I don't know much about mobile network ISPs’ typical protocol stacks, nor about 3G’s higher-level protocols either.
Does anyone know what service providers such as Three and EE impose upon you in terms of (i) MTU and (ii) protocol support or service blocking?
I use Andrews and Arnold’s IPv4 over 3G (no voice) service which runs over the Three network. They give you one static IPv4 address per account, which is enough for the one iPad that I use with the account, and if I add more machines I just add more accounts and so get one more IPv4 each.
For some reason, they haven't managed to get IPv6 running over it (natively), although I could set it up with proto 41 tunnelling, except I'm using an iPad so I would have to place a router in front of the iPad which would be very messy. Same if I ran L2TP instead.
Does anyone know if (iii) PPP runs over these ISPs’ systems? I'm assuming not, otherwise IPv6 would presumably just work. Could someone deliver (non-tunnelled) Ethernet instead of IP?