Re: [BEHAVE] two ideas - draft-wing-behave-dns64-config-02

"Dan Wing" <dwing@cisco.com> Mon, 01 March 2010 19:57 UTC

From: Dan Wing <dwing@cisco.com>
To: 'Dacheng Zhang' <zhangdacheng@huawei.com>, behave@ietf.org
References: <019001cab785$62d06b80$070d6f0a@china.huawei.com>
Date: Mon, 01 Mar 2010 11:57:54 -0800
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Subject: Re: [BEHAVE] two ideas - draft-wing-behave-dns64-config-02
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> -----Original Message-----
> From: behave-bounces@ietf.org 
> [mailto:behave-bounces@ietf.org] On Behalf Of Dacheng Zhang
> Sent: Saturday, February 27, 2010 12:18 AM
> To: behave@ietf.org
> Subject: [BEHAVE] two ideas
> 
> Hello, everybody:
> 
>  
> 
> After reading draft-wing-behave-dns64-config-02, I have two 
> ideas here, and hope to get your kindly comments:
> 
>  
> 
> 1. In section 3.2, it is suggested to use DNSsec to disable 
> DNS64. But in order to deal with the circumstance where 
> synthesized addresses have been already encapsulated in AAAA 
> records, 

I don't understand what is meant by "have been already 
encapsulated"; DNS64 does the synthesis on-the-fly, so they
are not "already" synthesized AAAA responses.  Could you clarify?

> maybe it is a good idea to specify a new flag in the 
> DNS answer containing an AAAA RR. The flag indicates that a 
> synthesized address is contained in the RR. An updated 
> dual-stack host can recognize it while conventional ones will 
> just ignore the flag.

I vaguely recall there was a proposal to do that, but I can't
remember the name of the I-D or the section of some other
I-D.  I can certainly add that to draft-wing-behave-dns64-config,
and I believe it would have positives and negatives nearly
identical to Section 3.2, namely:

Advantages:
  * It is simple

Disadvantages:
  * It requires dual-stack host to understand the new flag if
    if it wants to avoid using the NAT64
  
Are there other advantages or disadvantages? 

I'm not sure of the implications of the host transitioning
from dual-stack to IPv6-only.  Thoughts on that?

> 2. In the sections 3.5 and 3.6, solutions of using DHCP to 
> identify dual stack host are introduced. I want to know 
> whether it is another feasible solution to define an option 
> for dual stack hosts. If such an option is attached in a 
> request from a host, the DHCP server will ensure that the 
> host has a dual-stack. 

It seems reasonable for the DHCP Request to indicate "I am 
dual-stack".  

Advantages:
  * Simple

Disadvantages:
  * It requires dual-stack host to include this new DHCP
    option if it wants to avoid using the NAT64

How would a host transition from dual-stack to IPv6-only in
that case?  It seems that if it releases its IPv4 address,
and becomes IPv6-only, it would need to re-DISCOVER, and
indicate "I am not dual stack" (or perhaps not send the
option?).

-d


> 
>  
> 
> What do you think of them?
> 
>  
> 
> BR ^_^
> 
>  
> 
> Dacheng
> 
>

[BEHAVE] two ideas Dacheng Zhang
Re: [BEHAVE] two ideas mohamed.boucadair
Re: [BEHAVE] two ideas - draft-wing-behave-dns64-… Dan Wing