Today marks the day where finally, after months of (non-full-time) work, I have made the first successful HTTP connection through my own GPRS/EDGE network.
Ever since we started to seriously get into OpenBSC to run GSM networks, I've been looking forward to running GPRS networks, too. What most people don't know: GPRS is radically different from GSM. It basically only shares the frequencies and timeslot architecture of the physical layer, while having it's own layer1, layer2 and various other protocol layers. Also, its signalling and data completely bypass the usual BSC and MSC components of a GSM core network.
So what I've been working on is now called OsmoSGSN. Using OpenBSC, you can provision an ip.access nanoBTS (or any other BTS with a Gb Interface) to broadcast the GPRS/EDGE capabilities to the handsets. The BTS then establishes the Gb interface (consisting of NS and BSSGP) to the SGSN.
The SGSN takes care of GPRS Mobility Management (GMM) and Session Management(SM) in the signalling plane, as well as the LLC + SNDCP protocol layers. On the other end, it uses the GTP protocol to connect to a GGSN. In our case, this is the OpenGGSN project which I recently adopted.
OpenGGSN then creates a virtual network device (tun0), through which the actual IP packets are entering/leaving the GPRS network. From there you can route and/or NAT them just like any other IP packets.
The current code is still incomplete in many places and known to be unstable. But it's really rewarding that after a long time of development, layer after layer of the stack, finally actual TCP/IP can be provisioned to phones.
The code is in the current master of the openbsc git repository, but I don't think there's much point in trying it just yet. I suppose in a week from now things should be much more stable.