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

[Pekka Savola <pekkas@netcore.fi>]

On Thu, 24 Jul 2003, Karim El-Malki (HF/EAB) wrote:
>  > On Thu, 24 Jul 2003, Karim El-Malki (HF/EAB) wrote:
>  > > You're assuming that roaming is done at L3. Roaming is normally
>  > > done at L2 so for example ISATAP is a relevant option.
>  > 
>  > (I think you should elaborate on "normally")
> 
> According to the 3gpp standard.

Are there known (or planned) deviations from this standard?

>  > OK.  If roaming is done at L2, then IP addresses etc. should 
>  > stay the same
>  > when you roam, right?  Then IPv6 addresses will stay too, 
>  > right?  So, why
>  > do you need ISATAP there then?
> 
> Imagine a situation in which you're roaming to another
> operator's network. The roaming user requests v6 connectivity
> (PDP Context) in the new network. If the new network doesn't
> support it, the roaming user won't get v6 connectivity.

Ok; this is not necessarily a huge problem in itself.

But let me try to rephrase this:

Imagine a situation in which you're moving under another GGSN in your 
operator's network.  The user requests v6 connectivity
(PDP Context) in the network. If the network doesn't
support it, the user won't get v6 connectivity.

I.e., to be able to use v6 everywhere under your own operator's network, 
is it required that all GGSN's in that operator's network support IPv6 PDP 
contexts?

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.

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.

> The PDP Context is a special L2 as described in RFC 3314.

Ok, let me try to clarify several ambiguous points: (there are probably 
more but from the top of my head)

Does the IP address of the UE change when it roams to another network?
Does the GGSN always change to a GGSN of the another network?
  If not, how is IP address kept the same?
  If yes, is mobility (in the meaning of "connection 
          survivability") between roaming networks a non-goal as it can't 
          work at PDP context layer?

When the user moves inside the same operator's network does the IP address 
change? (I don't think so)
 - Does the GGSN change? (I don't think so)
    If yes, how does mobility work then?

What determines which GGSN you end up using in the operator's network?
 - How does this work in a network where some GGSN's are v6-capable and 
some not?

Figure 3 (typo: should be fig 4) in page 11 seems to indicate that UE can
have multiple PDP contexts, to multiple ISPs.  As long as UE opens the PDP
context to his own ISP which supports v6, you're fine.  But can the UE do 
that?

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