Re: [Softwires] MAP&4rd-U - DS routing replaced by v6-only routing in hub&spoke topology

Satoru Matsushima <> Tue, 07 February 2012 16:35 UTC

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From: Satoru Matsushima <>
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Date: Tue, 7 Feb 2012 17:35:25 +0100
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Cc: Softwires WG <>, Wojciech Dec <>
Subject: Re: [Softwires] MAP&4rd-U - DS routing replaced by v6-only routing in hub&spoke topology
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On 2012/02/07, at 16:46, Rémi Després wrote:


>>>>>> 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?