What is domain name caching? Detailed explanation of core concepts and principles

in daily network access, we can quickly open the corresponding website by entering the domain name. This process is inseparable from the support of DNS resolution, and domain name caching is the key technology to improve the efficiency of resolution. Many users understand this technology only on the surface. This article will deeply dismantle the core definition, operation logic, actual value and optimization method of domain name caching to help everyone fully understand this important mechanism hidden behind network access and understand how it affects our online experience.

What is the core concept of domain name cache?

to understand the role of domain caching, we must first clarify its essential definition and core properties.

1, the basic definition of domain name cache

domain name cache is a temporary storage mechanism in the DNS resolution system. It stores the mapping relationship between the resolved domain name and the corresponding Internet Protocol Address in a specific network node or local device. When a user visits the same domain name again, the system can directly retrieve the mapping information from the cache without reinitiating a complete DNS resolution request, thus shortening the resolution time.

2, the core attributes of the domain name cache

domain name cache has two core attributes of timeliness and hierarchy. Timeliness means that the cache content has a fixed expiration time, which is determined by the TTL value. After the expiration, the cache will be automatically cleared, and the system needs to restart the resolution; hierarchy means that the cache is distributed in multiple layers from local devices to top-level DNS servers, and there are differences in cache coverage and update frequency at different levels.

What is the function of domain name cache?

understand the core concepts, then we dismantle the specific operation process and key logic of the domain name cache.

1, domain name cache trigger logic

when a user accesses a domain name for the first time, the system will initiate a complete DNS resolution request, starting from the local DNS server and recursively searching up until the corresponding Internet Protocol Address is obtained. After the resolution is completed, each network node participating in the resolution will automatically store the mapping relationship between the domain name and the IP in its own domain name cache to prepare for subsequent repeated visits.

2, domain name cache call process

when the user visits the same domain name again, the system will prioritize the query domain name cache from the local to the superior. First check the cache of the local device, if there is a valid mapping, use it directly; if the local cache is invalid or does not exist, query the domain name cache of the local DNS server; if it is still not found, a recursive resolution request will be initiated, and the whole process greatly shortens the resolution waiting time.

What are the core functions of domain name caching?

domain name cache is not a meaningless technical setting, it plays multiple key roles in the network system.

1 Reduce DNS resolution latency

this is the most intuitive role of domain caching. Complete DNS recursive resolution usually requires multiple node queries, which can take hundreds of milliseconds, while calling the mapping information in the domain name cache only takes a few milliseconds, which can significantly reduce the time for users to wait for web pages to load and improve the smoothness of network access, especially for frequently visited websites.

2, reduce DNS server load

if every domain name visit initiates a new resolution request, the top-level DNS server and authoritative servers at all levels will bear huge query pressure. Domain name cache can intercept most of the repeated resolution requests in the local or lower nodes, reduce the number of queries initiated to the higher-level server, thereby reducing the load of the entire DNS system and ensuring the stability of the resolution service.

3, improve network access stability

when a DNS server fails or the network link is interrupted, the effective mapping information in the domain name cache can be used as a backup resource, so that the user can still complete the mapping of the domain name to IP through the cache, to avoid the situation that the website cannot be accessed, and to some extent, the fault tolerance of network access is improved.

What are the common levels of domain name caching?

domain name cache is not stored centrally in a single node, but distributed in different network layers, each level of cache has its own unique positioning.

1, local device domain name cache

This is the closest to the user's domain name cache level, stored in the user's computer, mobile phone and other end point devices. The coverage of the local cache is only the current device, the TTL value is usually short, and the update frequency is high. It is mainly used to accelerate the repeated access of the same device to the same domain name. Users can manually clear the local domain name cache through system settings.

2, local DNS server domain name cache

local DNS server is usually set up by operators or enterprises, and its domain name cache covers all users under the same network. The cache TTL value of this level is long, which can provide resolution services for a large number of users and effectively reduce the query requests of users' end points to the superior server. It is a key node in the domain name cache system.

3, authoritative DNS server domain name cache

authoritative DNS server is responsible for storing the official mapping information of a specific domain name, and also caches other domain name information that has been resolved by itself. This type of domain name cache is mainly used to handle recursive query requests from lower-level servers, further reducing queries to top-level DNS servers, and ensuring the efficient operation of the entire DNS system.

What are the optimization methods of domain name cache?

to maximize the value of domain name cache, it needs to be optimized through scientific configuration and management.

1, set the TTL value reasonably

TTL value determines the effective duration of the domain name cache. If the setting is too long, the domain name resolution update may not be timely. If the setting is too short, the role of the domain name cache cannot be fully exerted. For websites with relatively stable content, a longer TTL value can be set, such as 24 hours; for dynamic websites that often change IP, a shorter TTL value should be set, such as 15 minutes, to balance cache efficiency and update timeliness.

2, regularly clean invalid cache

Although the domain name cache will automatically expire, in some special cases, such as after the website changes the IP, there may be a situation where the domain name cache of some nodes is not timely updated. At this time, it is necessary to manually clean the invalid cache of the relevant nodes to ensure that users can obtain the latest IP mapping information and avoid access abnormalities.

To sum up, domain name cache is one of the core technologies to improve network access efficiency. From core concepts, operating principles to actual functions and hierarchical distribution, it builds a complete DNS resolution acceleration system. Through reasonable configuration and optimization of domain name cache, it can not only improve the user's online experience, but also ensure the stable operation of the DNS system. It is an indispensable and important part of the network technology system.