What is DNS resolution cache? Core principle and function detailed explanation

in daily network access, we can quickly open the corresponding web page by entering the URL, which is inseparable from the support of the DNS domain name system, and the DNS resolution cache is a key link to improve access efficiency. Many users may not be familiar with it, but always enjoy the smooth experience it brings. This article will disassemble the relevant knowledge of DNS resolution cache in an all-round way from the basic definition, core principle, practical function to maintenance skills to help everyone understand this important mechanism hidden behind the network.

What is the basic definition of DNS resolution cache?

to understand the DNS resolution cache in depth, we must first clarify its core definition and essential properties, which is the basis for understanding the subsequent content.

1, the core essence of DNS resolution cache

DNS resolution cache is a temporary database used to store the mapping relationship between the resolved domain name and the corresponding Internet Protocol Address in the DNS system. When a user accesses a domain name for the first time, the DNS server needs to go through multiple rounds of queries to obtain the Internet Protocol Address, and the DNS resolution cache will temporarily save the result. When the same user or other users visit the domain name again, they can directly retrieve the data in the cache without repeating the complete resolution process.

2, the existence form of DNS resolution cache

DNS resolution cache is not a single existence, it is distributed in multiple layers of the network. From the local cache of the user's end point device, to the cache of the router, to the cache of the operator's local DNS server, and finally the cache of the root name server, the cache storage time and coverage of different levels are different, and together build an efficient resolution acceleration system.

Second, the core operation principle of DNS resolution cache?

understand the operation principle of DNS resolution cache, we can understand how it can achieve network access acceleration, which is also the embodiment of its core value.

1, cache write trigger logic

when the DNS server completes a complete domain name resolution and obtains the Internet Protocol Address corresponding to the domain name, it will automatically write this mapping relationship to the DNS resolution cache, and set an expiration time for it, that is, the TTL value. The TTL value is set by the domain name manager, usually ranging from a few minutes to dozens of hours, which determines the storage time of the cache record in the server.

2, cache read priority

when a user initiates a domain name resolution request, the system reads the DNS resolution cache in order from near to far. First check the end point local cache, and return directly if there are valid records; if not, query the router cache, and then go up to the operator's DNS server cache until a valid cache record is found or a new resolution request is initiated. This priority order maximizes the shortening of the resolution path.

What are the actual functions of DNS resolution cache?

DNS parsing cache can become an important part of the network system, which is inseparable from its practical functions in many aspects, which directly affect the experience and efficiency of network access.

1, greatly improve network access speed

this is the most intuitive role of DNS resolution cache. When there is no cache, a domain name resolution may need to jump through multiple servers, which can take hundreds of milliseconds or even seconds, and it only takes a few milliseconds to retrieve the data in the DNS resolution cache, which can significantly improve the loading speed of web pages, especially for frequently visited websites.

2, effectively reduce DNS server load

tens of billions of domain name resolution requests worldwide every day, if each request initiates a complete resolution, the DNS server cluster will face huge load pressure. The existence of DNS resolution cache allows most repeated requests to obtain results directly from the cache, which greatly reduces the number of DNS server queries and ensures the stable operation of the entire domain name system.

3, optimize the stability of network access

when a DNS server at a certain level fails, the DNS resolution cache can play a temporary replacement role. If there are valid records in the local cache or the upper cache, the user can still complete the domain name resolution normally, and will not be directly disconnected due to a single point server failure, which improves the fault tolerance and stability of network access.

4. What are the maintenance skills of DNS resolution cache?

to make the DNS resolution cache continue to play the best effect, it is necessary to master the corresponding maintenance skills to avoid affecting the network access experience due to cache problems.

1, set the TTL value reasonably

domain name managers need to set the TTL value reasonably according to the update frequency of the website. For websites with stable content and little change in Internet Protocol Address, you can set a longer TTL value to make the DNS resolution cache last longer and improve the acceleration effect; for websites that frequently change Internet Protocol Address, you need to set a shorter TTL value to avoid users from being unable to access the latest server due to cache expiration.

2, regularly clean invalid DNS resolution cache

when the website changes the Internet Protocol Address, the old DNS resolution cache record will be invalid. If the user's end point or the cache in the server is not timely updated, the website cannot be accessed. At this time, the invalid cache needs to be manually cleaned. End users can clean the local cache through system commands, and server managers can refresh the cache through background operations to ensure the accuracy of the resolution results.

sum up, DNS resolution cache is an indispensable acceleration and stability mechanism in the network access process. The multi-level cache from the end point to the server builds an efficient resolution system, and improves the network access experience by shortening the resolution path and reducing the server load. Mastering its operation principle and maintenance skills can not only help us better enjoy smooth network services, but also quickly troubleshoot and solve related problems when they occur, giving full play to the core value of DNS resolution cache.