Now is the Internet era, and the application of the network has penetrated into everyone’s daily life. People can quickly access various shopping, video websites, and game applications through computers or smartphones. To access a website or application, it is necessary to download the packet content from the IP address of the target server to the local device. However, in daily life, people only enter a domain name in the browser or open the APP application during the online process, and no IP address is entered during the process. Why is this?
In fact, there is a name in the middle that silently provides services but is not well known to everyone. It is the domain name resolution system, also known as the DNS resolution system, which completes the entire scheduling process of converting domain names into corresponding server IP addresses for query requests. The DNS resolution system plays a role as a guide in the entire Internet application process, accurately finding the address of the target server in the vast world of the Internet based on the user’s operation in the browser address bar or APP application, and building a virtual communication bridge between the user’s access device and the target server.
According to an article, DNS parsing is similar to subtitle groups in movies. For audiences who do not understand the language, they cannot understand the dialogue in the movie and play the role of translator. After translation, all unfamiliar languages become familiar characters. The foreign language before translation is equivalent to the domain name, and the translated text is the IP address.
Globally, hundreds of millions of domain names have been built into websites. The emergence of smartphones has made network applications more convenient and convenient, and the entire access process is inseparable from DNS resolution systems. So perhaps some people will ask, how did such a huge job come about? In fact, the process of parsing is also divided into many steps, through layer by layer decomposition, to achieve a one-to-one correspondence between domain names and IP addresses.
The DNS resolution process is initiated by the DNS service module of the local device and then routed to the network operator DNS (Local DNS) for query. If there are cache records saved after previous queries by other users in the operator’s DNS cache, the IP address of the domain name requested by the local device can be immediately returned. However, due to everyone’s different hobbies and habits, there is no record of the current request to access the domain name in the operator’s DNS cache. At this time, the operator’s DNS server will initiate layer by layer query requests to the superior DNS server, with different responsibilities assigned to each level:
13 top-level DNS servers (root servers) worldwide: store the IP addresses of domain name servers with all suffixes, and query the corresponding domain name server IP based on the domain name suffix
Domain Name Server: Stores the registration information and NS server addresses of all domain names. Find the IP address of the DNS resolution server (authoritative DNS) that provides domain name resolution services based on the NS address recorded in the domain name registration information
Authoritative DNS: Stores all domain name resolution records that provide resolution services, and can directly query the resolution record values added to access the domain name
Operator DNS: Initiate a query request to the superior DNS resolution server based on the user’s resolution access request, and then point the final queried domain name resolution record to the address to inform the requesting device.
Theoretically, every time you use a computer browser or operate an APP application, you need to send a domain name resolution query request to DNS, which requires the entire DNS resolution system to respond to the query. Based on the final results, you can obtain web content or game data, video images, beautiful music, and so on from the target server.
As an intermediary station directly facing users to access devices, operator DNS receives various domain name resolution query requests all the time in daily life. Many times, there will be multiple consecutive individuals submitting resolution query requests to the same domain name. For example, during the Taobao Double 11 event, everyone will focus on requesting access to Taobao’s website. If you follow the process of the DNS resolution system every time to search all DNS servers to obtain the final resolution result, the time it takes will be long and meaningless. To reduce this avoidable operation, DNS operators store the domain name results obtained from each superior query into the DNS server, so that the next time there is a request for the same domain name resolution query, they can call this result to respond and answer, which is also known as DNS caching.
In summary, the prosperity and convenience of our current Internet cannot be separated from the DNS resolution service.
