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Re: [Softwires] Path to move forward with 4rdŠ

Rémi Després <despres.remi@laposte.net> Fri, 23 March 2012 17:14 UTC

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From: Rémi Després <despres.remi@laposte.net>
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Date: Fri, 23 Mar 2012 18:13:33 +0100
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To: Guanghui Yu <yu.guanghui@gmail.com>
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Subject: Re: [Softwires] Path to move forward with 4rdŠ
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Hi, Guanghui,

Le 2012-03-23 à 04:04, Guanghui Yu a écrit :

> Hi Yiu
> 
>    4rd-u changes the IPv6 header architecture (redefine fragmentation header extension)

4rd-U uses between CEs and BRs an IPv6 packet format that not only is completely authorized, but that is already 
used in double translation: RFC6145 also adds a fragmentation header to some unfragmented packets (sec 4.).


> and IPv6 address architecture (different meaning of u-bit when g-bit=1).

- U builds on the fact that all IPv6 unicast addresses are so far either universal scope (u=1 g=0) or local link scope (u=0 g=any value). This (fortunately) leaves an escape combination for new types of addresses (U is only one of these possible addresses, but the first one).
- A 4rd-U address happens to be partially universal scope (embedded public IPv4 addresses) and partially ISP-domain scope (dependent on ISP defined mapping rules). None of the existing formats is therefore mandatorily applicable.
- Impact on IPv6 address architecture is only a backward compatible extension: no interference is possible with anything that works in conformance with current IPv6 specifications.


> These are the fundamental changes. If 4rd-u becomes the standard, then there will be new defined “IPv6” packets on the Internet, which are not compatible with existing IPv6 packets and

Please see above.

> no existing devices can understand those packets.

Only BRs and CEs need to understand that these packets have IPv4 compatible payloads.


Regards,
RD

>    
> 
> Yu Guanghui <ygh at dlut.edu.cn>
> Network and Information Center
> Dalian University of Technology, China
> 
> 
> On Fri, Mar 23, 2012 at 10:10 AM, Lee, Yiu <Yiu_Lee@cable.comcast.com> wrote:
> Hi Guanghui,
> 
> I agree that both MAP and 4rd-u are similar technology and solving the same problem. From technical perspective, can you elaborate this a lithe bit? 
> 
> Thanks,
> Yiu
> 
> From: Guanghui Yu <yu.guanghui@gmail.com>
> Date: Thu, 22 Mar 2012 20:26:40 +0800
> To: Softwires WG <softwires@ietf.org>
> Subject: Re: [Softwires] Path to move forward with 4rd…
> 
> I read 4rd-u draft and found it is flawed.
> 
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> Softwires mailing list
> Softwires@ietf.org
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