wiki:OpenBSC_GPRS

OpenBSC GPRS/EDGE Setup page

Pre-requisites

  • A nano BTS with GPRS or EDGE support. BS-11 are not supported (yet?)
  • A compiled GGSN from OpenGGSN (make sure to use the osmocom version. git://git.osmocom.org/openggsn.git )
  • A working and up-to-date OpenBSC (see Building_OpenBSC)
    • You will need to (re-)build it after having installed OpenGGSN so that the libgtp is detected and the SGSN binary osmo-sgsn built.
  • A custom SIM for your network
    • Currently osmo-sgsn refuses all roaming, so you need a SIM that matches your custom MCC/MNC network

Setup

First a little picture to illustrate the different elements and their interactions :

Compiling OpenBSC with [E]GPRS

The guide below was tested on Ubuntu 11.10 but should work on Debian as well. This guide uses /root for everything.

First you need to download all dependencies:

apt-get install libdbi0-dev libdbd-sqlite3 libtool autoconf git-core pkg-config make libortp-dev

Next, download the OpenGGSN source code:

cd /root
git clone git://git.osmocom.org/openggsn.git

Compile OpenGGSN:

cd /root/openggsn
autoreconf; automake --add-missing; autoreconf; autoconf; automake; ./configure --prefix=/usr/local; make -j 2; make install

Now download everything else:

cd /root
git clone git://git.osmocom.org/libosmocore.git; git clone git://git.osmocom.org/libosmo-abis.git; git clone git://git.osmocom.org/libosmo-netif.git; git clone git://git.osmocom.org/openbsc.git

Compile the rest:

cd /root/libosmocore; autoreconf -fi; ./configure; make; make install; ldconfig
cd /root/libosmo-abis; autoreconf -fi; ./configure; make; make install; ldconfig
cd /root/libosmo-netif; autoreconf -fi; ./configure; make; make install; ldconfig
cd /root/openbsc/openbsc; autoreconf -fi; export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig; ./configure; make

You should now have a working copy of ggsn, osmo-sgsn and osmo-nitb on your machine.

OpenBSC configuration

The first step is to configure OpenBSC for gprs support. Add this to the network/bts node in openbsc.cfg:

gprs mode gprs
gprs routing area 0
gprs cell bvci 2
gprs nsei 101
gprs nsvc 0 nsvci 101
gprs nsvc 0 local udp port 23000
gprs nsvc 0 remote udp port 23000
gprs nsvc 0 remote ip 192.168.0.128

The gprs nsvc 0 remote entries 192.168.0.128:23000 is the IP/port of the machine running the SGSN as seen from the BTS. It will be sent by OpenBSC to the BTS in the configration phase and the BTS will connect back to the SGSN.

The second step is to allocate some timeslots to packet data. For this, just change the 1 or more network/bts/trx/timeslot nodes using :

phys_chan_config PDCH

Osmocom SGSN configuration

Here's a sample SGSN configuration file osmo-sgsn.cfg with some explanations :

!
! Osmocom SGSN configuration
!
!
line vty
 no login
!
sgsn
 gtp local-ip 192.168.1.128
 ggsn 0 remote-ip 192.168.1.129
 ggsn 0 gtp-version 1
!
ns
 timer tns-block 3
 timer tns-block-retries 3
 timer tns-reset 3
 timer tns-reset-retries 3
 timer tns-test 30
 timer tns-alive 3
 timer tns-alive-retries 10
 encapsulation udp local-ip 192.168.0.128
 encapsulation udp local-port 23000
 encapsulation framerelay-gre enabled 0
!
bssgp
!
  • The gtp local-ip entry is the local IP the SGSN will bind to.
  • The ggsn 0 remote-ip entry if the remote IP of the GGSN. The SGSN will connect to it.
  • Those two IPs must be different even if you're running both processes on the same machine. A solution for that is to put several IP aliases on the same network interface or use the loopback interface.
  • The encapsulation settings must be the same IP/port than you've setup in openbsc.cfg

OpenGGSN configuration

The ggsn.conf file is pretty well documented. What is mostly of interest here is :

  • The configuration of the GTP link. (Must match the ggsn 0 remote-ip entry in osmo-sgsn.cfg)
# TAG: listen
# Specifies the local IP address to listen to
listen 192.168.1.129
  • The configuration given to phones, IP pool & DNS.
# TAG: dynip
# Dynamic IP address pool.
# Used for allocation of dynamic IP address when address is not given
# by HLR.
# If this option is not given then the net option is used as a substitute.
dynip 192.168.254.0/24

# TAG: pcodns1/pcodns2
# Protocol configuration option domain name system server 1 & 2.
pcodns1 208.67.222.222
pcodns2 208.67.220.220

Network configuration

You will also need to configure some networking rules to allow connectivity from tun0. Look up linux networking/nat howtos on google. The basic setup for testing only in a safe environment would be :

bash# echo 1 > /proc/sys/net/ipv4/ip_forward
bash# iptables -A POSTROUTING -s 192.168.254.0/24 -t nat -o eth0 -j MASQUERADE

(replace eth0 by the interface providing your machine connectivity)

Running

Just start the three processes :

  • ggsn
  • osmo-sgsn
  • osmo-nitb

You can access vty from

Last modified 5 months ago Last modified on Jun 18, 2014, 12:21:54 PM

Attachments (2)

Download all attachments as: .zip