Re: [Softwires] Moving forward with 4rd-T, 4rd-E & 4rd-U

Rémi Després <despres.remi@laposte.net> Sat, 04 February 2012 10:23 UTC

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To: Tina TSOU <Tina.Tsou.Zouting@huawei.com>
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Cc: Softwires WG <softwires@ietf.org>, Yong Cui <cuiyong@tsinghua.edu.cn>, Ralph Droms <rdroms@cisco.com>
Subject: Re: [Softwires] Moving forward with 4rd-T, 4rd-E & 4rd-U
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Le 2012-02-04 à 10:48, Tina TSOU a écrit :
> Sent from my iPad
> On Feb 3, 2012, at 11:40 PM, "Rémi Després" <despres.remi@laposte.net> wrote:
>> Le 2012-02-03 à 18:45, Ole Trøan a écrit :
...
>>> I know we've discussed the V octet a lot earlier. I can't remember all the nuances we discussed. could you summarize, e.g. in the feature draft I suggested earlier.
>> ...
>> "The V octet is a 4rd-specific mark. Its function is to ensure that 4rd does not interfere with the choice of subnet prefixes in CE sites.  It can also facilitate maintenance by facilitating distinction between 4rd Tunnel packets and native-IPv6 packets.  Within CEs, IPv6 packets can safely be routed to the 4rd function based on a /80 prefix because no internal route for native IPv6 can have a destination prefix that start with this one." 

> Assume there is a CE Router with /32 IPv6 addresses in an enterprise network.
> "based on a /80 prefix" for what? Would u elaborate or reword the last sentence for better understanding for readers like me? Merci.

 If a CE has a /32 prefix, say p:p::/32, and some Mapping rule that derives an IPv4 prefix or address from it, all 4rd Tunnel packets sent to it have, according to the 4rd-U draft, an IPv6 destination starting with p:p:0:0:3000::/80.
 Within the CE, all packets whose destination start with this prefix can be routed, within the CE, to the 4rd function. 
 Native IPv6 packets are routed in the CE with prefixes that are either longer than the CE 4rd prefix and non-overlapping, or shorter. In both cases adding a route for the 4rd /80 doesn't impact how they are routed.
 Does this clarify?

Regards,
RD