上一讲我们学习了HTTP协议使用的TCP/IP协议栈，我们知道HTTP协议是运行在TCP/IP之上的。
IP协议的职责是“互连”。它位于 MAC 层之上，使用 IP 地址将 MAC 号转换为四位数字。这样抽象了物理网卡的MAC地址，发展了很多“新玩法”。
比如分为A、B、C、D、E五种，公网地址和私网地址，子网用掩码划分。只要每个小网络在IP地址的概念上达成一致，无论在MAC层有多么不同，都可以接入TCP/IP协议栈，最终汇聚成整个互联网。
然而，越来越多的电脑接入互联网，IP地址的弊端暴露无遗。最重要的是它“对人不友好”。虽然比 MAC 的 16 进制数要好，但仍然难以记忆和输入。 .
如何解决这个问题呢？
然后“以人之道还人”，再次抽象出IP地址，将数字形式的IP地址转换成更有意义、更易记的名字，在字符串的层次上添加。 “新戏”。于是，DNS域名系统就出现了。
(Last time, we learned the TCP / IP protocol stack used by HTTP protocol. We know that HTTP protocol runs on TCP / IP.The responsibility of IP protocol is "interconnection". It is located above the MAC layer and uses IP address to convert the MAC number into four digits. This abstracts the MAC address of the physical network card and develops many "new ways to play".For example, it is divided into five types: A, B, C, D and E. public network address and private network address, and subnet is divided by mask. As long as each small network agrees on the concept of IP address, no matter how different it is in the MAC layer, it can access the TCP / IP protocol stack and finally converge into the whole Internet.However, more and more computers are connected to the Internet, and the disadvantages of IP address are exposed. The most important thing is that it is "unfriendly to people". Although it is better than the hexadecimal number of MAC, it is still difficult to remember and inputHow to solve this problem?Then "return people with the way of people", abstract the IP address again, convert the IP address in digital form into a more meaningful and memorable name, and add it at the level of string. "New play". Therefore, DNS domain name system appeared.)
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