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From: Satoru Matsushima <satoru.matsushima@gmail.com>
In-Reply-To: <2698466B-C775-4534-B60C-F4C0C2576B4A@laposte.net>
Date: Tue, 7 Feb 2012 15:26:41 +0100
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Message-Id: <91E90DC9-99EC-44C2-89A9-7ED42E83701C@gmail.com>
References: <554901A7-F23C-4197-8783-85D51B502EA3@laposte.net>
 <80C2DFB3-0E21-44F2-9FCA-F0B4CF88DA22@gmail.com>
 <2698466B-C775-4534-B60C-F4C0C2576B4A@laposte.net>
To: =?utf-8?Q?R=C3=A9mi_Despr=C3=A9s?= <despres.remi@laposte.net>
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

On 2012/02/07, at 14:03, R=E9mi Despr=E9s wrote:

>=20
> Le 2012-02-07 =E0 13:07, Satoru Matsushima a =E9crit :
>=20
>> 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?
>=20
> 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
>=20

It looks like that you treat default mapping rule as a basic mapping =
rule to check source address consistency on the BR. It should work, and =
the MAP too.


>> I think that operators who already deploy such dual-stack network is =
supposed that they have address mapping table,
>=20
> 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.=20

cheers,
--satoru

>=20
> Regards,
> RD
>=20
>=20
>=20
>> 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
>=20