Re: Operational experience with 3 degrees

[JINMEI Tatuya / $B?@L@C#:H(B <jinmei@isl.rdc.toshiba.co.jp>]

>>>>> On Wed, 26 Mar 2003 19:59:33 +0100, 
>>>>> "Jeroen Massar" <jeroen@unfix.org> said:

>> >> - some ignore AAAA queries (causing a delay to fallback).
>> >> you can see this when you try to resolve AAAA for "ftp.mozilla.org"
>> >> at 64.12.182.70 (gdns-02-ftp-dom.ns.aol.com)

(snip)

>> If you try to resolve an RR for ftp.mozilla.org, you'll follow a CNAME
>> chain and will eventually see the name is in fact an alias for
>> ftp-mozilla.gftp-mozilla.netscape.com.

> <SNIP>

>> From RFC2181:
> 8<-----------------------------
> 10.1. CNAME resource records

>    The DNS CNAME ("canonical name") record exists to provide the
>    canonical name associated with an alias name.  There may be only one
>    such canonical name for any one alias. 
-----------------------------> 8

> I interpret this as "CNAME chains are not allowed" thus the above
> system should not work at all... apparently in some cases it works
> though.

First of all, "CNAME chains" are not the essential part of this
problem.  The point is that we cannot resolve a non-A RR for
gftp-mozilla.netscape.com zone at 64.12.182.70, to which CNAMEs are
not related at all.

Secondly, Section 10.1 of RFC 2181 talks about so-called "multiple
CNAMEs", which is a different notion from what I called "a CNAME
chain".  Multiple CNAMEs are multiple different CNAMEs for a single
domain name in a single zone, like:

www.jinmei.org. IN CNAME www1.jinmei.org.
www.jinmei.org. IN CNAME www2.jinmei.org.

While I used the word a "CNAME chain" like this:

foo.jinmei.org. IN CNAME bar.jinmei.org.
bar.jinmei.org. IN CNAME baz.jinmei.org.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					jinmei@isl.rdc.toshiba.co.jp