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From: =?iso-8859-1?Q?R=E9mi_Despr=E9s?= <despres.remi@laposte.net>
In-Reply-To: <80C2DFB3-0E21-44F2-9FCA-F0B4CF88DA22@gmail.com>
Date: Tue, 7 Feb 2012 14:03:18 +0100
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 <80C2DFB3-0E21-44F2-9FCA-F0B4CF88DA22@gmail.com>
To: Satoru Matsushima <satoru.matsushima@gmail.com>
Cc: Softwires WG <softwires@ietf.org>, Wojciech Dec <wdec@cisco.com>
Subject: Re: [Softwires] MAP&4rd-U - DS routing replaced by v6-only routing in
 hub&spoke topology
Precedence: list

Le 2012-02-07 =E0 13:07, Satoru Matsushima a =E9crit :

> Hi Remi-san,
>=20
> On 2012/02/07, at 11:13, R=E9mi Despr=E9s wrote:
>=20
>> Hello Ole, Tetsuya-san, Wojciech,
>>=20
>> In a use case described in the 4rd-U draft (sec 5.3), an ISP replaces =
its dual-stack routing by IPv6-only routing.
>> For this, independently from the number of IPv4 prefixes it has to =
support, it uses only one mapping rule.
>> (By replacing each IPv4 route by an equivalent IPv6 route, it ensures =
that all customers keep their IPv4 addresses.)
>>=20
>=20
> I don't think that it could work as you explained in that section. For =
example, the BR would need to check a received packet from a CE whether =
it has correct source address in mapping rule or not. It means that the =
BR must know all address mappings for CE between IPv4 addresses and IPv6 =
prefixes. Is it correct understanding?

Ingress filtering of the domain has checked that the IPv6 source starts =
with the delegated IPv6 prefix, a /112 which includes the IPv4 address. =
In the 4rd-E case, the BR checks that the source address in the IPv4 =
header matches that of the IPv6 address. There is therefore no need for =
the BR to know all IPv4 prefixes. At its IPv4 interface, all received =
packets start with one of them. At its IPv6 interface, all packets it =
receives have an embedded address that starts with one of these =
prefixes.=20

> 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.

Regards,
RD



> they can provision each CE individually, and also they are capable to =
distribute the default mapping rule since they should install it into =
the CEs. In that situation, what's the motivation of why the operator =
want to provision with only default mapping rule?
>=20
> cheers,
> --satoru
>=20
>> For this to work, the 4rd-U draft has a bit that, in the hub&spoke =
case, differs between CE-to-BR and BR-to-CE directions. Thus, packets =
sent to a CE take different routes depending on whether sent by a CE or =
a BR.
>>=20
>> I don't see how the equivalent could work with the MAP documents you =
edited.
>> Is it that such a use case is out of scope for MAP?
>> Or did I miss something?
>>=20
>> Cheers,
>> RD
>>=20
>> _______________________________________________
>> Softwires mailing list
>> Softwires@ietf.org
>> https://www.ietf.org/mailman/listinfo/softwires
>=20