Re: 3G multiple PDP context support

[Marcel Holtmann <marcel holtmann org>]

Hi Dan,

> > > 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.

there will be eventually a IPV4V6 context type coming as well that
properly represents a dual-stack from network point of view.

Some vendors do that magically for you if you don't have that one and
you have to do IP and IPV6 context separately. So the host will see it
as just one Ethernet or IP interface.

In case we have two separate context in the host, I am currently toying
with the idea of just smashing them together via TUN/TAP device or
inside the kernel directly. But this is all just an idea right now.

On the other hand, the number of dongles that support IPv6 right now and
the number of networks providing this to end customers is limited.

Regards

Marcel