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

[Soliman Hesham <H.Soliman@flarion.com>]

 > > 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

=> There is also the time it takes to setup a PDP
context, which is significant.

 > 
 > Lots of things require state in the network, including any kind of 
 > protocol translator.  Protocol translators mitigate the need 
 > for radio 
 > channels, 

=> This is not related to radio channels, it's related
to the time and the resources consumed in the network.

   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).

=> I don't understand the above statement. There is no
relationship between the resources/time consumed to setup
a context and the 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.

=> They are tightly coupled. The draft first makes 
the case for NAT-PT and then goes into how IMS would
use it. If IMS requires translation anyway, NAT-PT
will be used. Everything is running in the same
network. 

Hesham