Re: [Softwires] Fw: New VersionNotificationfordraft-cui-softwire-b4-translated-ds-lite-04.txt

On 11/4/11 2:38 AM, "Peng Wu" <peng-wu@foxmail.com> wrote:

> Hi Reinaldo,
> 
> I just took a brief look at draft-penno-softwire-sdnat-01,  to get the basic
>  idea. Not sure if I understand correctly.
> 
> This is a quite customized mechanism rather than just "static port set
> allocation in the
>  concentrator". I guess that's why I'm confused by you last email, ha :)
> 
> Regarding the DS-lite case, you kind of encode the port set index into the B4
> IPv6 address,
> and than, achieve statelessness. The difference with the existing stateless
> mechanisms
> is that, you don't encode the public IPv4 address so you don't inform the
> customers
> this information. And you also need double translation to fit in the AFTR NAT,
> which is
> also different from the existing stateless mechanisms.

The double translation is optional. As with other schemes you need to
guarantee uniqueness, which can be achieved in many different ways.

> 
> This is quite interesting. It fits in the specific DS-lite case, but in
> general it's stateless mechanism.
> We kind of fall into different categories and use cases. Actually we have
> discussions on 
> stateless vs. lightweight 4over6 in the Introduction part of our draft. For
> example, think of
> the case when either the B4 IPv6 addresses or the IPv4 address pool are
> scattered. Then the
> the statless mapping rule/algorithm on the AFTR can be quite complicated.

Yes, that is correct. We have approached that and would be happy to discuss.

> 
> 
> --------------
> Peng Wu
>> Hi Reinaldo,
>> 
>> inlines :)
>> --------------
>> Peng Wu
>> 
>>>> The first and the major one is that, if we just take ds-lite and have
>>>> static
>>>> port set allocation in the concentrator, the concentrator still has to keep
>>>> the per-session NAT table and perform the translation, while in lightweight
>>>> 4over6, NAT happens on CPE and the concentrator just perform
>>>> encapsulation/decapsulation, with a per-subscriber mapping table.
>>> 
>>> Per-session NAT is not needed if:
>>> 
>>> - the B4 performs NAT or
>>> - Each host has a unique IP and a known port space.
>>> 
>>> Our implementation performs NAT without any per session state.
>> Could you go a little further into this?
>> I'm actually confused how you do NAT without (source IP,
>> source port, dst IP, dst port) mapping table
>> 
>>> 
>>>> 
>>>> The second one is that in lightweight 4over6, with one-time DHCP/PCP,
>>>> the subscriber learns its public IPv4 address. This brings convenience and
>>>> eases the ALG problem to a certain extent.
>>> 
>>> I think ALG is an application issue and can only be fully solved when all
>>> applications make use of PCP.
>> Well, my point is, if the whole problem is just a local 44NAT(as is in
>> leightweight 4over6),
>> then we already have uPnP, and end host don't need PCP to negotiate with the
>> AFTR 
>> which is  probably a remote, big network device.
>>> 
>>>> In ds-lite with static concentrator
>>>> port allocation, the subscriber still doesn't know its public IPv4
>>>> address/port 
>>>> without per-session PCP process.
>>> 
>>> Yes, that is a good point. We devised an extension to PCP to return the
>>> public IP and port range. Therefore a single message would be needed.
>> Similar idea. But I still need your elaboration on the principle of this
>> none-session-state NAT thing to get the whole picture.
>>> 
>> _______________________________________________
>> Softwires mailing list
>> Softwires@ietf.org
>> https://www.ietf.org/mailman/listinfo/softwires
>> 