Subject: Re: An argument why bname-style delegation is needed (was: [dnsext] DNSEXT charter and treating DNS names as "the same")

From: "zhanglikun" <[email-masked]>
Date: Thu, 12 Aug 2010 20:59:13 +0800

[ Moderators note: Post was moderated, either because it was posted by
   a non-subscriber, or because it was over 20K.  
   With the massive amount of spam, it is easy to miss and therefore 
   delete relevant posts by non-subscribers. 
   Please fix your subscription addresses. ]

I don't plan to add more arguments for the provision way, since the
complexity it brings when comes to multiple-labels domain equivalence, which
has been mentioned by former emails, it's o(a^n),  instead xName is o(n) .

Now let me go back to c+dname VS bname.

If one zone has records:
a.net.  cname  a.cn.
a.net.  dname  b.com.

user do the query with the following sequence:
dig  a.net.  cname
dig  a.net.  dname

if the cache isn't aware of the new c+dname rules, will the second query
will chase down to b.com.? it will try to chase down a dname record
belonging to a.cn. rather than b.com.  Except the c+dname has one rule: the
rdata part of should be same.

anther, when doing update, you have to be very careful to decide whether to
remove/add c+dname or just one of them.
Last, c+dname will double zone size, compared with bname.

My point is +1 for bname.

Anyway, this topic recall me to the added voice saying no to DNAME long
before(five years ago or more), somebody said he had a complete dislike for
the DNAME, not just the document but also the idea, even though the DNAME
had born.  :)

Thanks
Likun Zhang