On 2012/02/07, at 16:46, Rémi Després wrote:

--snip--

>>> 
>>>>>> I think that operators who already deploy such dual-stack network is 
>>>>>> supposed that they have address mapping table,
>>>>> 
>>>>> I would rather suppose that ISPs that have added IPv6-prefix delegation, 
>>>>> say /56s, to an existing IPv4 network did it without mixing their IPv6 
>>>>> plan with their IPv4 prefixes.
>>>>> I am ready, however, to look seriously at individual cases where choices 
>>>>> were different.
>>>> 
>>>> Basically provision MAP CE is based on its delegated IPv6 prefix in 
>>>> concept. It is opposed to your case but technically possible.
>>> 
>>> 
>>>> Now I concern that it requires much complicated CE implementation.
>>> 
>>> All what is required is that CEs set an address bit if hub&spoke topology 
>>> is required.
>>> 
>> 
>> So how CE decide to set the bit, and when the CE figure it out?
> 
> The CE knows it must set this bit if, and only if, it received at 
> initialization a Topology-variant parameter set to Hub&spoke (sec 4.1).
> In this case, the CE sets bit 79 to 1 in IPv6 destination addresses of all 
> packets it sends.
> 
> BTW, this bit should better, for clarity, be given a name, e.g. bit B meaning 
> To-BR bit (or whatever better idea one could propose). I plan to do it in the 
> next version.
> 

So you mean that if the hub&spoke bit is set, a CE derives /112 IPv6 prefix as 
4rd end point from IPv4 address which is already assigned. Otherwise, a CE 
derives its IPv4 address from delegated IPv6 prefix. right?

cheers,
--satoru
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