Re: [Softwires] 4rd Address Mapping - version-01

Hi Qiong,

Some fields of a unified address format for double translation and encapsulation might be unnecessary for hub and spoke, but using the same format should be advantageous for maintenance and training if for nothing else (assuming that any added complexity is negligible enough).

Believing that a completely unified format is possible, I mentioned it to Alain.
Also, I volunteered to be editor-coordinator for this to happen, but decision of who does what is his.

Regards,
RD

Le 4 oct. 2011 à 00:13, Qiong a écrit :

> Hi Remi and Wojciech,
> 
> Thanks for your clarification. I fully agree with you that embedding the full IPv4 address in the last 64 bits would be quite helpful for some kind of source address classification and I also suggest that this can be taken in the same way for encapsulation-based approach. It would be easier for systems in-the-middle to identify the IPv4 address without packet decapsulation. 
> 
> I guess the thing that Ole has mentioned to "look at 24 bits in the middle of IPv6 address" is for CE to determine whether a downstream IPv6 packet should be taken for translation or native forwarding. Here, for a dual-stack host, there would be no difference in the first /64 bits for a native IPv6 packet and a translated packet. What's why the CE should further looking into the last 64 bits to determine the translation process or native forwarding. Maybe Ole can clarify for this part again.
> 
> However, the situation would still be different in "Hub & Spoke" and "Mesh" mode. For Hub & Spoke case, since BR will have a default prefix/address, it would be easily to identify the translated traffic from native IPv6 traffic by just doing source address routing lookup for a downstream packet. So, the corresponding mechanics would be different.
> 
> Thanks 
> 
> Best wishes
> 
> Qiong
> 
> 2011/10/3 Wojciech Dec <wdec@cisco.com>
> 
> 
> 
> On 02/10/2011 02:58, "Qiong" <bingxuere@gmail.com> wrote:
> 
> Hi Ole and Remi,
> 
> > This is my answer to your first (double) question.
> > If it is not enough, as suggested below, please explain what you don't understand.
> 
> I specifically do not want a solution that changes forwarding behaviour for _all_ IPv6 packets.
> e.g. looking at 24 bits in the middle of an IPv6 address is such a change.
> 
> Woj> What are you referring to? Routing “just works” as normal and is non disaggregated because of the CE-index in the prefix. Classification can/is done on a subset of the v6 address, and that is perfectly legit.
> 
> 
> I don't understand what requirements you are basing this 'solution' on.
> if the 4rd / dIVI CE takes (a well known or provisioned) /64 prefix out of the delegated prefix. then why do you need any of that?
>  
> Qiong : I agree that routing lookup for a provisioned /64 prefix would be better that extracting certain bits for each IPv6 address in CE. This would bring less change to existing routing model.
> 
> Woj> There is no change to the existing destination based routing model. Each CE is uniquely addressed by the CE bits in the top /64 – ie the CE index is as proposed by all the 4rd and divi-pd drafts. The full v4 source address of each CE is however also embedded in the interface-id, as per RFC6052. There appears to be no cost for this operation, and has the upside of the full v4 info visible in the header and allowing source based classification (should one want to do that). 
> 
> Regards,
> Woj.
> 
> Best wishes
> 
> Qiong 
> 
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