"to." 域名是什么，为什么 "http://to." 有效？
What is the "to." domain name, and why does "http://to." work?
在查看最短域名列表时，我发现了域名 to./。
如果我转到 http://to./，我会看到默认的 Apache "It works!" 页面。
那么，这个域名是如何运作的呢？它怎么只有顶级域名，没有名字？
"to" 是汤加国家的 Top-Level Domain (TLD)，就像 "uk" 是英国一样。
尾随点有效 - 实际上是 the canonical correct or "absolute" form.
It's a little-known fact, but fully-qualified (unambiguous) DNS domain names have a dot at the end.
People running DNS servers usually know this (if you miss the trailing dots out, your DNS configuration is unlikely to work) but the general public usually doesn't. A domain name that doesn't have a dot at the end is not fully-qualified and is potentially ambiguous. This was documented in the DNS specification, RFC 1034, way back in 1987:
来自RFC 1034：
Since a complete domain name ends with the root label, this leads to a
printed form which ends in a dot. We use this property to distinguish between:
a character string which represents a complete domain name
(often called "absolute"). For example, "poneria.ISI.EDU."
a character string that represents the starting labels of a
domain name which is incomplete, and should be completed by
local software using knowledge of the local domain (often
called "relative"). For example, "poneria" used in the
ISI.EDU domain.
因此 'to.' 是 'to' TLD 的绝对域名。域名仅用于解析 (IP) 地址，如果解析，则可以非常愉快地指向 Web 服务器。
大多数 TLD 无法解析为地址 - 但对此没有技术限制。
在查看最短域名列表时，我发现了域名 to./。
如果我转到 http://to./，我会看到默认的 Apache "It works!" 页面。
那么，这个域名是如何运作的呢？它怎么只有顶级域名，没有名字？
"to" 是汤加国家的 Top-Level Domain (TLD)，就像 "uk" 是英国一样。
尾随点有效 - 实际上是 the canonical correct or "absolute" form.
It's a little-known fact, but fully-qualified (unambiguous) DNS domain names have a dot at the end.
People running DNS servers usually know this (if you miss the trailing dots out, your DNS configuration is unlikely to work) but the general public usually doesn't. A domain name that doesn't have a dot at the end is not fully-qualified and is potentially ambiguous. This was documented in the DNS specification, RFC 1034, way back in 1987:
来自RFC 1034：
Since a complete domain name ends with the root label, this leads to a printed form which ends in a dot. We use this property to distinguish between:
a character string which represents a complete domain name (often called "absolute"). For example, "poneria.ISI.EDU."
a character string that represents the starting labels of a domain name which is incomplete, and should be completed by local software using knowledge of the local domain (often called "relative"). For example, "poneria" used in the ISI.EDU domain.
因此 'to.' 是 'to' TLD 的绝对域名。域名仅用于解析 (IP) 地址，如果解析，则可以非常愉快地指向 Web 服务器。
大多数 TLD 无法解析为地址 - 但对此没有技术限制。