[dns-operations] underline in TXT's host

Feng He fenghe at nsbeta.info
Fri Dec 14 08:50:48 UTC 2012

于 2012-12-14 16:44, Stephane Bortzmeyer 写道:
> 1) What is on the left side is not always a host name, far from it (if
> you have learned in a book that DNS is here to "map host names to IP
> addresses", burn the book immediately, it was written by someone who
> does not know the DNS).
> 2) Domain names can have almost any character, and it does not depend
> on the record type. If you have learned that DNS allows only LDH in
> domain names, burn the book again and read instead RFC 2181, section
> 11.

Thanks. but,

 From RFC 952
    A "name" (Net, Host, Gateway, or Domain name) is a text string up
    to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus
    sign (-), and period (.).  Note that periods are only allowed when
    they serve to delimit components of "domain style names".

    No blank or space characters are permitted as part of a
    name. No distinction is made between upper and lower case.  The first
    character must be an alpha character [Relaxed in RFC 1123] .  The last
    character must not be a minus sign or period.

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