Re: 3G multiple PDP context support

[Dan Williams <dcbw redhat com>]

On Mon, 2011-01-10 at 18:49 -0800, Marcel Holtmann wrote:
> Hi Joe,
> 
> > If answered already sorry for the general question  -  searched
> > archives and did not see much.
> >
> > I am wondering if there is support (on any 3G UMTS device) for
> > simultaneous multiple-PDP contexts in NetworkManager.
> >
> > We have Qualcomm-based and other vendor commercial phones and dongles
> > which support multiple-PDP context but no way to have active data over
> > multiple contexts (3 simultaneous is desired).
> 
> with off the shelf USB dongles, I have not seen this working properly
> actually. The only device I know of that can do this is MBM if you use
> the high-speed channel for one and PPP for the other one.
> 
> Of course with cellphone modems like the ISI from Nokia or Infineon and
> even ST-Ericsson the multiple PDP context setup is possible.
> 
> The biggest problem here is that if the dongles are bound to be using
> PPP, then normally no more than one PPP session is support. And thus
> only one active PDP context at a time. Main reason is that the resources
> inside the modem firmware is pretty much limited and PPP is a damn waste
> from resources point of view.
> 
> If they are not using PPP, then normally they only give you one high
> speed Ethernet or point-to-point IP interface. That is not really enough
> to get you to the three you want.
> 
> Also I don't really know if Modem Manager is designed for handling more
> than one PDP context per modem.

It can, though we've been thinking about it in terms of concurrent IPv4
and IPv6 support like we can do for ethernet or wifi.  Some operators do
support IPv6 PDP contexts, and it would rock to have that working
better.  For devices that provide pseudo-ethernet-with-DHCP, perhaps it
magically works with DHCP given the right PDP context type, but for most
devices I doubt it.  It's something that going forward I'm sure we'll
see more of though, so it makes a lot of sense to play around with and
work towards.

Dan