RE: 3gpp-analysis-04: use of NAT-PT in IPv6 UE -> IPv4 node

[Pekka Savola <pekkas@netcore.fi>]

On Tue, 22 Jul 2003, Soliman Hesham wrote:
>  > - Use application proxies (such as HTTP gateways, maybe
>  > even TCP/UDP
>  > relays specific to an application) where appropriate to make 
>  > it easier to 
>  > go for IPv6-only UE's at some point if it's the way to go.
> 
> => Again this is already assumed. 
> 
> In draft-elmalki-v6ops ... which was presented in Vienna, 
> we explained the case for NAT-PT. Basically, unlike ethernet, 
> a "3GPP link" cannot be dual stacked. A UE can certainly be 
> dual stacked, but a "link" (PDP context) can only run either
> V4 or V6 but _not_ both. 

Use another PDP context for IPv4.  (Which is what I tried to advocate..)

> For more details on the cost of setting up
> a PDP context see draft-elmalki.

I fail to see anything convincing there;
 - PDP contexts require state in the 3GPP network, and
 - PDP context require radio signalling or a channel

Lots of things require state in the network, including any kind of 
protocol translator.  Protocol translators mitigate the need for radio 
channels, and this is likely to be a problem only in the short term, when 
the number of radio signalling/channels is not a problem (a small number 
of customers).

> The other reason is IMS which mandates IPv6 for signalling 
> and media.

I thought draft-elmalki was primarily focused on solving the IMS 
signalling problem -- which seems strictly separate from this "NAT-PT for 
general consumption" approach, and needs to be settled when we figure out 
which way to go in the IMS Scenario 1.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings