GPRS - fairly off topic

Jon Schneider jon at
Thu Sep 5 20:59:10 BST 2002

I may be shortly asked by a colleague to do something useful with a pair of GPRS 
modules (Erickson GM47 and a Siemens MC35) and have a number of questions. 
Posting here seems like my best bet to get some knowledgeable answers. (I don't want 
to be told to click on "My Computer".)

My colleague seems to think the modules talk PPP but has not managed to get 
Vodafone's ConnectMe software (designed for phones) to talk to them. I don't know 
whether this should work or not. I'm thinking about using Brian's ppp to experiment. 
Ultimately we'll be lashing these modules to small micros along with GPS and other 
stuff. Then I'll need to come up with some lean mean code which is just enough to do 
the PPP and compose UDP packets.

Does being connected through a typical (well Vodafone's or Orange's) GPRS service 
give one an IP (v4) address ?  If so won't the operators rapidly run out of them ? Or are 
they NATing or proxying ? Obviously IPv6 would be better. What exactly is the cost 
based on (amount of TCP/UDP data or the whole PPP frame) ? What's to stop a third 
party squirting junk data and running up a huge bill ?


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