TCP/IP详解 卷1 1.5

1.5 The Domain Name System

域名系统

Although the network interfaces on a host, and therefore the host itself, are known by IP addresses, humans work best using the name of a host. In the TCP/IP world the Domain Name System (DNS) is a distributed database that provides the mapping between IP addresses and hostnames. Chapter 14 looks into the DNS in detail.

虽然主机的网络接口以及主机本身可通过 IP 地址查询，但是人们还是希望通过名字寻找主机。在 TCP/IP 中， DNS 是提供 IP 和主机名映射的分布数据库。

For now we must be aware that any application can call a standard library function to look up the IP address (or addresses) corresponding to a given hostname. Similarly a function is provided to do the reverse lookup― given an IP address, look up the corresponding hostname.

如今我们需要意识到，任何程序均可调用标准库函数，查找主机名对应的 IP 地址。相类似的功能是反向查找――给出 IP 地址，查找相应的主机名。

Most applications that take a hostname as an argument also take an IP address. When we use the Telnet client in Chapter 4, for example, one time we specify a hostname and another time we specify an IP address.

许多引用主机名做参数的程序同样也引用 IP 地址。例如第 4 章中使用 Telnet 客户端，即可用用户名也可用 IP 地址。