*** QuickStart ***

REQUIREMENTS

Linux
OpenGGSN was developed and tested using Redhat 7.1 and Redhat
7.2. It should run also on other Linux distributions as well as
FreeBSD and Solaris, but this is untested. Please tell me of any
testing results.

Tun
Both ggsn and sgsnemu uses the tun package. You need at least tun
version 1.1. See http://vtun.sourceforge.net/tun/ for instructions on
installation. Tun is included in the kernel from early version 2.4, so
you will not normally need to install it. For Redhat 7.1 and 7.2 you
do however need to do the following:
mkdir /dev/net
mknod /dev/net/tun c 10 200
Add this line to /etc/modules.conf: alias char-major-10-200 tun 
depmod -a


COMPILATION and INSTALLATION
./configure
cd gtp
make
make install
cd ..
make
make install
Add /usr/local/lib to /etc/ld.so.conf
Run ldconfig


RUNNING

sgsnemu
Edit the configuration file sgsnemu.conf found under
openggsn/examples. Use sgsnemu -h for a list of available options.
Start the emulator using the command:

  sgsnemu -c examples/sgsnemu.conf -l 10.20.30.50 -r 10.20.30.40

This will cause the sgsn emulator to bind to local address 10.20.30.50
and connect to the ggsn found at 10.20.30.40. It will first send off
an ECHO_REQUEST message. After this it will attempt to establish a pdp
context. If successful it will create a local interface and set up
routing. Now you should be able to ping through the connection. Use a
network analysator such as ethereal to monitor the traffic.

ggsn
Edit the configuration file ggsn.conf found under
openggsn/examples. Use sgsnemu -h for a list of available options.
Start the ggsn using the command:

  ggsn --fg -c examples/ggsn.conf -l 10.20.30.40 --statedir .

This will run the ggsn in foreground using the local interface
10.20.30.40. Of cause you can use sgsnemu to test the GGSN.


SUPPORT
If you have any questions drop me a line at jj@openggsn.org.


*** Features ***

OpenGGSN is an open source implementation of GPRS Support Nodes
(GSNs). It implements the GPRS tunneling protocol (GTP) version 0.

OpenGGSN provides 3 components:
* gtplib
* ggsn
* sgsnemu

gtplib
This library contains all functionality relating to the GTP
protocol. Use this libraty if you want to implement your own
GSN. Currently gtplib supports GTPv0. At the moment no interface
documentation is available for download.

ggsn
The ggsn implements a Gateway GPRS Support Node. The GGSN is a small
application which is provided in order to test and demonstrate the use
of gtplib. It is fully compliant to the 3GPP standards, but lacks
important functionality such as charging and management. Use this
application as a starting point if you want to build your own GGSN
with your own fancy VPN, management and charging functionality.

sgsnemu
This application emulates a Serving GPRS Support Node (SGSN). sgsnemu
enables you to test your 3GPP core network without the need to invest
in a 3G radio access network. An important application of sgsnemu is
the testing of roaming connectivity through a GPRS roaming exchange.


*** Required software ***

TUN  (http://vtun.sourceforge.net/tun/)

Both ggsn and sgsnemu uses the tun package. You need at least tun
version 1.1. See the above web page for instructions on
installation. Tun is included in the kernel from early version 2.4, so
you will not normally need to install it. For Redhat 7.1 and 7.2 you
do however need to do the following:
mkdir /dev/net
mknod /dev/net/tun c 10 200
Add the following line to /etc/modules.conf: alias char-major-10-200 tun 
depmod -a


GENGETOPT (http://www.gnu.org/software/gengetopt/gengetopt.html)

Gengetopt is required if you want to change the options defined in the
cmdline.ggo source file. You need at least gengetopt version 2.8. If
you are just going to compile the programs you don't need gengetopt.

To use gengetopt for the ggsn do the following:
cd ggsn
gengetopt < cmdline.ggo --conf-parser

To use gengetopt for the sgsnemu do the following:
cd sgsnemu
gengetopt < cmdline.ggo --conf-parser


*** Compilation and Installation ***

To generate everything:
See http://sources.redhat.com/autobook/autobook/autobook_25.html#SEC25
 1 edit configure.in
 2 run aclocal
 3 run autoheader
   (run automake --add-missing)
 4 run automake
 5 run autoconf
 6 run ./configure
 7 rin make clean
 8 run make
   (First time you run make it will complain that it can not find gtp.
    Ignore the warning, gtp will get installed when you run make install)
 9 run make install
10 Add /usr/local/lib to /etc/ld.so.conf
11 run ldconfig


On RedHat add /usr/local/lib to /etc/ld.so.conf
http://www.dwheeler.com/program-library/Program-Library-HOWTO/shared-libraries.html

*** Running ggsn ***

Use ggsn -h for a list of available options. All options available on
the command line can also be given in a configuration file. See
examples/ggsn.conf for the format of this file.

*** Running sgsnemu ***

Use sgsnemu -h for a list of available options. All options available
on the command line can also be given in a configuration file. See
examples/sgsnemu.conf for the format of this file.

If you want to test a GRX roaming connection you will need to do the
following:

1) Install sgsnemu on a Linux Box. See under installation above.

2) Connect your Linux box with sgsnemu installed to the GPRS core
network. Use the same LAN switch as the one your SGSN is connected
to. You also need a free IP address that can be used by sgsnemu.

3) You need to configure networking in terms of interface address,
subnet mask and default route. See the Linux Networking HOWTO for
details.

4) Launch sgsnemu with something like:

     sgsnemu --fg --listen 10.20.30.50 --remote 10.20.30.40 --dns 10.20.38.51 --timelimit 10 --contexts 0 

sgsnemu will print something like the following on the screen:

  Using DNS server:      10.20.38.51 (10.20.38.51)
  Local IP address is:   10.20.30.50 (10.20.30.50)
  Remote IP address is:  10.20.30.40 (10.20.30.40)
  IMSI is:               240011234567890 (0x98765432110042)
  Using APN:             internet
  Using MSISDN:          46702123456

  Initialising GTP library
  OpenGGSN[1823]: GTP: gtp_newgsn() started
  Done initialising GTP library

  Sending off echo request
  Waiting for response from ggsn........

  Received echo response. Cause value: 0

This is quite good. It means that you managed to send off an echo
request to a remote GGSN, and it was friendly enough to answer you. If
you did not get an echo response it means that something is wrong
either with your setup OR with the GRX connection OR with your roaming
partners connection.

If the above went well you might want to try to establish a PDP
context to the remote GGSN. Note that you should be carefull when
establishing PDP contexts using sgsnemu as each established PDP
context will result in a Charge Detail Record (CDR) being generated by
the GGSN. You should use real IMSI and MSISDN from a valid test SIM
card. Otherwise some poor customer might get charged for your
testing. Also note that you are establishing a connection to the Gi
netowrk, so please be carefull not to route internet traffic onto the
GPRS core network! Assuming you know what you are doing:

     sgsnemu --fg --listen 10.20.30.50 --remote 10.20.30.40 --dns 10.20.38.51 --timelimit 10 --contexts 1 --apn internet --imsi 240011234567890 --msisdn 46702123456 --net 192.168.0.0 --mask 255.255.255.0

sgsnemu will print something like the following on the screen:

  Using DNS server:      10.20.38.51 (10.20.38.51)
  Local IP address is:   10.20.30.50 (10.20.30.50)
  Remote IP address is:  10.20.30.40 (10.20.30.40)
  IMSI is:               240011234567890 (0x98765432110042)
  Using APN:             internet
  Using MSISDN:          46702123456

  Initialising GTP library
  OpenGGSN[1838]: GTP: gtp_newgsn() started
  Done initialising GTP library

  Sending off echo request
  Setting up PDP context #0
  Waiting for response from ggsn........

  Received echo response. Cause value: 0
  Received create PDP context response. Cause value: 128
  Setting up interface and routing
  /sbin/ifconfig tun0 192.168.0.1
  /sbin/route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.0.1


Now a context is established to the remote GGSN. The IP address of the
context is 192.168.0.1. If you specified the correct --net and --mask
you should be able to ping a known address on the Gi network of the
roaming partner. You should even be able to do web browsing through
the PDP context.

Note however that you probably need to adjust your routing tables, so
that you make sure that all GRX traffic is routed to the GPRS core
network and everything else through the PDP context. The proper way to
do this is to use policy routing. Also note that you are effectively
connecting the same computer to both the Gn and Gi network, so please
be carefull not to route internet traffic onto the GPRS core network
and please protect yourself against hackers! For this reason it is
advised to always use --contexts 0 when testing a live network.

After --timelimit seconds the PDP context is disconnected with the
following messages from sgsnemu:

  Disconnecting PDP context #0
  Received delete PDP context response. Cause value: 128
  Deleting tun interface