Re: New Version Notification for draft-koodli-ipv6-in-mobile-networks-02

[Cameron Byrne <cb.list6@gmail.com>]

On Mon, Apr 19, 2010 at 10:02 AM, Rémi Després <remi.despres@free.fr> wrote:
>
> Le 16 avr. 2010 à 18:45, Koodli, Rajeev a écrit :
>
>> The ID states that the IETF dual-stack model is readily applicable in mobile networks, and that's the likely deployment model for a majority of mobile providers today.
>
> "Likely", yes, but not "recommended" as IPv6-only in the text as is.
>>
>> Towards the end of Section 3.1:
>>
>> " In other words, the IETF's dual-stack model
>>   of separate IPv6 and IPv4 networks is readily applicable to mobile
>>   networks with the support for distinct APNs and the ability to carry
>>   IPv6 traffic on PDP/PDN connections."
>>
>> And in Section 4:
>>
>> "The IETF dual-stack model [RFC4213] can be applied to the mobile networks readily."
>>
>> Your input on dual-stack applies here (specifically Section 3.1).
>>
>> Separately, IPv6-only deployments may be relatively few, but need to be looked into.
>
> "Looked into", I do agree, but not prematurely "recommended".
>
> Among problems I see, one is IMHO very important:
> - E2E transparency is a key feature that IPv6 restores.
> - If DNS64-NAT64 synthesizes IPv6 addresses that hosts don't distinguish today from real IPv6 addresses, this destroys the IPv6 guarantee of e2e transparency.
>
> In my understanding, until all concerned applications do recognize IPv4-embeded IPv6 addresses from real ones, DNS64-NAT64 will be harmful to IPv6, and should be advised against.
>
> Dual-stack deployments (with NAT44 CGNs and guaranteed IPv6 e2e transparency), offer on the other hand a clean IPv6 service that IPv6-only deployments with DNS64-NAT64 can't offer.
>
>
>> In IPv6-only deployments, there can be no IPv4 connectivity (PDN/PDP) at all.  Please see more below.
>
> In sec 3.3, you have (asterisks added):
>   " Hence a service provider may
>   choose to enforce IPv6-only PDN and address assignment for their own
>   subscribers in their Home Networks, see Figure 1.  This is feasible
>   for the newer MNs when the provider's network is "IPv6-ready", which
>   means the network is able to provide IPv6-only PDN support *and
>  IPv6 - IPv4 interworking*  for Internet access."
>
> I therefore understood the considered "IPv6-only" networks as having DNS64-NAT64s (not as having no IPv4 connectivity at all).
>
>> ...
>> I could reword the last sentence to: "For instance, if an LTE deployment is IPv6-only, a roamed 3G UMTS network may not offer IPv6 connectivity"
>
> Isn't it true that the lack of IPv6 connectivity of some 3G UMTS networks is independent from whether LTE networks are dual-standard or not?
>
>
>> ...
>>>> In summary, that is *dual-stack deployments* that must be "encouraged" today.
>>
>> Sure, dual-stack is not only encouraged but the *recommended* model. This is captured in the ID (as I mentioned above):
>>
>> " In other words, the IETF's dual-stack model
>>   of separate IPv6 and IPv4 networks is readily applicable to mobile
>>   networks with the support for distinct APNs and the ability to carry
>>   IPv6 traffic on PDP/PDN connections."
>>
>>>> In my understanding, this is the current IETF stand, and should remain so until more experience is gained.
>>
>> Dual-stack is the recommended model.
>
> Making it very clear will then be an improvement (IMHO).
>
>> "In summary, IPv6-only deployments should be encouraged while considering the roaming and applications issues"
>
> I still can't agree on this because:
> - The market of real IPv6-ony is too limited.
> - IPv6-only + DNS64-NAT64 is harmful to IPv6 e2e transparency.


Why must IPv6 be pure? There is no precedent for IPv6 by nature of its
structure being pure or meaning E2E transparency. NAT-PT has been
around in the IPv6 ecosystem for a long time, so IPv6 addresses
representing IPv4 destinations is by no means new.  I agree that IPv6
is the path to E2E transparency, but IPv6 does not imply e2e by virtue
of the technology. IMHO IPv6-only expedites that journey to e2e.


> - With simple additions in LTE MNs port-restricted public IPv4 addresses can be made available across IPv6-only access networks, which reconciles IPv6 e2e transparency and IPv4 connectivity with an IPv6-only routing plan in LTE access networks. (About this, see also what I answered to Cameron Byrne in http://ops.ietf.org/lists/v6ops/v6ops.2010/msg00609.html).
>
> IMHO, if your draft can be a great informational document if relieved of general "encouragements" to deploy IPv6-only (at least as long as it implicitly goes with DNS64-NAT64), and if noting the conflict between IPv6 e2e transparency and DNS64-NAT64.
>
> Best Regards,
> RD
>
>