packets can be dropped.

But if you visit a certain ** many times in a short period of time, and the DNS has to be resolved and returned to you many times, you have all duplicated your work, right? So the operating system is very clever to design a local "DNS cache", when you access for the first time, the DNS returns the correct IP, the system will temporarily store the result, which is the DNS cache. And it will set an expiration time for the cache (e.g. n hours), within this n hours, when you access this ** again, the system will return the result to you directly from your computer's local DNS cache, without having to ask the DNS server, which in disguise "accelerates" the parsing of **.

Of course, after n hours, the system will automatically ask the DNS server again to get a new result.

So, if you change the DNS server and don't want your computer to continue using the previous DNS cache, you'll need to manually clear the local cache.