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This article introduces the relevant knowledge of "how to understand DNS domain name resolution". In the operation process of actual cases, many people will encounter such difficulties. Next, let Xiaobian lead you to learn how to deal with these situations. I hope you can read carefully and learn something!

DNS(Domain Name System) is a naming system used on the Internet to translate user-friendly machine names into IP addresses. The domain name system is actually the name system. Why not "name" instead of "domain"? This is because many "domains" are used in this Internet naming system, and hence the term "domain name" appears. "Domain name system" clearly indicates that this system is applied to the Internet.

Domain Name System DNS

As we all know, IP addresses consist of 32 binary digits. When communicating with a host on the Internet, users are obviously reluctant to use the hard-to-remember 32-bit binary host address. Even dotted-decimal IP addresses are not easy to remember. Instead, people prefer to use host names that are easier to remember. However, the machine does not use domain names but IP addresses when processing IP datagrams. This is because the IP address length is fixed, and the length of the domain name is not fixed, and the machine is more difficult to process.

The resolution of domain names to IP addresses is done by a number of domain name server programs distributed across the Internet. Domain name server programs run on dedicated nodes, and the machines running domain name server programs are often referred to as domain name servers.

DNS Structure of Internet Domain Names

Due to the large number of Internet users, the Internet is named using a hierarchical tree structure naming method. Any host or router connected to the Internet has a unique hierarchical name, the domain name. Here, a domain is a manageable partition of a namespace.

DNS stipulates that the labels in domain names are composed of English and numbers, each label does not exceed 63 characters (for memory convenience, generally no more than 12 characters), and does not distinguish between upper and lower case letters. No punctuation except hyphen (-) can be used in labels. The lowest-level domain name is written on the far left, while the highest-level character is written on the far right. A complete domain name consisting of multiple labels does not exceed a total of 255 characters. DNS does not specify how many subordinate domain names a domain name must contain, nor does it specify what each subordinate domain name means. Each level of domain name is managed by the domain name authority immediately above it, while the top-level domain name is managed by ICANN. In this way, each domain name can be unique throughout the Internet, and it is easy to design a mechanism to find domain names.

Domain names are logical concepts and do not represent the physical location of the computer. According to December 2006 statistics, there are now 265 top-level domains (TLD), divided into three categories:

(1)National top-level domain nTLD: ISO3166 applies. cn stands for China, us stands for America, uk stands for Britain, and so on. Country domain names are often referred to as ccTLDs (cc stands for country code contry-code).

(2)gTLD: The most common gTLD are: com(corporate enterprise), net(network service organization), org(non-profit organization), int(international organization), gov(US government department), mil(US military department).

(3)Infrastructure domain name (infrastructuredomain): There is only one such top-level domain name, arpa, which is used for reverse domain name resolution, so it is called reverse domain name.

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