在主机名中使用下划线 [英] The use of the underscore in host names

问题描述

维基百科声明强调了由Android和Microsoft Windows系统以主机名使用。我的问题是，这些主机名是什么？你有这些奇怪的主机名的例子和它们用于什么？

解决方案

什么是主机名字？

类似于学校的课室，每个学生都有一个卷号/身份证，以便他/她被识别互联网的空间（或任何计算机网络），网络中的每个设备都需要被唯一标识。这是通过主机名完成的。因此，主机名是帮助识别网络中的设备的名称。

带有下划线（_）字符的主机名。 / p>

在有效无效的主机名的标准期间，公用终端界面是键盘的电传（TTY）ASR-33。现在这个keyborad从来没有一个下划线（_）的键（请查看此图片 http ：//www.pdp8.net/asr33/pics/kbd_top.shtml？large ），因此不可能有一个主机名带下划线（ _） 在里面。检查此链接了解更多详细信息： http://www.quora.com/Domain-Name-System-DNS/Why-are-underscores-not-allowed-in-DNS-host-names

域名中可以使用下划线（_）字符。正如这篇文章所述，可以（域名）子域名有下划线_在其中？具有下划线是完全有效的。一些示例（如帖子中所示）是 _jabber._tcp.gmail.com 或 _sip._udp.apnic.net 。另一个使用下划线的例子见 http：// ideaharbor。组织/票据/技术/启用，聊天外，谷歌 - 应用。虽然它有效地使用下划线，但不是推荐的做法。

您的帖子中的维基百科链接指出，Microsoft Windows和Android智能手机不会强制执行不使用下划线的规则主机名。不执行此规则可能会导致问题，因为许多系统拒绝这种主机名。

希望你从这个解释中得到一些东西。

编辑

在进一步调查问题上，帖子，我想说明主题名称中使用下划线：

http://networkadminkb.com/KB/a156/windows-2003-dns-and-the-underscore.aspx

Wikipedia states that underscores are used by both Android and Microsoft Windows Systems in hostnames. My question is, what are these host names? Do you have examples of these strange hostnames names and what they are used for?

解决方案

What are host names?

Analogous to a school class room where each student has a roll number/id so that he/she is identified, in the class room of Internet (or for that matter any computer network) each device that are in the network needs to be uniquely identified. This is done via a Host Name. Thus hostnames are names that helps in identifying devices in a network.

Hostnames with underscore(_) character.

During the period when the standards were being laid for the valid and invalid hostnames, the common terminal interface was the keyboard of the Teletype (TTY) ASR-33. Now this keyborad never had a underscore(_) key in it (check this pic http://www.pdp8.net/asr33/pics/kbd_top.shtml?large) and hence it was not possible to have a hostname with an underscore(_) in it. Check this link for more details: http://www.quora.com/Domain-Name-System-DNS/Why-are-underscores-not-allowed-in-DNS-host-names

Underscore(_) character can be used in the domain names. As this post states Can (domain name) subdomains have an underscore "_" in it? it is completely valid to have an underscore. Some examples(as shown in the post) are _jabber._tcp.gmail.com or _sip._udp.apnic.net. Another example of usage of an underscore is seen here http://ideaharbor.org/notes/technical/enabling-chat-outside-google-apps. Though its valid to use underscores it not a recommended practice.

The wikipedia link in your post states that Microsoft Windows and Android smartphones does not enforce the rule against using an underscore in hostnames. Non enforcement of this rule may result in problems because many systems reject such kind of hostnames.

Hope you get something out of this explanation.

EDIT

On further investigation on the issue, I came upon this wonderful post which I suppose clarifies the usage of underscore in hostnames:

http://networkadminkb.com/KB/a156/windows-2003-dns-and-the-underscore.aspx

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