Cellular Network Infrastructure » Core Network (CN) » OsmoGGSN (former OpenGGSN)

h1. OsmoGGSN and Linux Kernel accelerated GTP-U

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OsmoGGSN has support to use the Linux kernel GTP-U code to accelerate the data/user plane while still implementing the control plane (GTP-C) in userspace in OpenGGSN.

For more information about the Linux kernel GTP-U code, please see [[linux-kernel-gtp-u:]]

h2. Building OsmoGGSN with kernel which has GTP-U support

At the time of writing (2017-01-09) of this wiki, below listed distributions have support of GTP kernels :

* Debian 4.9.1-1~exp1 - Debian's latest experimental build 

* Ubuntu 16.10 kernel 4.8

* OpenSUSE Tumbleweed (stable) 4.8 (.12)

* Fedora 25 kernel 4.8 

Following two Debian kernels do not activate GTP kernel module during build: 4.8.0 and 4.9.0.

Check if package @libc-ares-dev@ is installed and if not please add it.

Ubuntu 16.10, kernel 4.8.0-30-generic is used. 

h3.  Installing dependencies and build library @libosmocore@

You can install required dependency packages with:

<pre>

sudo apt install libtalloc-dev libpcsclite-dev

</pre>

Please follow instructions provided at [[cellular-infrastructure:Build from source]] in order to install libosmocore

h3.  Installing dependencies and build library @libgtpnl@

You can install dependencies with:

<pre>

sudo apt install libmnl-dev

</pre>

Then build libgtpnl like this

<pre>

git clone git://git.osmocom.org/libgtpnl.git

cd libgtpnl

autoreconf -fi

./configure

make

sudo make install

sudo ldconfig

</pre>

h3. osmo-ggsn

Build OsmoGGSN like this:

<pre>

git clone git://git.osmocom.org/osmo-ggsn.git

cd osmo-ggsn

./configure --enable-gtp-linux

make

sudo make install

sudo ldconfig

</pre>

Following message is shown at end of the command: @ ./configure --enable-gtp-linux@ 

<pre>

OsmoGGSN Configuration:

  GTP Linux kernel support:			yes

</pre>

This means that appropriate header files are available.

h2. Using OpenGGSN with kernel which has GTP-U support

In order to find out whether gtp.ko module is available we can enter following command:

<pre>

find /lib/modules/`uname -r` -name gtp.ko

</pre>

Output below shows that gtp.ko module is present:

<pre>

/lib/modules/4.8.0-30-generic/kernel/drivers/net/gtp.ko

</pre>

We are loading module gtp from kernel issuing command: <pre>sudo modprobe gtp</pre> 

when you enter: 

<pre>

lsmod | grep gtp

</pre>

then more information about gtp and related udp tunnel can be obtained:

<pre>

gtp                    28672  0

udp_tunnel             16384  1 gtp

</pre>

Some helpful tools are available in: @libgtpnl/tools@

you can get more details about gtp-tunnel, entering command from the OpenGGSN shell:

<pre>

sudo ./gtp-tunnel list

</pre>

Output will be similar to:

<pre>

version 1 tei 1/0 ms_addr 192.168.0.2 sgsn_addr 127.0.0.2

</pre>

Note: OsmoGGSN is started by: 

<pre>

sudo osmo-ggsn -c osmo-ggsn.conf

</pre>

Related output should be similar to the one shown below: 

<pre>

FIXME

</pre>

You can now start to establish PDP contexts to your new osmo-ggsn instance, from [[OsmoSGSN:]], @sgsnemu@ or third-party SGSNs