Learn about DNS series (i) Basics, overview

This series focuses on the knowledge of DNS servers under Windows, because DNS and ad are tightly coupled, so ad-related DNS applications and knowledge will be described in the ad column.

This is the first section of this series.

I think no one will directly enter the IP address in the interview, instead of a simple, easy to remember characters, there are numbers, such as www.163.com; there are also pure letters, such as www.qq.com, as long as the network connection is no problem, you can directly access the corresponding Web site. But in theory access to the URL still need to use the IP address, but the character conversion to IP address this part of the work by the DNS server, and this conversion process for the client is completely transparent.

Before telling about DNS, let's take a look at several concepts related to domain names.

What is a domain name?

The domain name, namely DomainName, is to say it is by the English letter, the Arabic numeral as well as horizontal "-" a string of characters, and English is not case-sensitive, usually a domain name can be divided into the main body and the suffix 2 parts, each part by a small point. Separated. For the common 163.com example, 163 is the subject of this domain name, and the following. com indicates that the domain name belongs to the international domain name, as well as. NET,. cn, and so on. These two parts constitute a complete domain name. A friend may ask, then we common www.163.com is what. Overall, this is a URL address, not a domain name. In terms of refinement, www is a host name, running on this host Web server, when the client input www.163.com, the system will query the IP address of this address on a system, if all normal will soon return the IP address of this host, The browser then initiates HTTP requests to this address for Web page parsing. The "one system" mentioned in this process is the DNS system that we are talking about.

What is DNS?

Usually, we locate a public network computer mainly depends on the IP address, if this computer is providing Web browsing services, IP 1.1.1.1. Access can be directly entered the IP address, because this address is easy to remember, but the computer on the network thousands, IP address is a series of disorderly numbers, the human brain to memorize these figures, it is obviously unrealistic, so the need for a way or method to rescue us from the digital abyss, after continuous exploration, People have finally found a good solution, that is, by combining some of the rules and pieces of characters, so that they can express a certain meaning, and then the name of the server with the IP address, we can make these combinations into domain names. Of course, the definition of domain name is far more rigorous and normative than here. Who is going to implement this part of the work or function, which leads us to the protagonist of this series: DNS. In today's view, the normal operation of the DNS system is directly related to the security and stability of the entire Internet system.

DNS is the domain name resolution system. As mentioned earlier, it can convert a domain name to an IP address, or vice versa. Of course, this is one of the most basic functions of DNS.

When it comes to DNS, we can't help but talk about the domain name, the concept can refer to the above section, then how the two are combined together? Let's take a look at the overall structure of the Internet domain name.

The domain name occupies an extremely important position throughout the Internet network because it has a rigorous pyramid-like hierarchy pattern, often called a namespace. When we read DNS related information, we often encounter the word "namespace". Then how to understand it. Take a look at the picture below to help you better understand the concept of namespaces.