RE: 3gpp-analysis-04: Transition mechanisms at UEs; 3GPP IPv6 dep loyment (fwd)

["Karim El-Malki (HF/EAB)" <karim.el-malki@ericsson.com>]

A late reply to Pekka below.
Hope this can help in closing the loop on the tunnelling issue.

 > On Thu, 24 Jul 2003, Karim El-Malki (HF/EAB) wrote:
 > >  > Or let me phrase this differently:
 > >  > 
 > >  >  Would roaming with 3GPP UE work if the roaming agreements 
 > >  > would include 
 > >  >  an indication whether the foreign network supports the same 
 > >  > PDP context 
 > >  >  types as the original network.
 > >  > 
 > >  > I.e. the user can prefer those roaming partners which 
 > >  > provide the services 
 > >  > they want.  That should be enough of an economic incentive.
 > > 
 > > Basically the UE won't know until it tries to activate
 > > a v6 connection and it gets refused.
 > 
 > This seems like a potentially fatal design flaw.

When I plug into Ethernet or WLAN I don't know if the network
supports IPv6 until I get an RA. In this case we know before
activating the PDP Context i.e. L2 link. So this doesn't look like
a flaw to me, although it could be improved with what you
write above.

 > 
 > If UE's were to run PPP PDP Contexts, could the lack of IPv6 
 > support in 
 > remote SGSN's/GGSN's be avoided ?

You could do that, but it would be an overkill IMO to run PPP
over wireless. Since we're dealing with an expensive bandwidth
limited link it's not an attractive alternative.

 > 
 > >  > Or, i.e. we define that "roaming" is not "true roaming" 
 > >  > unless you provide 
 > >  > the support for the same PDP context types; that is, there 
 > >  > is "partial 
 > >  > roaming" as of today and "real roaming" of tomorrow.
 > >  > 
 > >  > IMHO, it seems ill-advised to call something "roaming" when 
 > >  > they fail to 
 > >  > provide critical infrastructure capabilities the users need.
 > > 
 > > Some people would see voice, IPv4 or MMS as critical so I don't
 > > think it makes sense to get into a discussion here on what the word
 > > "roaming" should mean.
 > 
 > Is there a significant number of roaming partners where 
 > voice, IPv4 or MMS 
 > are not supported (in regions where some other potential 
 > roaming partners 
 > would provide support for them)?  Otherwise your analogy 
 > does not seem 
 > fitting.

For example today operators have gprs (IPv4) roaming agreements
with certain operators and only voice with others. 

 > >
 > > L2 tunnelling back to the home network.
 > 
 > So, as the GGSN does not always change, there should be a way to 
 > keep alive the association with the local GGSN?

This is done using 3gpp protocols.
 
 > If you use IPv6 PDP context to a local GGSN, move over to 
 > another country 
 > and 3GPP operator but don't switch off your UE -- retaining 
 > your old GGSN 
 > -- does the IPv6 still work through the IPv6 PDP context through L2 
 > tunneling?  If not, why not?

Don't think so. You would try to set up this type of handoff (which
involves passing PDP Context info from old to new SGSN) and the local
SGSN would reject it if it didn't understand PDP type IPv6.

 > If SGSN doesn't support IPv6 PDP contexts but GGSN does, 
 > you're out of 
 > luck? (without tunneling by the UE)

Yes. There's also another element involved (HLR) which needs
to have some knowledge of IPv6 to authorise the user to use
the IPv6 service. Basically the GGSN is not the only device
that needs to know what IPv6 is in order for things to work,
although it is the most important one from our IP-centric point
of view.

If you're in this special case (which will hopefully become
rare in future) and you want to have a way of using IPv6 services
then tunnelling is an attractive solution.

 > I'm not sure if my question got across, because I don't 
 > understand the 
 > answer in that context.
 > 
 > So, let's try again:
 > 
 > How exactly can UE's open multiple PDP _primary_ contexts to 
 > different operators?  Is there anything in the capabilities of the 
 > network(s) which may hinder your possibilities to open PDP 
 > contexts to 
 > different ISPs?

For one thing you cannot open multiple connections to different
operators at the same time. Apart from that you can try and connect
to any operator which has roaming agreements with your home operator.

 > When you're roaming, couldn't you just try opening IPv6 PDP 
 > context, and 
 > if it fails, try some other roaming partner (if available) 
 > and try to open 
 > an IPv6 PDP context there too?

You could if there are other roaming partners. But you could
also just be wasting your time and it does waste quite a
bit of time to detect the networks, pick an operator, check
connectivity, detect again etc.

 > Or even try opening PDP contexts simultaneously (would be 
 > more costly, I suppose -- depending on whether the billing 
 > starts after or 
 > before the PDP context activation is successful; in this 
 > scenario, it's 
 > the latter)?

You can't do that. You can only be connected to one operator at
a time.

/Karim