GPRS IP Networking

Samuel Melrose sam at
Mon May 19 14:06:10 CEST 2008

Since you're talking about tunnels, etc. I know it wasn't what you  
were originally hoping for, having to have a server (I'm guessing)...
But as Tim says an SSH tunnel and the script checking would waste a  
lot of energy... I don't know if it is something that could be done,  
but I'm certainly going to try it when I get mine... Is openvpn. Not  
sure if this is any use at all, but it certainly (if you have  
somewhere you can set up a server) will do everything for you if its  
configured.. You'd just have to watch the data charge for the keep  
alive packets? But this way, its all encrypted, and well... Its not an  
external IP address, but you can certainly bridge it to another  
network, and all sorts.
This would solve all the worry about the NAT pool or how they do their  
IP networking, as it would just make a connection, and from my  
experience with using it before if it is set up to do so, do what  
every it takes to keep that connection alive, and therefor, simple.

Would just involve having tun/tap in the kernel, and cross-compiling  
openvpn to the platform. And from what I understand, openssl is  
already included?

Please correct me if I am wrong, quite new to Openmoko, and not quite  
sure what actually comes packaged.

Thanks and all the best,
Samuel Melrose
sam at

On 19 May 2008, at 12:35, Tim wrote:

> Hi,
> I tried it two years ago with the german provider "base" (they had  
> the first UMTS/GPRS flatrate). They gave my device some internal IP  
> address. To get my device accessible from the internet I wrote a  
> script that build an SSH tunnel (with port forwarding from server to  
> mobile device) from the mobile device to my server on the "real"  
> internet. Worked pretty well, but it's not really efficient that  
> way. With that kind of TCP connection and a script checking if the  
> tunnel is still valid you will waste a lot of energy.
> -tim
> Steven Kurylo schrieb:
>> Does someone know how IP addresses are handed out on the cellular
>> network?  Do they give each phone an IP address, or do they do  
>> NAT?  I
>> want to know if I'll be able to connect to my freerunner over GPRS,
>> say I wanted to ssh into it.
>> I've been searching the internet and haven't found an answer.  I
>> connected to my website with my blackberry and saw different IP
>> addresses for different requests; makes me think they have an  
>> outgoing
>> NAT pool.  Of course this could also be carrier dependent.
>> Thanks.
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