Question

How do your browser and other web clients know where to find these resources? Well, every device connected to the internet has a unique Internet Protocol (IP) address that other devices can use to find it. However, IP addresses are made up of numbers and letters that are hard for humans to remember. For example, the older format of IP addresses, IPv4, looks like this: 123.45.67.89. The new version, IPv6, looks even more complicated: 2001:db8::ff00:42:8329.

您的浏览器和其他网络客户端如何知道在哪里找到这些资源呢？每个连接到互联网的设备都有一个唯一的 IP 地址，其他设备可以使用它来查找它。然而，IP 地址由数字和字母组成，对人类来说很难记忆。例如，旧版 IP 地址 IPv4 看起来像这样：123.45.67.89。新版 IPv6 更复杂：2001：db8：：ff00：42：8329。

This is where the Domain Name System (DNS) comes in. A DNS server functions as the phone book for the internet, translating domain names into IP addresses ( Figure 3-2 ). When you enter a domain name in your browser, a DNS server must first convert the domain name into an IP address. Our browser asks the DNS server, “Which IP address is this domain located at?”

这就是域名系统（DNS）发挥作用的地方。DNS 服务器像互联网上的电话簿一样运作，将域名翻译成 IP 地址（图 3-2）。当您在浏览器中输入域名时，DNS 服务器必须先将其转换成 IP 地址。我们的浏览器会向 DNS 服务器询问：“这个域名位于哪个 IP 地址？”

Figure 3-2 : A DNS server will translate a domain name to an IP address.

图 3-2：DNS 服务器将把域名翻译成 IP 地址。