What is DNS iteration? The principle and function of DNS iteration are explained in detail

in daily network access, domain name resolution is the core link connecting users and websites, and DNS iteration is a crucial operation mode in this link. Many users may be unfamiliar with this term, but every time they enter a URL to open a webpage, DNS iteration silently plays a role in the background. This article will dismantle the core logic of DNS iteration from the basic definition, operation principle, practical role and other dimensions, so that you can clearly understand the value of this network technology.

What is the basic definition of DNS iteration?

to understand DNS iteration, we must first start with the basic logic of domain name resolution and clarify its positioning in the entire process.

1, the core connotation of DNS iteration

DNS iteration is a query mode in the domain name system, which means that when the local DNS server receives the user's domain name resolution request, it does not directly return the final Internet Protocol Address, but gradually initiates a query to the higher-level DNS server, and each step obtains the address of the next-level server until the Internet Protocol Address of the corresponding domain name is found and then returned to the user. Unlike recursive query, the query process of DNS iteration is advanced step by step, and each step depends on the query result of the previous step.

2, applicable scenarios of DNS iteration

DNS iteration is mainly used in the interaction between DNS servers, and the local DNS server usually uses this mode to initiate queries to the root DNS server, top-level domain DNS server, etc. For ordinary users, most of the contact is the final result returned by the local DNS server, while the operation process of DNS iteration is hidden in the background to ensure the efficient advancement of domain name resolution.

What are the operating principles of DNS iteration?

grasp the operation principle of DNS iteration, can help us clearly see the complete process of domain name resolution, understand the core role of each step.

1, the initiation of the initial inquiry

when the user enters a domain name in the browser and initiates an access request, the local DNS server will first check whether there is an Internet Protocol Address corresponding to the domain name in its own cache. If there is no cache, it will start a DNS iterative query. The first step is to make a request to the root DNS server. The root DNS server does not directly return the Internet Protocol Address, but returns the address of the corresponding top-level domain DNS server, such as the server address of the .com or .cn domains.

2, the promotion process of hierarchical query

the local DNS server obtains the top-level domain DNS server address, it will initiate a second DNS iteration query to the server. The top-level domain DNS server will not return the final IP, but the authoritative DNS server address corresponding to the domain name. Then the local DNS server continues to initiate a query to the authoritative DNS server, and the authoritative DNS server will return the Internet Protocol Address corresponding to the domain name. At this point, the DNS iteration query process is completed.

3, result return and cache

the local DNS server to obtain the Internet Protocol Address, on the one hand will return the result to the user, so that the user's browser can connect to the target website; on the other hand, the corresponding relationship between the domain name and the Internet Protocol Address will be stored in the cache, when other users initiate the same domain name resolution request, you can directly return the result from the cache, without starting the complete DNS iteration process again, to improve the efficiency of resolution.

3. What is the core role of DNS iteration?

as an important mode of domain name resolution, DNS iteration plays an irreplaceable role in ensuring network access efficiency and stability.

1, reduce the load pressure of DNS servers

if all queries are in recursive mode, the superior DNS server needs to handle the user's resolution request throughout the process and bear a lot of query pressure. The DNS iteration distributes the query task to the servers of each level, and the servers of each level only need to process the query requests of the corresponding range and return the address of the next level server, which effectively reduces the load of a single server and ensures the stable operation of the entire DNS system.

2, improve the overall efficiency of domain name resolution

DNS iterative step-by-step query mode allows the local DNS server to accurately locate the authoritative server responsible for the corresponding domain name, avoiding unnecessary query paths. At the same time, the caching mechanism of the local DNS server can store the resolution results of commonly used domain names, and subsequent identical requests do not need to perform a complete DNS iteration process again, further shortening the waiting time of users.

3, enhance the fault tolerance of domain name resolution

in the DNS iterative query process, if a server at a certain level fails, the local DNS server can choose other servers at the same level to initiate the query, without interrupting the entire resolution process due to the failure of a single server. This distributed query mode greatly improves the fault tolerance of domain name resolution and ensures the continuity of user network access.

What is the difference between DNS iteration and recursive query?

a deeper understanding of the nature of DNS iteration, we need to compare it with another common query pattern, recursive query, to clarify the core difference between the two.

1, different

DNS iterative query body is the local DNS server, which needs to actively initiate queries to servers at all levels to gradually advance the process. The query body of the recursive query is the user equipment. After the user equipment initiates a request to the local DNS server, it does not need to participate in the subsequent query process, and waits for the local DNS server to return the final result.

2, differences in process complexity

DNS iterative process is relatively complex, it needs to go through multiple rounds of hierarchical queries, each step depends on the results of the previous step, and has certain requirements for the performance of the local DNS server. The recursive query process is simple for the user equipment, only one request needs to be initiated, but the requirements for the local DNS server are higher, and the whole process needs to be handled.

sum up, DNS iteration is the core operation mode in the domain name resolution process. From the basic definition to the operation principle, to the actual role, it revolves around improving the efficiency and stability of network access. It balances the load of DNS servers at all levels through the step-by-step query mode, shortens the resolution time with the help of the caching mechanism, and has strong fault tolerance. Understanding the value of DNS iteration can help us understand the underlying logic of network access more clearly and improve the level of awareness of network technology.