Configuration:

• Install pppd
• Set up /etc/ppp/peers/s45_gprs something like this:

  # These are the options to dial out to your default service provider.
  # Please customize them correctly. Only the "provider" file will be
  # handled by poff and pon (unless with extra command line arguments).
  
  # You usually need this if there is no PAP authentication
    noauth
  # I've added the export commands to set up $DNS1 & $DNS2 with indigo DNS servers
  # The chat script (be sure to edit that file, too!)
    connect "export DNS1=62.40.32.33; export DNS2=62.40.32.34; /usr/sbin/chat -v -f /etc/chatscripts/s45_gprs"
  # Set up routing to go through this PPP link
    defaultroute
  # Default modem (you better replace this with /dev/ttySx!)
    /dev/ttyS0
  # Speed
    115200
  # Keep modem up even if connection fails
    persist
  # Tell pppd to set up DNS servers set above
    usepeerdns
  # leave username blank
    user ""
  

• Create /etc/chatscripts/s45_gprs something like the following:

  TIMEOUT 45
  ABORT BUSY
  ABORT "NO CARRIER"
  ABORT ERROR
  "" 'ATE1'
  OK AT+CGDCONT=1,"IP","internet"
  OK ATD*99***1#
  CONNECT \d\c
  

  Please note, these settings are specific to the O2 Ireland Network. my-siemens.com has a pdf with the details for many networks.
  
  
• To connect type the following:

  gavin@linux gavin> pon s45_gprs
  

  or if pon is not a known command

  gavin@linux gavin> pppd call s45_gprs
  

  It's necessary here to have enabled GPRS on the phone in Setup->Connectivity first.
  
  
• To disconnect type the following:

  gavin@linux gavin> poff s45_gprs
  

  or

  gavin@linux gavin> killall pppd