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From: Barry Margolin <[EMAIL PROTECTED]>
Newsgroups: comp.protocols.tcp-ip.domains
Subject: Re: NSI may revoke 100's of domains
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Date: Fri, 14 Jan 2000 15:18:08 GMT
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In article <85mrdk$jj9$[EMAIL PROTECTED]>,
Rahul Dhesi <[EMAIL PROTECTED]> wrote:
>Host names are, but host aliases, defined via CNAME records, are not.
>In support my this I hereby quote yet another RFC, this time the "best
>current practice" RFC 2317:
>
> $ORIGIN 2.0.192.in-addr.arpa.
> 129 CNAME 129.128/26
An alias that doesn't point to an A record isn't a "host alias".
> Some DNS implementations are not kind to special characters in domain
> names, e.g. the "/" used in the above examples. As [3] makes clear,
> these are legal, though some might feel unsightly. BECAUSE THESE ARE
> NOT HOST NAMES THE RESTRICTION OF [2] DOES NOT APPLY. Modern clients
> and servers have an option to act in the LIBERAL AND CORRECT FASHION.
There was a bug in a version of BIND, when they were first adding the
syntax checking. It was fixed in the next point release. The BIND
developers didn't intentionally mean to restrict CNAMEs, they just messed
up.
>I have added emphases in three places. The use of '/' in aliases
>defined by CNAME records is 'correct'. A host alias defined by a CNAME
>record is not a host name and not constrained by restrictions imposed on
Hostnames are defined by their use. Something that appears after the @ in
an email address, the hostname part of a URL, or the parameter to a telnet
command, for example, is a hostname. Something that's used as the
parameter to a reverse lookup is an IP address, and the result is a
hostname.
In some cases you know that the only appropriate use of something in DNS is
as a hostname: the name of an A or MX record, or the target of a PTR
record. In those cases, it's reasonable for the name server to perform a
sanity check. If you don't want it, you can turn it off with the
"check-names" option.
>host names. The same RFC also advises, of course, that we use a hyphen
>instead, because not all software will properly handle slashes. But not
>because any RFC requires it.
Right, that's the "be conservative in what you send" part of The
Interoperability Principle. If you can anticipate someone else messing up,
don't go out of your way to tickle that bug.
--
Barry Margolin, [EMAIL PROTECTED]
GTE Internetworking, Powered by BBN, Burlington, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
