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This article mainly explains "what does TTL refer to in domain name resolution". The content in the article is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what does TTL mean in domain name resolution"?

We often see the TTL field when we resolve the domain name, which is 3600 by default. In addition, sometimes we PING a domain name or IP, there will be TTL= XXX, so what exactly does TTL mean?

What is the TTL value of a domain name?

TTL (Time-To-Live) is the retention time of a domain name resolution record in the DNS server. When the local DNS server receives the resolution request, it will send the resolution request to the NS server specified by the domain name to obtain the resolution record. After obtaining this record, the record will be saved in the DNS server for a period of time. If the resolution request for this domain name is received again during this period, the DNS server will no longer issue a request to the NS server, but will directly return the record just obtained. The time this record is kept on the DNS server is the TTL value.

Application of TTL value setting:

one。 Increase the TTL value to save domain name resolution time and speed up website access.

In general, the various records of domain names are rarely changed and are likely to remain unchanged for months or years. We can increase the TTL value of the domain name record to make the record cache longer in the local DNS server, so that when we visit this website over a longer period of time, the DNS server of the local ISP does not need to issue a resolution request to the NS server of the domain name, but returns the domain name resolution record directly from the cache.

The TTL values of many domestic and international platforms are measured in seconds, and many default values are 3600, that is, the default cache is 1 hour. This value is really a little small. Will someone change the domain name record every hour? You can expand this value appropriately according to your needs, such as setting it to 86400 if you want to cache it for one day. Godaddy's TTL setting is straightforward, but there are only five values that can be selected, and it's a bit rigid to switch to advanced setting mode immediately. The website is profitable

Forced by the environment, the LifeTyper.com TTL value is set to a maximum of 1 week, and setting it to a higher value may have unnecessary trouble writing. For example, when you want to change the space, these old records will take a long time to expire and be updated.

two。 Reduce the TTL value and reduce the inaccessible time when changing the space.

99.9% of the replacement space will have the problem of DNS record changes, because of cache problems, the new domain name record may take effect in some places, but in some places it may take a day or two or more to take effect. The result is that some people may have access to the new server, and some people may have access to the old server. Just visiting, it's not a big deal, but when it comes to sending mail, it's a bit of a hassle, and maybe some important letter will be sent to the old server that has been stopped.

In order to minimize the parsing time difference between different places as much as possible, it is reasonable to:

1. First check the current TTL value of the domain name, which we assume is 1 day.

two。 Change the TTL value to the minimum value that can be set, and if possible, it is recommended to be 1 minute, which is 60.

3. Wait a day to make sure that DNS server caches everywhere are expired and records are updated.

4. Set and modify new records, and at this time, DNS from all over the country can update to new records as quickly as possible.

5. After confirming that the DNS has been updated everywhere, set the TTL value to the value you want, and the TTL=60 is still a little too small.

Remember, all this works on the premise that those DNS servers fully comply with these standards and specifications, otherwise how to set up TTL on NS servers will be in vain, but so far no such unruly DNS servers have been found.

The problem is that there are no real high-speed NS and DNS servers. As mentioned here, Wanwang, which performs well at home, has a low score in foreign evaluation websites, while Godaddy, which gets the highest score in foreign evaluation, is not much faster than Wanwang in China. If you have the money to deploy a large number of CDN acceleration servers and NS servers around the world like Google and Microsoft, of course, the problem is that this is impossible for most websites. It is not impossible to have both at home and abroad, but it is very difficult for websites to make a profit.

Some people may think that you can improve the resolution speed by assigning two NS records to the domain name (one domestic and one foreign), but this is also impossible. Only when the DNS server fails to get the record from the first NS server will the resolution request be sent to the second NS server. One of the cheapest and most effective ways I know to speed up is to modify the TTL value of the domain name record mentioned above.

Thank you for your reading. the above is the content of "what does TTL refer to in domain name resolution". After the study of this article, I believe you have a deeper understanding of what TTL refers to in domain name resolution, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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